MAX1700, MAX1701
19-4759; Rev 1; 1/99
L
MANUA
ION KIT HEET
T
A
U
L
EVA
TA S
WS DA
FOLLO
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
Features
The MAX1700/MAX1701 are high-efficiency, low-noise,
step-up DC-DC converters intended for use in batterypowered wireless applications. They use a synchronous-rectified pulse-width-modulation (PWM) boost
topology to generate 2.5V to 5.5V outputs from battery
inputs such as one to three NiCd/NiMH cells or one LiIon cell. Both devices have an internal 1A, 130mΩ Nchannel MOSFET switch and a 250mΩ P-channel
synchronous rectifier.
♦ Up to 96% Efficiency
With their internal synchronous rectifier, the MAX1700/
MAX1701 deliver 5% better efficiency than similar nonsynchronous converters. They also feature a pulsefrequency-modulation (PFM) standby mode to improve
efficiency at light loads, and a 3µA shutdown mode.
♦ External Clock or Internal 300kHz Oscillator
The MAX1700/MAX1701 come in 16-pin QSOP packages (which occupy the same space as an 8-pin SO).
The MAX1701 includes two comparators to generate
power-good and low-battery warning outputs. It also
contains a gain block that can be used to build a linear
regulator using an external P-channel pass device.
For higher-power outputs, refer to the MAX1703. For
dual outputs (step-up and linear regulator), refer to the
MAX1705/MAX1706. For an on-board analog-to-digital
converter, refer to the MAX848/MAX849.
♦ 1.1 VIN Guaranteed Start-Up
♦ 0.7V to 5.5V Input Range
♦ Up to 800mA Output
♦ Step-Up Output (adjustable from 2.5V to 5.5V)
♦ PWM/PFM Synchronous-Rectified Topology
♦ 3µA Logic-Controlled Shutdown
♦ Power-Good Output (MAX1701)
♦ Low-Battery Comparator (MAX1701)
♦ Uncommitted Gain Block (MAX1701)
Ordering Information
PART
MAX1700EEE
MAX1701EEE
TEMP. RANGE
PIN-PACKAGE
-40°C to +85°C
-40°C to +85°C
16 QSOP
16 QSOP
The MAX1701 evaluation kit is available to speed design
time.
Typical Operating Circuit
Applications
Digital Cordless Phones
PCS Phones
Personal Communicators
Palmtop Computers
Wireless Handsets
Two-Way Pagers
Hand-Held Instruments
INPUT
0.7V TO 5.5V
Pin Configurations
MAX1700
ON
TOP VIEW
I.C. 1
16 I.C.
I.C. 2
15 POUT
REF 3
14 OUT
CLK/SEL 4
MAX1700
OUTPUT
3.3V OR ADJ
UP TO 800mA
OFF
ONA
ON
ONB
LX
OFF
PWM
PFM
OR
SYNC
CLK/SEL
POUT
13 LX
12 PGND
GND 5
I.C. 6
11 FB
REF
ONB 7
10 I.C.
FB
ONA 8
9
OUT
GND PGND
I.C.
QSOP
I.C. = INTERNAL CONNECTION. LEAVE OPEN OR CONNECT TO GND
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
MAX1700/MAX1701
General Description
MAX1700/MAX1701
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
ABSOLUTE MAXIMUM RATINGS
ONA, ONB, OUT, AO, POK, LBO to GND...................-0.3V, +6V
PGND to GND.....................................................................±0.3V
LX to PGND.....................................................-0.3V,VPOUT+0.3V
CLK/SEL, AIN, REF, FB, LBP, LBN, POUT to GND............-0.3V,
VOUT+0.3V ...................................................................................
Continuous Power Dissipation (TA=+70°C)
16-QSOP (Derate 8.30mW/°C above +70°C) ...............667mW
Operating Temperature Ranges
MAX1700EEE, MAX1701EEE ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(CLK/SEL = ONA = ONB = FB = PGND = GND, OUT = POUT, VOUT = 3.6V (Note 6); MAX1701: AIN = LBN = GND, LBP = REF,
TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
0.7
5.5
V
0.9
1.1
V
DC-DC CONVERTER
Input Voltage Range (Note 1)
Minimum Start-Up Voltage
(Note 2)
ILOAD < 1mA, TA = +25°C
Frequency in Start-Up Mode
VOUT = 1.5V
40
150
300
kHz
Output Voltage (Note 3)
VFB < 0.1V, CLK/SEL = OUT, VBATT = 2.4V,
includes load regulation error for 0A ≤ ILX ≤ 0.55A
3.17
3.30
3.38
V
FB Regulation Voltage
Adjustable output, CLK/SEL = OUT, VBATT = 2.4V,
includes load regulation error for 0A ≤ ILX ≤ 0.55A
1.210
1.24
1.255
V
FB Input Current
VFB = 1.25V
0.01
Output Voltage Adjust Range
2.5
Output Voltage Lockout
Threshold
(Note 4)
Load Regulation (Note 5)
CLK/SEL = OUT, No load to full load
2.0
2.15
20
nA
5.5
V
2.3
V
-1.6
%
MAX1700
0.1
20
MAX1701
3
20
Supply Current in Shutdown
V ONB = 3.6V
µA
Supply Current in Low-Power
Mode (Note 6)
CLK/SEL = GND (MAX1700)
35
70
CLK/SEL = GND (MAX1701)
55
110
Supply Current in Low-Noise
Mode (Note 6)
CLK/SEL = OUT (MAX1700)
125
250
CLK/SEL = OUT (MAX1701)
140
300
POUT Leakage Current
VLX = 0V, VOUT = 5.5V
0.1
20
µA
LX Leakage Current
VLX = V ONB = VOUT = 5.5V
0.1
20
µA
CLK/SEL = GND
0.2
0.45
CLK/SEL = OUT
0.13
0.28
0.25
0.5
µA
µA
DC-DC SWITCHES
Switch On-Resistance
N-channel
P-channel
N-Channel Current Limit
P-Channel Turn-Off Current
2
CLK/SEL = OUT
1100
1300
1600
CLK/SEL = GND
250
400
550
CLK/SEL = GND
20
_______________________________________________________________________________________
120
Ω
mA
mA
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
(CLK/SEL = ONA = ONB = FB = PGND = GND, OUT = POUT, VOUT = 3.6V (Note 6); MAX1701: AIN = LBN = GND, LBP = REF,
TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
1.25
1.263
V
30
nA
9
16
mmho
GAIN BLOCK (MAX1701)
AIN Reference Voltage
IAO = 20µA
1.237
AIN Input Current
VAIN = 1.5V
-30
Transconductance
10µA < IAO = 100µA
AO Output Low Voltage
VAIN = 0.7V, IAO = 100µA
0.1
0.4
V
AO Output High Leakage
VAIN = 1.5V, VAO = 5.5V
0.01
1
µA
5
POWER GOOD (MAX1701)
Internal Trip Level
Rising VOUT, VFB < 0.1V
2.93
2.97
3.02
V
External Trip Level
Rising VFB
1.1
1.12
1.14
V
POK Low Voltage
ISINK = 1mA, VOUT = 3.6V or ISINK = 20µA, VOUT = 1V
0.03
0.4
V
POK High Leakage Current
VOUT = VPOK = 5.5V
0.01
1
µA
±0.5
5
mV
1.5
V
LOW-BATTERY COMPARATOR
LBN, LBP Input Offset
LBP falling, 15mV hysteresis
-5
LBN, LBP Common Mode
Range
To maintain input offset < ±5mV (at least one input must
be within this range)
0.5
LBO Output Low Voltage
ISINK = 1mA, VOUT = 3.6V or ISINK = 20µA, VOUT = 1V
0.03
0.4
V
LBO High Leakage
VOUT = VLBO = 5V
0.01
1
µA
LBN, LBP Input Current
VLBP = VLBN = 1.5V
20
nA
1.250
1.263
V
5
15
mV
0.2
5
mV
REFERENCE
Reference Output Voltage
IREF = 0
REF Load Regulation
-1µA < IREF < 50µA
REF Supply Rejection
2.5V < VOUT < 5V
1.237
LOGIC AND CONTROL INPUTS
Input Low Voltage (Note 7)
1.2V < VOUT < 5.5V, ONA and ONB
0.2VOUT
2.5V < VOUT < 5.5V, CLK/SEL
0.2VOUT
Input High Voltage (Note 7)
Input High Voltage (Note 7)
1.2V < VOUT < 5.5V, ONA and ONB
0.8VOUT
2.5V < VOUT < 5.5V, CLK/SEL
0.8VOUT
Logic Input Current
ONA, ONB, and CLK/SEL
Internal Oscillator Frequency
CLK/SEL = OUT
V
V
1
µA
260
-1
300
340
kHz
Oscillator Maximum Duty Cycle
80
86
90
%
External Clock Frequency
Range
200
400
kHz
Minimum CLK/SEL Pulse Width
200
ns
Maximum CLK/SEL Rise/Fall
Time
100
ns
_______________________________________________________________________________________
3
MAX1700/MAX1701
ELECTRICAL CHARACTERISTICS (continued)
MAX1700/MAX1701
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
ELECTRICAL CHARACTERISTICS (continued)
(CLK/SEL = ONA = ONB = FB = PGND = GND, OUT = POUT, VOUT = 3.6V (Note 6); MAX1701: AIN = LBN = GND, LBP = REF,
TA = -40°C to +85°C, unless otherwise noted.) (Note 8)
PARAMETER
CONDITIONS
MIN
Output Voltage (Note 3)
VFB < 0.1V, CLK/SEL = OUT, VBATT = 2.4V, includes load
regulation error for 0A ≤ ILX ≤ 0.55A
FB Regulation Voltage
TYP
MAX
UNITS
3.17
3.38
V
Adjustable output, CLK/SEL = OUT, VBATT = 2.4V,
includes load regulation error for 0A ≤ ILX ≤ 0.55A
1.20
1.27
V
Output Voltage Lockout
Threshold
(Note 4)
2.0
2.3
V
Supply Current in Shutdown
V ONB = 3.6V
20
µA
Supply Current in Low-Power
Mode (Note 6)
CLK/SEL = GND (MAX1700)
70
CLK/SEL = GND (MAX1701)
110
Supply Current in Low-Noise
Mode (Note 6)
CLK/SEL = OUT (MAX1700)
250
CLK/SEL = OUT (MAX1701)
300
DC-DC CONVERTER
µA
µA
DC-DC SWITCHES
Switch On-Resistance
N-channel
CLK/SEL = GND
0.45
CLK/SEL = OUT
0.28
P-channel
Ω
0.5
CLK/SEL = OUT
1100
1800
CLK/SEL = GND
250
600
AIN Reference Voltage
IAO = 20µA
1.23
1.27
V
Transconductance
10µA < IAO < 100µA
5
16
mmho
N-Channel Current Limit
mA
GAIN BLOCK (MAX1701)
POWER-GOOD (MAX1701)
Internal Trip Level
Rising VOUT, VFB < 0.1V
2.92
3.03
V
External Trip Level
Rising VFB
1.1
1.14
V
LOW-BATTERY COMPARATOR (MAX1701)
LBN, LBP Input Offset
LBP falling, 15mV hysteresis
-5
5
mV
LBN, LBP Common Mode
Range
To maintain input offset < ±5mV (at least one input must
be within this range)
0.5
1.5
V
IREF = 0
1.23
1.27
V
REFERENCE
Reference Output Voltage
4
_______________________________________________________________________________________
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
(CLK/SEL = ONA = ONB = FB = PGND = GND, OUT = POUT, V OUT = 3.6V, MAX1701: AIN = LBN = GND, LBP = REF,
TA = -40°C to +85°C, unless otherwise noted.) (Note 8)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
LOGIC AND CONTROL INPUTS
Input Low Voltage (Note 7)
Input High Voltage (Note 7)
Input High Voltage (Note 7)
1.2V < VOUT < 5.5V, ONA and ONB
0.2VOUT
2.5V < VOUT < 5.5V, CLK/SEL
0.2VOUT
1.2V < VOUT < 5.5V, ONA and ONB
0.8VOUT
2.5V < VOUT < 5.5V, CLK/SEL
0.8VOUT
Logic Input Current
ONA, ONB, and CLK/SEL
Internal Oscillator Frequency
CLK/SEL = OUT
V
V
-1
1
µA
260
340
kHz
Oscillator Maximum Duty Cycle
80
92
%
External Clock Frequency
Range
200
400
kHz
Note 1: Operating voltage. Since the regulator is bootstrapped to the output, once started it will operate down to 0.7V input.
Note 2: Start-up is tested with the circuit of Figure 2.
Note 3: In low-power mode (CLK/SEL = GND), the output voltage regulates 1% higher than low-noise mode (CLK/SEL = OUT or
synchronized).
Note 4: The regulator is in start-up mode until this voltage is reached. Do not apply full load current.
Note 5: Load regulation is measured from no-load to full load where full load is determined by the N-channel switch current limit.
Note 6: Supply current from the 3.30V output is measured between the 3.30V output and the OUT pin. This current correlates
directly to the actual battery supply current, but is reduced in value according to the step-up ratio and efficiency. Set VOUT
= 3.6V to keep the internal switch open when measuring the current into the device.
Note 7: ONA and ONB have hysteresis of approximately 0.15xVOUT.
Note 8: Specifications to -40°C are guaranteed by design and not production tested.
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
60
VIN = 0.9V
VIN = 2.4V
80
70
VIN = 1.2V
60
50
50
PFM
PWM
40
PFM
PWM
0.1
1
10
100
LOAD CURRENT (mA)
1000
T = 25°C
5.0
4.0
T = 85°C
3.0
T = -40°C
2.0
1.0
30
40
6.0
MAX1770-03
90
SHUTDOWN CURRENT (µA)
VIN = 1.2V
70
VIN = 3.6V
EFFICIENCY (%)
EFFICIENCY (%)
80
7.0
MAX1700-02
VIN = 2.4V
90
100
MAX1700-01
100
MAX1701
SHUTDOWN CURRENT
vs. INPUT VOLTAGE (V)
EFFICIENCY vs. LOAD CURRENT
(VOUT = 5V)
EFFICIENCY vs. LOAD CURRENT
(VOUT = 3.3V)
0
0.1
1
10
100
LOAD CURRENT (mA)
1000
0
1
2
3
4
5
6
INPUT VOLTAGE (V)
_______________________________________________________________________________________
5
MAX1700/MAX1701
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
REFERENCE VOLTAGE
vs. REFERENCE CURRENT
FREQUENCY vs. TEMPERATURE
1.248
1.250
1.248
1.246
1.246
1.244
1.244
VOUT = 5V
315
FREQUENCY (kHz)
1.250
320
1.252
REFERENCE VOLTAGE (V)
1.252
325
MAX1700-05
1.254
MAX1700-04
1.254
MAX1700-06
REFERENCE VOLTAGE
vs. TEMPERATURE
REFERENCE VOLTAGE (V)
310
305
300
295
VOUT = 3.3V
290
285
-40
-20
0
20
40
60
80
100
280
0
10
TEMPERATURE (°C)
20
30
40
50
60
70
80
1.5
1.3
1.1
TA = -40°C
0.9
60
80 100 120 140
MAX1700-08
PWM
1.2
1.0
0.8
0.6
TA = +25°C
0.7
40
1.4
CURRENT LIMIT (A)
1.7
20
TEMPERATURE (°C)
1.6
MAX1700/01 TOC06a
NO-LOAD START-UP:
1.0V AT -40°C
0.79 AT +25°C
0.64V AT +85°C
CONSTANT-CURRENT LOAD
VOUT = 3.3V
L = 10µH
D1 = MBR0520L
1.9
0
PEAK INDUCTOR CURRENT
vs. OUTPUT VOLTAGE
2.3
2.1
-40 -20
REFERENCE CURRENT (µA)
START-UP INPUT VOLTAGE
vs. OUTPUT CURRENT
START-UP INPUT VOLTAGE (V)
MAX1700/MAX1701
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
0.4
PFM
TA = +85°C
0.5
0.2
0.01
0.1
1
10
1000
100
2.5
OUTPUT CURRENT (mA)
3
3.5
4
4.5
5
5.5
OUTPUT VOLTAGE (V)
HEAVY-LOAD SWITCHING WAVEFORMS
(VOUT = 3.3V)
LINE-TRANSIENT RESPONSE
MAX1700-08
MAX1700-09
VOUT
A
0V
A
B
0V
0A
B
C
1µs/div
6
5ms/div
VIN = 1.1V, IOUT = 200mA, VOUT = 3.3V
IOUT = 0mA, VOUT = 3.3V
A = LX VOLTAGE, 2V/div
B = INDUCTOR CURRENT, 0.5A/div
C = VOUT RIPPLE, 50mV/div, AC COUPLED
A = VIN, 1.1V TO 2.1V, 1V/div
B = VOUT RIPPLE, 50mV/div, AC COUPLED
_______________________________________________________________________________________
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
POWER-ON DELAY
(PFM MODE)
LOAD-TRANSIENT RESPONSE
MAX1700-10
MAX1700-11
3.3V
A
200mA
A
0A
B
C
B
0mA
5ms/div
2ms/div
A = VON1, 2V/div
B = VOUT, 1V/div
C = INPUT CURRENT, 0.2A/div
VIN = 1.1V, VOUT = 3.3V
A = LOAD CURRENT, 0mA TO 200mA, 0.2A/div
B = VOUT RIPPLE, 50mV/div, AC COUPLED
DECT LOAD-TRANSIENT RESPONSE
GSM LOAD-TRANSIENT RESPONSE
MAX1700-13
MAX1700-12
3.3V
5V
A
A
B
B
0A
0A
2ms/div
1ms/div
VIN = 3.6V, VOUT = 5V, COUT = 440µF
VIN = 1.2V, VOUT = 3.3V, COUT = 440µF
A = VOUT RIPPLE, 200mV/div, AC COUPLED
B = LOAD CURRENT, 100mA TO 1A, 0.5A/div,
PULSE WIDTH = 577µs
A = VOUT RIPPLE, 200mV/div, AC COUPLED
B = LOAD CURRENT, 50mA TO 400mA, 0.2A/div,
PULSE WIDTH = 416µs
NOISE SPECTRUM
(VOUT = 3.3V, VIN = 1.2V, RLOAD = 50Ω)
NOISE (mVRMS)
MAX1700-14
2.7
0
0.1k
1k
10k
FREQUENCY (Hz)
100k
1M
_______________________________________________________________________________________
7
MAX1700/MAX1701
Typical Operating Characteristics (continued)
(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
MAX1700/MAX1701
Pin Description
PIN
8
NAME
FUNCTION
MAX1700
MAX1701
—
1
LBP
Low-Battery Comparator Non-Inverting Input
—
2
LBN
Low-Battery Comparator Inverting Input
3
3
REF
Reference Output. Bypass with a 0.22µF capacitor to GND. REF can source up to
50µA.
Switching-Mode Selection and External-Clock Synchronization Inputs.
• CLK/SEL=Low: Low-power, delivers up to 10% of full load current.
• CLK/SEL=High: High-power PWM mode. Full output power available. Operates in
low-noise, constant-frequency mode.
• CLK/SEL=External Clock: High-power PWM mode with the internal oscillator
synchronized to the external clock.
Turning on with CLK/SEL=0V also serves as a soft-start function since peak inductor
current is limited to 25% of that allowed in PWM mode.
4
4
CLK/SEL
5
5
GND
Ground
—
6
POK
Power-Okay Comparator Output. Open drain N-channel output is low when VOUT is
10% below regulation point. No internal delay is provided.
7
7
ONB
Shutdown Input. When ONB =high and ONA=low, the IC is off and the load is connected to the battery through the Schottky diode.
Turn ON Input. When ONA=high or ONB =low, the IC turns on.
8
8
ONA
—
9
AO
Gain Block Output. This open-drain output sinks when VAIN <VREF.
—
10
AIN
Gain Block AIN input. When AIN is low, AO sinks current. The transconductance from
AIN to AO is 9mmhos.
11
11
FB
DC-DC Converter Dual-Mode Feedback Input. For a fixed output voltage of +3.3V,
connect FB to GND. For adjustable output, connect a divider between POUT and GND
to set the output voltage in the range of 2.5V to 5V.
12
12
PGND
13
13
LX
14
14
OUT
15
15
POUT
—
16
LBO
Low-Battery Comparator Output. Open-drain N-channel output is low when LBN > LBP
Input hysteresis is 15mV.
1, 2, 6, 9,
10, 16
—
I.C.
Internal Connection. Leave open or connect to GND.
Source of N-Channel Power MOSFET Switch. Connect to high-current ground path.
Drain of P-Channel Synchronous Rectifier and N-Channel Switch
Output Sense Input. Power source for the IC.
Source of P-Channel Synchronous Rectifier MOSFET Switch. Connect an external
Schottky diode from LX to POUT.
_______________________________________________________________________________________
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
MAX1700/MAX1701
UNDERVOLTAGE LOCKOUT
OUT
IC PWR
PFM/PWM
CONTROLLER
2.25V
START-UP
EN OSCILLATOR
Q
D
Q
POUT
PCH
0.25Ω
ONA
ON
ONB
REF
1.25V
RDY
OSCILLATOR
300kHz
FEEDBACK AND
POWER-GOOD
SELECT
FB
OSC
EN
REF
GND
CLK/SEL
LX
EN
REFERENCE
FEEDBACK
Q
PFM/PWM
NCH
0.13Ω
MODE
PGND
POK*
FB
N
AIN*
AO*
GAIN
BLOCK
N
REF
COMPARATOR
LBP*
LBO*
N
LBN*
*MAX1701 ONLY
Figure 1. Functional Diagram
_______________Detailed Description
The MAX1700/MAX1701 are highly efficient, low-noise
power supplies for portable RF and data acquisition
instruments. The MAX1700 combines a boost switching
regulator, N-channel power MOSFET, P-channel synchronous rectifier, precision reference, and shutdown
control. The MAX1701 contains all of the MAX1700 features plus a versatile gain amplifier, POK output, and a
low-battery comparator (Figure 1). The MAX1700/
MAX1701 come in a 16-pin QSOP package, which
occupies no more space than an 8-pin SO.
The switching DC-DC converter boosts a 1- to 3-cell
input to an adjustable output between 2.5V and 5.5V.
The MAX1700/MAX1701 start from a low 1.1V input and
remain operational down to 0.7V.
These devices are optimized for use in cellular phones
and other applications requiring low noise during full-
power operation, as well as low-quiescent current for
maximum battery life during standby and shutdown
modes. They feature constant-frequency (300kHz), lownoise PWM operation with up to 800mA output capability. See Table 1 for typical available output current. A
low-quiescent-current, low-power mode offers an output up to 100mA and reduces quiescent power consumption to 200µW. In shutdown mode, the quiescent
current is further reduced to just 3µA. Figure 2 shows
the standard application circuit for the
MAX1700/MAX1701.
Additional features include synchronous rectification for
high efficiency and improved battery life, a POK output,
and an uncommitted comparator for low-battery detection (MAX1701). A CLK input allows frequency synchronization to reduce interference. Dual shutdown controls
allow shutdown using a momentary pushbutton switch
and microprocessor control (MAX1701).
_______________________________________________________________________________________
9
MAX1700/MAX1701
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
0.7V TO 5.5V
POUT
22µF
L1
10µH
REF
MBR0520L
MAX1700
MAX1701
OUT
CLK/SEL
P
FB
OUTPUT
LX
R
LX
Q
D1
2x
100µF
POUT
10Ω
ONA
S
N
0.22µF
OUT
ONB
0.22µF
R1
REF
GND
0.22µF
FB
PGND
ADJUSTABLE
FIXED
OUTPUT
(GND)
R2
1.3A CURRENT
LIMIT
PGND
OSC
Figure 2. Fixed or Adjustable Output (PWM mode).
Figure 3. Simplified PWM Controller Block Diagram
Table 1. Typical Available Output Current
the output filter capacitor and load. As the energy
stored in the inductor is depleted, the current ramps
down and the output diode and synchronous rectifier
turn off. Voltage across the load is regulated using
either low-noise PWM or low-power operation, depending on the CLK/SEL pin setting (Table 2).
NUMBER
OF CELLS
INPUT
OUTPUT
OUTPUT
VOLTAGE (V) VOLTAGE (V) CURRENT (mA)
1 NiCd/NiMH
1.2
3.3
300
2 NiCd/NiMH
2.4
3.3
750
2 NiCd/NiMH
2.4
5.0
525
3 NiCd/NiMH
or 1 Li-Ion
3.6
5.0
850
Table 2. Selecting the Operating Mode
CLK/SEL
MODE
FEATURES
0
Low Power
Low supply current
1
PWM
Low noise,
high output current
External Clock
(200kHz to 400kHz)
Synchronized
PWM
Low noise,
high output current
Step-Up Converter
The step-up switching DC-DC converter generates an
adjustable output from 2.5V to 5.5V. During the first part
of each cycle, the internal N-channel MOSFET switch is
turned on. This allows current to ramp up in the inductor and store energy in a magnetic field. During the
second part of each cycle, when the MOSFET is turned
off, the voltage across the inductor reverses and forces
current through the diode and synchronous rectifier to
10
Low-Noise PWM Operation
When CLK/SEL is pulled high, the MAX1700/MAX1701
operate in a higher power, low-noise pulse-widthmodulation (PWM) mode. During PWM operation, they
switch at a constant frequency (300kHz) and then modulate the MOSFET switch pulse width to control the
power transferred per cycle and regulate the voltage
across the load. In PWM mode the devices can output
up to 800mA. Switching harmonics generated by fixedfrequency operation are consistent and easily filtered.
See the Noise Spectrum Plot in the Typical Operating
Characteristics.
During PWM operation, each rising edge of the internal
clock sets a flip-flop, which turns on the N-channel
MOSFET switch (Figure 3). The switch is turned off
when the sum of the voltage-error, slope compensation,
and current-feedback signals trips a multi-input comparator and resets the flip-flop; the switch remains off
for the rest of the cycle. When a change occurs in the
output-voltage error signal into the comparator, it shifts
the level to which the inductor current is allowed to
ramp during each cycle and modulates the MOSFET
switch pulse width. A second comparator enforces an
inductor current limit of 1.6A max.
______________________________________________________________________________________
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
POUT
Q
R
P
ERROR
COMPARATOR
FB
LX
S
Q
N
REF
R
400mA
CURRENT
LIMIT
Synchronous Rectifier
The MAX1700/MAX1701 feature an internal 250mΩ, Pchannel synchronous rectifier to enhance efficiency.
Synchronous rectification provides a 5% efficiency
improvement over similar nonsynchronous boost regulators. In PWM mode, the synchronous rectifier is
turned on during the second half of each switching
cycle. In low-power mode, an internal comparator turns
on the synchronous rectifier when the voltage at LX
exceeds the boost-regulator output and then turns it off
when the inductor current drops below 70mA.
Low-Voltage Start-Up Oscillator
PGND
Figure 4. Controller Block Diagram in Low-Power PFM Mode
Synchronized PWM Operation
By applying an external clock to CLK/SEL, the
MAX1700/MAX1701 can also be synchronized in PWM
mode to a frequency between 200kHz and 400kHz.
This allows the user to set the harmonics to avoid IF
bands in wireless applications. The synchronous rectifier is also active during synchronized PWM operation.
Low-Power PFM Operation
Pulling CLK/SEL low places the MAX1700/MAX1701 in
a low-power mode. During low-power mode, PFM operation regulates the output voltage by transferring a
fixed amount of energy during each cycle and then
modulating the switching frequency to control the
power delivered to the output. The devices switch only
as needed to service the load, resulting in the highest
possible efficiency at light loads. Output current capability in PFM mode is 100mA. The output voltage is typically 1% higher than the output voltage in PWM mode.
During PFM operation, the error comparator detects the
output voltage falling out of regulation and sets a flipflop, turning on the N-channel MOSFET switch (Figure
4). When the inductor current ramps to the PFM mode
current limit (400mA typical) and stores a fixed amount
of energy, the current-sense comparator resets a flipflop. The flip-flop turns off the N-channel switch and
turns on the P-channel synchronous rectifier. A second
flip-flop, previously reset by the switch’s “on” signal,
inhibits the error comparator from initiating another
cycle until the energy stored in the inductor is transferred to the output filter capacitor and the synchronous
The MAX1700/MAX1701 use a CMOS, low-voltage
start-up oscillator for a 1.1V guaranteed minimum startup input voltage at +25°C. On start-up, the low-voltage
oscillator switches the N-channel MOSFET until the output voltage reaches 2.15V. Above this level, the normal
boost-converter feedback and control circuitry take
over. Once the device is in regulation, it can operate
down to a 0.7V input since internal power for the IC is
bootstrapped from the output using the OUT pin. Do
not apply full load until the output exceeds 2.4V.
Table 3. On/Off Logic Control
ONA
ONB
Status
0
0
On
0
1
Off
1
0
On
1
1
On
Shutdown
The MAX1700/MAX1701 shut down to reduce quiescent current to typically 3µA. During shutdown, the reference, low-battery comparator, gain block, and all
feedback and control circuitry are off. The boost converter’s output drops to one Schottky diode drop below
the input.
Table 3 shows the control logic with ONA and ONB.
Both inputs have trip points near 0.5V OUT with
0.15VOUT hysteresis.
Low-Battery Comparator (MAX1701)
The internal low-battery comparator has uncommitted
inputs and an open-drain output (LBO) capable of sinking 1mA. To use it as a low-battery-detection comparator, connect the LBN input to the reference, and
connect the LBP input to an external resistor divider
______________________________________________________________________________________
11
MAX1700/MAX1701
rectifier current has ramped down to 70mA. This forces
operation with a discontinuous inductor current.
LOGIC HIGH
D
Q
MAX1700/MAX1701
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
0.7V TO 5.5V
POUT
REF
L1
MAX1701
D1
MAX1701
LBO
POUT
LBN
CLK/SEL
10Ω
ONA
ONB
0.22µF
R3
POK
LBP
R4
LBO
LBN
REF
AO
GND PGND FB AIN
10k
R6
LBP
OUT
ARBITRARY
VOLTAGE
VOLTAGE MONITOR
LOW-BATTERY MONITOR
0.22µF
R5
LX
GND
BATTERY
VOLTAGE
R5
ARBITRARY VOLTAGE MONITOR
Figure 7. Detecting Battery Voltages Below 1.25V (MAX1701)
R6
OUTPUT
10Ω
P
Figure 5. Detecting Battery Voltage Above 1.25V
C5
270k
C3
0.22µF
POUT
OUT
R3
LBN
C4
POUT
OUT
MAX1701
R4
LBO
MAX1701
LBO
R3
LBP
0.22µF
LBN
GND
Figure 6. Using the Low-Battery Comparator to Sense the
Output Voltage (MAX1701)
between the positive battery terminal and GND (Figure
5). The resistor values are then calculated as follows:
R3 = R4(VTH/VLBN -1)
where VTH is the desired input voltage trip threshold
and VLBN = VREF = 1.25V. Since the input bias current
into LBP is less than 20nA, R4 can be a large value
(such as 270kΩ or less) without sacrificing accuracy.
The inputs have a common-mode input range from
0.5V to 1.5V and an input-referred hysteresis of 15mV.
The low-battery comparator can also be used to monitor the output voltage, as shown in Figure 6.
To set the low-battery threshold to a voltage below the
1.25V reference, insert a resistor divider between REF
12
GND
R4
REF
0.22µF
LBP
REF
Figure 8. Using the Low-Battery Comparator for Load Control
During Start-Up
and LBN and connect the battery to the LBP input
through a 10kΩ current-limiting resistor (Figure 7). The
equation for setting the resistors for the low-battery
threshold is then as follows:
R5 = R6(VREF/VLBP -1)
where VLBP is the desired voltage threshold. In Figures
5, 6, and 7, LBO goes low for a low-voltage input. The
low-battery comparator can be used to check the output voltage or to control the load directly on POUT during start-up (Figure 8). Use the following equation to set
the resistor values:
R3 = R4(VOUTTH/VLBP - 1)
where VOUTTH is the desired output-voltage trip point
and VLBP is connected to the reference or 1.25V.
______________________________________________________________________________________
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
Gain Block (MAX1701)
The MAX1701’s gain block can function as a third comparator or can be used to build a linear regulator using
an external P-channel MOSFET pass device. The gainblock output is a single-stage transconductance amplifier that drives an open-drain N-channel MOSFET.
Figure 9 shows the gain block used in a linear regulator. The output of an external P-channel pass element is
compared to the internal reference. The difference is
amplified and used to drive the gate of the pass element. Use a logic-level PFET such as the Fairchild
). If the PFET RDS(ON) is
NDS336P (RDS(ON) = 270mΩ
less than 250mΩ, the linear regulator output filter
capacitance may need to be increased to above 47µF.
Power-OK (MAX1701)
The MAX1701 features a power-good comparator. This
comparator’s open-drain output (POK) is pulled low
when the output voltage falls to 10% below the regulation point.
IN
20k
2x
100µF
MAX1701
__________________Design Procedure
P
LX
47µF
AO
N
Setting the Output Voltages
Set the output voltage between 2.5V and 5.5V by connecting a resistor voltage-divider to FB from OUT to
GND, as shown in Figure 2. The resistor values are then
as follows:
R1 = R2 (VOUT/VFB - 1)
R5
AIN
where VFB, the boost-regulator feedback setpoint, is
1.23V. Since the input bias current into FB is less than
20nA, R2 can have a large value (such as 270kΩ or
less) without sacrificing accuracy. Connect the resistor
voltage-divider as close to the IC as possible, within
0.2in. (5mm) of the FB pin.
REF
R6
Figure 9. Using Gain Block as a Linear Regulator
Table 4. Component Suppliers
SUPPLIER
PHONE
Inductor Selection
FAX
AVX
USA: (803) 946-0690
(800) 282-4975
(803) 626-3123
Coilcraft
USA: (847) 639-6400
(847) 639-1469
Matsuo
USA: (714) 969-2491
(714) 960-6492
Motorola
USA: (602) 303-5454
(602) 994-6430
Sanyo
USA: (619) 661-6835
Japan: 81-7-2070-6306
(619) 661-1055
81-7-2070-1174
Sumida
USA: (847) 956-0666
Japan: 81-3-3607-5111
(847) 956-0702
81-3-3607-5144
The MAX1700/MAX1701’s high switching frequency
allows the use of a small surface-mount inductor. A
10µH inductor should have a saturation-current rating
that exceeds the N-channel switch current limit of 1.6A.
However, it is generally acceptable to bias the inductor
current into saturation by as much as 20%, although
this will slightly reduce efficiency. For high efficiency,
choose an inductor with a high-frequency core material
(such as ferrite) to reduce core losses. To minimize
radiated noise, use a toroid, pot core, or shielded bobbin inductor. Connect the inductor from the battery to
the LX pin as close to the IC as possible. See Table 4
for a list of component suppliers and Table 5 for suggested components.
Table 5. Component Selection Guide
PRODUCTION
INDUCTORS
CAPACITORS
DIODES
Surface Mount
Sumida CDR63B, CD73, CDR73B, CD74B series
Coilcraft DO1608, DO3308, DT3316 series
Matsuo 267 series
Sprague 595D series
AVX TPS series
Motorola MBR0520L
Through Hole
Sumida RCH654 series
Sanyo OS-CON series
Nichicon PL series
1N5817
______________________________________________________________________________________
13
MAX1700/MAX1701
Reference
The MAX1700/MAX1701 have an internal 1.250V, 1%
bandgap reference. Connect a 0.22µF bypass capacitor to GND within 0.2in. (5mm) of the REF pin. REF can
source up to 50µA of external load current.
MAX1700/MAX1701
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
µC
270k
LX
MAX1701
ONB
ON/OFF
VDD
OUT
I/O
ONA
0.1µF
POUT
MAX1700
I/O
MAX8865/MAX8866 DUAL OR
MAX8863/MAX8864 SINGLE
LOW-DROPOUT LINEAR REGULATORS
PA
270k
µC
Figure 10. Momentary Pushbutton On/Off Switch
Output Diode
Use a Schottky diode, such as a 1N5817, MBR0520L, or
equivalent. The Schottky diode carries current during
start-up, and in PFM mode after the synchronous rectifier
turns off. Thus, its current rating only needs to be 500mA.
Connect the diode between LX and POUT as close to the
IC as possible. Do not use ordinary rectifier diodes since
slow switching speeds and long reverse recovery times
will compromise efficiency and load regulation.
Input and Output Filter Capacitors
Choose input and output filter capacitors that will service the input and output peak currents with acceptable voltage ripple. Choose input capacitors with
working voltage ratings over the maximum input voltage, and output capacitors with working voltage ratings
higher than the output.
For full output, two 100µF, 100mΩ, low-ESR tantalum output filter capacitors are recommended. For loads below
250mA, a single 100µF output capacitor will suffice. The
input filter capacitor (CIN) reduces peak currents drawn
from the input source and reduces input switching noise.
The input voltage source impedance determines the
required size of the input capacitor. When operating
directly from one or two NiCd cells placed close to the
MAX1700/MAX1701, use a 22µF, low-ESR input filter
capacitor. When operating from a power source placed
farther away, or from higher impedance batteries such as
alkaline or lithium cells, use one or two 100µF, 100mΩ,
low-ESR tantalum capacitors.
Sanyo OS-CON and Panasonic SP/CB-series ceramic
capacitors offer the lowest ESR. Low-ESR tantalum
capacitors are a good choice and generally offer a
good tradeoff between price and performance. Do not
14
RADIO
Figure 11. Typical Phone Application
exceed the ripple current ratings of tantalum capacitors. Avoid most aluminum-electrolytic capacitors,
since their ESR is often too high.
Bypass Capacitors
Two ceramic bypass capacitors are required for proper
operation. Bypass REF with a 0.22µF capacitor to GND.
Also connect a 0.22µF ceramic capacitor from OUT to
GND. Each should be placed as close to their respective pins as possible, within 0.2in. (5mm) of the DC-DC
converter IC. See Table 4 for suggested suppliers.
__________Applications Information
Push-On/Push-Off Control
A momentary pushbutton switch can be used to turn
the MAX1700/MAX1701 on and off. In Figure 10, ONA
is pulled low and ONB is pulled high when the part is
off. When the momentary switch is pressed, ONB is
pulled low and the regulator turns on. The switch must
be pressed long enough for the microcontroller to exit
reset (200ms) and drive ONA high. A small capacitor is
added to help debounce the switch. The controller
issues a logic high to ONA, which holds the part on
regardless of the switch state. To turn the regulator off,
press the switch again, allowing the controller to read
the switch status and pull ONA low. When the switch is
released, ONB is pulled high.
Use in a Typical Wireless
Phone Application
The MAX1700/MAX1701 are ideal for use in digital
cordless and PCS phones. The power amplifier (PA) is
connected directly to the boost-converter output for
maximum voltage swing (Figure 11). Low-dropout linear
regulators are used for post-regulation to generate
______________________________________________________________________________________
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
Designing a PC Board
High switching frequencies and large peak currents
make PC board layout an important part of design.
Poor design can cause excessive EMI and groundbounce, both of which can cause instability or regulation errors by corrupting the voltage and current
feedback signals.
Power components (such as the inductor, converter IC,
filter capacitors, and output diode) should be placed as
close together as possible, and their traces should be
kept short, direct, and wide. A separate low-noise
ground plane containing the reference and signal
grounds should only connect to the power-ground
plane at one point. This minimizes the effect of powerground currents on the part. Consult the MAX1701 EV
kit manual for a layout example.
On multilayer boards, do not connect the ground pins
of the power components using vias through an internal
ground plane. Instead, place them close together and
route them in a star-ground configuration using component-side copper. Then use vias to connect the star
ground to the internal ground plane.
Keep the voltage feedback network very close to the
IC, within 0.2in. (5mm) of the FB pins. Keep noisy
traces, such as from the LX pin, away from the voltage
feedback networks. Separate them with grounded
copper. Consult the MAX1700 evaluation kit for a full
PC board example.
Soft-Start
To implement soft-start, set CLK/SEL low on power-up;
this forces low-power operation and reduces the peak
switching current to 550mA max. Once the circuit is in
regulation and start-up transients have settled,
CLK/SEL can be set high for full-power operation.
Intermittent Supply/Battery Connections
When boosting an input supply connected with a
mechanical switch, or a battery connected with spring
contacts, input power may sometimes be intermittent
as a result of contact bounce. When operating in PFM
mode with input voltages greater than 2.5V, restarting
after such dropouts may initiate high current pulses that
interfere with the MAX1700/MAX1701 internal MOSFET
switch control. If contact or switch bounce is anticipated in the design, use one of the following solutions.
1) Connect a capacitor (CONB) from ONB to VIN, a 1MΩ
resistor (RONB) from ONB to GND, and tie ONA to GND
(Figure 12). This RC network differentiates fast input
edges at VIN and momentarily holds the IC off until VIN
settles. The appropriate value of CONB is 10-5 times the
total output filter capacitance (COUT), so a COUT of
200µF results in CONB = 2nF.
2) Use the system microcontroller to hold the
MAX1700/MAX1701 in shut down from the time when
power is applied (or reapplied) until the output capacitance (COUT) has charged to at least the input voltage.
Power-on reset times of tens of milliseconds accomplish this.
3) Ensure that the IC operates, or at least powers up, in
PWM mode (CLK/SEL = high). Activate PFM mode only
after the VOUT has settled and all of the system’s poweron reset flags are cleared.
Pin Configurations (continued)
TOP VIEW
LBP 1
16 LBO
LBN 2
15 POUT
REF 3
14 OUT
CLK/SEL 4
MAX1701
13 LX
GND 5
12 PGND
POK 6
11 FB
ONB 7
10 AIN
ONA 8
9
QSOP
CONB
2nF
LX
7
ONB
RONB
1M
OUT
MAX1700
MAX1701
8
ONA
POUT
13
14
COUT
200µF
15
AO
Figure 12. Connecting CONB and RONB when Switch or
Battery-Contact Bounce Is Anticipated
______________________________________________________________________________________
15
MAX1700/MAX1701
low-noise power for DSP, control, and RF circuitry.
Typically, RF phones spend most of their life in standby
mode with only short periods in transmit/receive mode.
During standby, maximize battery life by setting
CLK/SEL = 0; this places the IC in low-power mode (for
the lowest quiescent power consumption).
Chip Information
TRANSISTOR COUNT: 531
SUBSTRATE CONNECTED TO GND
________________________________________________________Package Information
QSOP.EPS
MAX1700/MAX1701
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
16
______________________________________________________________________________________
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