MAX16945

MAX16945
19-4241; Rev 0; 8/08
30mA Inverting Charge Pump in SOT23
for EMI-Sensitive Automotive Applications
The MAX16945 ultra-small, monolithic, CMOS chargepump voltage inverter accepts an input voltage ranging
from +1.4V to +5.5V. This device features an ultra-low
12Ω output resistance, permitting loads of up to 30mA
at +105°C with maximum efficiency. The MAX16945
operates at a frequency of 125kHz, allowing use of
small external components. Its small external components, micropower shutdown mode, and wide temperature range make this device ideal for both automotive
and industrial applications.
Oscillator control circuitry and four power MOSFET
switches are included on-chip. The MAX16945 comes
in a 6-pin SOT23 package and operates over -40°C
to +105°C.
Features
♦ +1.4V to +5.5V Input Voltage Range
♦ 30mA Guaranteed Output Current at +105°C
♦ Slew-Rate Limited to Reduce EMI
♦ 0.1µA Logic-Controlled Shutdown
♦ Low 12Ω Output Resistance
♦ Startup Current Limited
♦ 6-Pin SOT23 Package
Ordering Information
Applications
Automotive and Industrial Equipment
PART
TEMP RANGE
PIN-PACKAGE
Small LCD Panels
MAX16945TGUT#
-40°C to +105°C
6 SOT23
Negative Supply from +5V or +3.3V Logic
Supplies
#Denotes a RoHS-compliant device that may include lead that
is exempt under RoHS requirements.
GaAsFET Bias Supplies
Note: The MAX16945 requires a special solder temperature
profile described in the Absolute Maximum Ratings section.
Handy-Terminals, PDAs
Pin Configuration
Typical Operating Circuit
1μF
TOP VIEW
INPUT
1.5V TO 5.5V
C1+
C1OUT
IN
MAX16945
SHDN
ON
OFF
NEGATIVE
OUTPUT
-1 ✕ VIN
60mA
OUT
1
IN
2
C1-
3
MAX16945
6
C1+
5
SHDN
4
GND
1μF
GND
SOT23
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1
MAX16945
General Description
MAX16945
30mA Inverting Charge Pump in SOT23
for EMI-Sensitive Automotive Applications
ABSOLUTE MAXIMUM RATINGS
IN to GND .................................................................-0.3V to +6V
C1+, SHDN to GND .......................................0.3V to (VIN +0.3V)
C1- to GND...............................................(VOUT - 0.3V) to +0.3V
OUT to GND .............................................................+0.3V to -6V
OUT Output Current............................................................90mA
OUT Short Circuit to GND..............................................Indefinite
Continuous Power Dissipation (TA = +70°C)
6-Pin SOT23 (derate 7.4mW/°C above +70°C) (Note 1) .....595mW
Junction-to-Case Thermal Resistance (θJC) (Note 1)
6-Pin SOT23 ................................................................39°C/W
Junction-to-Ambient Thermal Resistance (θJA) (Note 1)
6-Pin SOT23 ..............................................................134°C/W
Operating Temperature Range .........................-40°C to +105°C
Junction Temperature. .....................................................+150°C
Storage Temperature Range ............................-65°C to +150°C
Lead Temperature.......................................................... (Note 2)
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
Note 2: This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device
can be exposed to during board-level solder attach and rework. Maxim recommends the use of the solder profiles recommended in the industry-standard specification, JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and Convection reflow
processes. Preheating, per this standard, is required. Hand or wave soldering is not recommended.
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
(Circuit of Figure 1, C1 = C2 =2.2µF, VIN = VSHDN = +5V, VGND = 0, TA = 0°C to +105°C, unless otherwise noted. Typical values are
at TA = +25°C.)
PARAMETER
CONDITIONS
Supply Voltage Range
RL = 5kΩ
Quiescent Supply Current
TA = +25°C (Note 3)
Shutdown Supply Current
VSHDN = 0
MIN
TYP
1.4
5.5
TA = 0°C to +105°C
1.5
5.5
950
1700
TA = +25°C
0.002
1
TA = 0°C to +105°C
0.03
Short-Circuit Current
Output shorted to ground, TA = +25°C
Oscillator Frequency
TA = +25°C
70
125
Voltage Conversion Efficiency
IOUT = 0, TA = +25°C
99
99.9
Output Resistance
IOUT = 30mA (Note 4)
OUT-to-GND Shutdown Resistance
VSHDN = 0, OUT is internally pulled to GND
in shutdown
SHDN
Input Logic-High
SHDN
Input Logic-Low
SHDN
Bias Current
Wake-Up Time from Shutdown
2
MAX
TA = +25°C
170
TA = +25°C
12
TA = 0°C to +105°C
2.5V ≤ VIN ≤ 5.5V
25
8.5
2.5V ≤ VIN ≤ 5.5V
0.6
0.2
= GND or IN
IOUT = 15mA
TA = +25°C
TA = 0°C to +105°C
-100
µA
kHz
Ω
Ω
V
VIN - 0.2
VIN(MIN) ≤ VIN ≤ 2.5V
SHDN
µA
%
2.0
VIN(MIN) ≤ VIN ≤ 2.5V
V
mA
180
36
3
UNITS
+0.05
10
100
_______________________________________________________________________________________
+100
V
nA
µs
30mA Inverting Charge Pump in SOT23
for EMI-Sensitive Automotive Applications
(Circuit of Figure 1, C1 = C2 =2.2µF, VIN = VSHDN = +5V, VGND = 0, TA = 0°C to +105°C, unless otherwise noted. Typical values are
at TA = +25°C.)
PARAMETER
CONDITIONS
Supply Voltage Range
MIN
RL = 5kΩ
TYP
MAX
UNITS
5.5
V
1.6
Output Current
Continuous, long-term
Quiescent Supply Current
(Note 3)
Oscillator Frequency
µA
200
kHz
IOUT = 30mA (Note 5)
36
Ω
OUT-to-GND Shutdown Resistance
VSHDN = 0, OUT is internally pulled to GND
in shutdown
8.5
Ω
Input Logic-High
SHDN
Input Logic-Low
2.5V ≤ VIN ≤ 5.5V
125
mARMS
Output Resistance
SHDN
60
60
1800
2.1
VIN(MIN) ≤ VIN ≤ 2.5V
V
VIN - 0.2
2.5V ≤ VIN ≤ 5.5V
0.6
VIN(MIN) ≤ VIN ≤ 2.5V
0.2
V
Note 3: The MAX16945 may draw high supply current during startup, up to the minimum operating supply voltage. To guarantee
proper startup, the input supply must be capable of delivering 90mA more than the maximum load current.
Note 4: Output resistance is guaranteed with capacitor ESR of 0.3Ω or less.
Note 5: All specifications from -40°C to +105°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, C1 = C2 = 2.2µF, VIN = VSHDN = +5V, VGND = 0, TA = +25°C, unless otherwise noted.)
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
80
EFFICIENCY (%)
VIN = +2V
-1.5
-2.0
-2.5
VIN = +3.3V
-3.0
VIN = +3.3V
70
60
VIN = +2V
50
40
30
-3.5
-4.0
25
20
15
10
0
0
10
30
5
10
-5.0
0
35
20
VIN = +5V
-4.5
MAX16945 toc03
90
40
OUTPUT IMPEDANCE (Ω)
-1.0
VIN = +5V
MAX16945 toc02
-0.5
OUTPUT VOLTAGE (V)
100
MAX16945 toc01
0
OUTPUT IMPEDANCE
vs. INPUT VOLTAGE
EFFICIENCY vs. OUTPUT CURRENT
5.0
5.5
_______________________________________________________________________________________
3
20
30
OUTPUT CURRENT (mA)
40
50
0
10
20
30
OUTPUT CURRENT (mA)
40
50
1.5
2.0
2.5
3.0
3.5
4.0
4.5
INPUT VOLTAGE (V)
MAX16945
ELECTRICAL CHARACTERISTICS
Typical Operating Characteristics (continued)
(Circuit of Figure 1, C1 = C2 = 2.2µF, VIN = VSHDN = +5V, VGND = 0, TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
1.0
500
VIN = +5V
400
VIN = +3.3V
300
VIN = +2V
200
0.5
100
0
MAX16945 toc06
600
35
OUTPUT IMPEDANCE (Ω)
1.5
40
MAX16945 toc05
700
SUPPLY CURRENT (nA)
2.0
OUTPUT IMPEDANCE
vs. TEMPERATURE
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX16945 toc04
2.5
SUPPLY CURRENT (mA)
30
VIN = +2V
25
20
VIN = +3.3V
15
VIN = +5V
10
5
0
0
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
-40 -25 -10 5 20 35 50 65 80 95 110 125
-40 -25 -10 5 20 35 50 65 80 95 110 125
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
PUMP FREQUENCY
vs. TEMPERATURE
OUTPUT NOISE AND RIPPLE
MAX16945 toc08
MAX16945 toc07
120
119
PUMP FREQUENCY (kHz)
MAX16945
30mA Inverting Charge Pump in SOT23
for EMI-Sensitive Automotive Applications
118
117
116
10mV/div
115
114
113
112
111
110
2μs/div
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
STARTUP FROM SHUTDOWN
MAX16945 toc09
SHDN
5V/div
VOUT
2V/div
40μs/div
4
_______________________________________________________________________________________
30mA Inverting Charge Pump in SOT23
for EMI-Sensitive Automotive Applications
(Circuit of Figure 1, C1 = C2 = 2.2µF, VIN = VSHDN = +5V, VGND = 0, TA = +25°C, unless otherwise noted.)
OUTPUT RIPPLE
vs. CAPACITANCE
OUTPUT CURRENT
vs. CAPACITANCE
40
VIN = +4.375V, VOUT = -4V
30
MAX16945 toc11
200
OUTPUT RIPPLE (mV)
50
OUTPUT CURRENT (mA)
250
MAX16945 toc10
60
VIN = +2.825V, VOUT = -2.5V
20
VIN = +1.7V, VOUT = -1.5V
VIN = +4.375V, VOUT = -4V
150
VIN = +2.825V, VOUT = -2.5V
100
VIN = +1.7V, VOUT = -1.5V
50
10
0
0
0
1
2
3
4
5
6
7
8
9
0
10
1
2
3
Pin Description
PIN
NAME
1
OUT
2
IN
FUNCTION
Inverting Charge-Pump Output
Power-Supply Voltage Input. Input range
is 1.4V to 5.5V.
3
C1-
4
GND
Ground
SHDN
Shutdown Input. Drive SHDN high for
normal operation; drive SHDN low for
shutdown mode. OUT is actively pulled to
ground during shutdown.
5
6
C1+
Negative Terminal of the Flying Capacitor
Positive Terminal of the Flying Capacitor
4
5
6
7
8
9
10
CAPACITANCE (μF)
CAPACITANCE (μF)
C1
INPUT
1.5V TO 5.5V
2
3
C1-
6
C1+
IN
OUT
C3
RL
MAX16945
ON
OFF
5
SHDN
NEGATIVE
OUTPUT
-1 ✕ VIN
1
C2
GND
4
Figure 1. Typical Application Circuit
S1
S2
IN
C1
Detailed Description
The MAX16945 capacitive charge pump inverts the
voltage applied to its input. For highest performance,
use low-ESR capacitors.
During the first half-cycle, switches S2 and S4 open,
switches S1 and S3 close, and capacitor C1 charges to
the voltage at IN (Figure 2). During the second halfcycle, S1 and S3 open, S2 and S4 close, and C1 is
level shifted downward by VIN volts. This connects C1
in parallel with the reservoir capacitor C2. If the voltage
across C2 is smaller than the voltage across C1,
charge flows from C1 to C2 until the voltage across C2
reaches -VIN. The absolute value of the inverting output
S3
S4
C2
VOUT = -(VIN)
Figure 2. Ideal Voltage Inverter
voltage is always smaller than the value of the input
voltage due to the losses of the flying capacitor C1 and
the resistance of the switches S1–S4.
_______________________________________________________________________________________
5
MAX16945
Typical Operating Characteristics (continued)
MAX16945
30mA Inverting Charge Pump in SOT23
for EMI-Sensitive Automotive Applications
Efficiency Considerations
Shutdown
The efficiency of the MAX16945 is dominated by its quiescent supply current (IQ) at low output current, and by
its output impedance (ROUT) at higher output current.
Efficiency is calculated as follows:
The MAX16945 has a logic-controlled shutdown input.
Driving SHDN low places the device in a low-power
shutdown mode. The charge-pump switching halts,
supply current is reduced to 2nA, and OUT is actively
pulled to ground through a 3Ω resistance.
Driving SHDN high will restart the charge pump. The
switching frequency and capacitor values determine
how soon the device will reach 90% of the input voltage.
η≅
⎛ I
⎞
OUT x ROUT
⎜1 −
⎟
VIN
IOUT + IQ ⎝
⎠
IOUT
where the output impedance is roughly approximated by:
1
ROUT ≅
+ 2RSW + 4ESRC1 + ESRC2
fOSC x C1
(
)
The first term is the effective resistance of an ideal
switched-capacitor circuit (Figures 3a and 3b), and
RSW is the sum of the charge pump’s internal switch
resistances (typically 4Ω to 5Ω at VIN = +5V). The typical output impedance is more accurately determined
from the Typical Operating Characteristics.
fOSC
V+
VOUT
C2
C1
RL
Figure 3a. Switched-Capacitor Model
V+
VOUT
1
fOSC ✕ C1
C2
RL
Figure 3b. Equivalent Circuit
Current Limit
The MAX16945 limits its input current upon startup to
170mA (typ). This prevents low-current or higher output
impedance input supplies (such as alkaline cells) from
being overloaded when power is applied or when the
device awakes from shutdown.
6
Capacitor Selection
The charge-pump output resistance is a function of the
ESR of C1 and C2. To maintain the lowest output resistance, use capacitors with low ESR.
Flying Capacitor (C1)
Increasing the flying capacitor’s value reduces the output resistance. Above a certain point, increasing C1’s
capacitance has negligible effect because the output
resistance is then dominated by internal switch resistance and capacitor ESR.
Output Capacitor (C2)
Increasing the output capacitor’s value reduces the
output ripple voltage. Decreasing its ESR reduces both
output resistance and ripple. Lower capacitance values
can be used with light loads if higher output ripple can
be tolerated. Use the following equation to calculate the
peak-to-peak ripple:
VRIPPLE =
REQUIV
REQUIV =
Applications Information
IOUT
+ 2 × IOUT × ESRC2
2(fOSC )C2
Input Bypass Capacitor (C3)
If necessary, bypass the incoming supply to reduce its
AC impedance and the impact of the MAX16945’s
switching noise. An input bypass capacitor (C3) with a
value equal to that of C1 is recommended.
Voltage Inverter
The most common application for these devices is a
charge-pump voltage inverter (Figure 1). This application requires only two external components, capacitors
C1 and C2, plus an input bypass capacitor C3, if necessary. See the Capacitor Selection section for suggested capacitor sizes.
_______________________________________________________________________________________
30mA Inverting Charge Pump in SOT23
for EMI-Sensitive Automotive Applications
Combined Doubler/Inverter
In the circuit of Figure 6, capacitors C1 and C2 form the
inverter, while C3 and C4 form the doubler. C1 and C3
are the pump capacitors; C2 and C4 are the reservoir
capacitors. Because both the inverter and doubler use
part of the charge-pump circuit, loading either output
causes both outputs to decline toward GND. Make sure
the sum of the currents drawn from the two outputs
does not exceed 30mA.
SHDN
2
3
C1
4
3
+VIN
2
C1
4
3
MAX16945
4
C1
6
1
MAX16945
6
1
6
1
VOUT = -VIN
VOUT
C2
D2
C2
5
C2
D1, D2 = 1N4148
2
D1
MAX16945
…
5
+VIN
5
…
C4
C3
SHDN
VOUT = (2VIN) (VFD1) - (VFD2)
VOUT = -nVIN
Figure 4. Cascading MAX16945s to Increase Output Voltage
Figure 6. Combined Doubler and Inverter
Paralleling Devices
Heavy Load Connected
to a Positive Supply
Paralleling multiple MAX16945s reduces the output
resistance. Each device requires its own charge-pump
capacitor (C1), but the reservoir capacitor (C2) serves
all devices (Figure 5). Increase C2’s value by a factor
of n, where n is the number of parallel devices. Figure 5
shows the equation for calculating output resistance.
Under heavy loads, where a higher supply is sourcing
current into OUT, the OUT supply must not be pulled
above ground. Applications that sink heavy current into
OUT require a Schottky diode (1N5817) between GND
and OUT, with the anode connected to OUT (Figure 7).
+VIN
…
GND
2
2
3
C1
3
MAX16945
4
C1
1
6
…
5
SHDN
MAX16945
MAX16945
1
VOUT
1
Figure 7. Heavy Load Connected to a Positive Supply
5
VOUT = -VIN
V+
RL
OUT
4
6
4
Layout and Grounding
C2
ROUT OF SINGLE DEVICE
ROUT = NUMBER OF DEVICES
Figure 5. Paralleling MAX16945s to Reduce Output Resistance
Good layout is important, primarily for good noise performance. To ensure good layout, mount all components as close together as possible, keep traces short
to minimize parasitic inductance and capacitance, and
use a ground plane.
Chip Information
PROCESS: BiCMOS
_______________________________________________________________________________________
7
MAX16945
Cascading Devices
Two devices can be cascaded to produce an even larger
negative voltage (Figure 4). The unloaded output voltage
is normally -2 x VIN, but this is reduced slightly by the output resistance of the first device when multiplied by the
quiescent current of the second. When cascading more
than two devices, the output resistance rises dramatically. The maximum load current and startup current of
the nth cascaded circuit must not exceed the maximum
output current capability of the (n-1)th circuit to ensure
proper startup.
MAX16945
30mA Inverting Charge Pump in SOT23
for EMI-Sensitive Automotive Applications
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
6 SOT23
U6F-6
21-0058
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2008 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
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