MAX1793 Low-Dropout, Low I , 1A Linear Regulator Q

MAX1793 Low-Dropout, Low I , 1A Linear Regulator Q
19-1654; Rev 1; 11/00
Low-Dropout, Low IQ, 1A Linear Regulator
Features
♦ Guaranteed 1A Output Current
♦ Low 210mV Dropout at 1A
♦ Up to ±1% Output Voltage Accuracy
Preset at 1.5V, 1.8V, 2.0V, 2.5V, 3.3V or 5.0V
Adjustable from 1.25V to 5.0V
♦ Reset Output (4ms delay)
♦ Low 125µA Ground Current
♦ 0.1µA Shutdown
♦ Low 115µVRMS Output Noise
♦ Thermal Overload Protection
♦ Output Current Limit
♦ Tiny TSSOP Power Package (1.5W)
30% Smaller than SOT223 (only 1.1mm high)
Ordering Information
________________________Applications
TEMP.
RANGE
PART
PINPACKAGE
†
VOUT (V)
MAX1793EUE-50 -40°C to +85°C 16 TSSOP-EP* 5.0 or Adj
Notebook Computers
MAX1793EUE-33 -40°C to +85°C 16 TSSOP-EP* 3.3 or Adj
Cordless Telephones
Cellular Phones
Modems
Hand-Held Instruments
PDAs and Palmtop Computers
MAX1793EUE-25 -40°C to +85°C 16 TSSOP-EP
2.5 or Adj
MAX1793EUE-20 -40°C to +85°C 16 TSSOP-EP
2.0 or Adj
MAX1793EUE-18 -40°C to +85°C 16 TSSOP-EP
1.8 or Adj
MAX1793EUE-15 -40°C to +85°C 16 TSSOP-EP
1.5 or Adj
*EP = Exposed Pad
† Contact factory for other preset output voltages.
Typical Operating Circuit
Pin Configuration
TOP VIEW
IN
NC
IN
IN
IN
CIN
ON
OUT
MAX1793
OUT
OUT
IN
OUT
SHDN
RST
OFF
SET
GND
OUT
COUT
N.C. 1
16 N.C.
IN 2
15 OUT
IN 3
IN 4
RESET
OUTPUT
14 OUT
MAX1793
13 OUT
IN 5
12 OUT
RST 6
11 SET
SHDN 7
10 GND
N.C. 8
9
N.C.
TSSOP-EP
________________________________________________________________ Maxim Integrated Products
1
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX1793
General Description
The MAX1793 low-dropout linear regulator (LDO) operates from +2.5V to +5.5V and delivers a guaranteed 1A
load current with a low 210mV dropout. The high-accuracy (±1%) output voltage is preset at an internally
trimmed voltage (see Ordering Information) or can be
adjusted from 1.25V to 5.0V with an external resistordivider.
An internal PMOS pass transistor allows a low 125µA
supply current, making the MAX1793 ideal for batteryoperated portable equipment. Other features include a
built-in reset output, low-power shutdown, and short-circuit and thermal overload protection. The MAX1793 is
available in a 1.5W, 16-pin power TSSOP package,
which is 30% smaller than a SOT223 package and only
1.1mm high.
MAX1793
Low-Dropout, Low IQ, 1A Linear Regulator
ABSOLUTE MAXIMUM RATINGS
IN, SHDN, RST to GND ............................................-0.3V to +6V
OUT, SET to GND ........................................-0.3V to (VIN + 0.3V)
Output Short-Circuit Duration ............................................Infinite
Continuous Power Dissipation (TA = +70°C)
16-Pin TSSOP-EP (derate 19mW/°C above +70°C)........1.5W
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+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
(VIN = VOUT(NOM) + 0.5V or VIN = 2.5V (whichever is greater), SHDN = IN, TA = +0°C to +85°C, unless otherwise noted. Typical values
are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Input Voltage
VIN
2.5
5.5
V
Input Undervoltage Lockout
VIN
2.0
2.3
V
Preset VOUT ≥ 2.5V
-1
1
Preset VOUT < 2.5V
TA = +85°C,
IOUT = 250mA
Output Voltage Accuracy
(preset mode, SET = GND)
SET Voltage Threshold
(for adjustable output)
-1.5
+1.5
TA = 0°C to +85°C, IOUT = 250mA
-2
2
TA = 0°C to +85°C, IOUT = 1mA to 1A,
VIN > VOUT + 0.5V
-3
3
TA = +85°C, IOUT = 250mA, VIN = 3V
1.229
TA = 0°C to +85°C, IOUT = 250mA, VIN = 3V
1.219
1.281
TA = 0°C to +85°C, IOUT = 1mA to 1A, VIN = 3V
1.212
1.288
1.25
5
Adjustable Output Voltage
Range
Maximum Output Current
IOUT
Short-Circuit Current Limit
ILIM
Continuous, VIN = ≥3V
VOUT = 0, VIN = ≥3V
1.1
SET Pin Dual Mode Threshold
ISET
VSET = +1.25V
Ground Current
IGND
IOUT = 100µA
Dropout Voltage (Note 1)
VIN - VOUT
IOUT = 1A,
SET = GND
V
V
ARMS
1.8
3.3
2.8
50
SET Input Bias Current
1.271
1
VOUT within 4% of nominal output voltage,
VIN = 5.5V
In-Regulation Current Limit
1.250
%
A
A
150
mV
±100
nA
125
200
µA
MAX1793-33, -50
210
350
MAX1793-25
270
450
0
0.15
mV
Line Regulation
∆VLNR
VIN from (VOUT + 0.1V) to +5.5V,
IOUT = 5mA, SET = GND
Load Regulation
∆VLDR
IOUT = 100µA to 1A
0.7
%
10Hz to 1MHz, COUT = 6.8µF (ESR < 0.1Ω)
115
µVRMS
SHDN = GND, VIN = +5.5V
0.1
Output Voltage Noise
Shutdown Supply Current
IOFF
Output Pulldown Resistance in
Shutdown
SHDN Input Threshold
SHDN Input Bias Current
2
-0.15
SHDN = GND
VIH
VIL
+2.5V < VIN < +5.5V
I SHDN
SHDN = GND or IN
16
5
_______________________________________________________________________________________
µA
kΩ
1.6
0.01
%/V
0.6
1
V
µA
Low-Dropout, Low IQ, 1A Linear Regulator
(VIN = VOUT(NOM) + 0.5V or VIN = 2.5V (whichever is greater), SHDN = IN, TA = +0°C to +85°C, unless otherwise noted. Typical values
are at TA = +25°C.)
PARAMETER
RST Output Low Voltage
SYMBOL
VOL
CONDITIONS
MIN
TYP
MAX
UNITS
0.1
V
5.5
V
0.01
1
µA
ISINK = 1mA
Operating Voltage Range for
RST Valid
ISINK = 100µA
RST Output High Leakage
V RST = +5.5V
RST Trip Level Referred to
Nominal VOUT
Rising edge
90
94
96
% VOUT
RST Release Delay
Rising edge
1.5
4.0
8.0
ms
Thermal Shutdown Temperature
T SHDN
1.0
Typical thermal hysteresis = 20°C
170
°C
ELECTRICAL CHARACTERISTICS
(VIN = VOUT(NOM) + 0.5V or VIN = 2.5V (whichever is greater), SHDN = IN, TA = -40°C to +85°C, unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
Input Voltage
VIN
Input Undervoltage Lockout
VIN
CONDITIONS
MIN
MAX
UNITS
2.5
TYP
5.5
V
V
2.0
2.3
Output Voltage Accuracy
(preset mode, SET = GND)
IOUT = 250mA
-2.5
2.5
IOUT = 1mA to 1A, VIN > VOUT + 0.5V
-3.2
3.2
SET Voltage Threshold
(for adjustable output)
IOUT = 250mA, VIN = 3V
1.216
1.284
IOUT = 1mA to 1A, VIN = 3V
1.210
1.290
1.25
5
Adjustable Output Voltage
Range
Maximum Output Current
IOUT
Continuous, VIN ≥ 3V
Short-Circuit Current Limit
ILIM
VOUT = 0, VIN ≥ 3V
V
V
ARMS
1
SET Pin Dual Mode Threshold
%
1.1
3.3
A
50
150
mV
SET Input Bias Current
ISET
VSET = +1.25V
±100
nA
Ground Current
IGND
IOUT = 100µA
200
µA
Dropout Voltage (Note 1)
VIN VOUT
IOUT = 1A,
SET = GND
Line Regulation
∆VLNR
VIN from (VOUT + 0.1V) to +5.5V,
IOUT = 5mA, SET = GND
Shutdown Supply Current
SHDN Input Threshold
IOFF
VIH
VIL
SHDN Input Bias Current
ISH D N
RST Output Low Voltage
VOL
MAX1793-33, -50
350
MAX1793-25
450
-0.15
SHDN = GND, VIN = +5.5V
+2.5V < VIN < +5.5V
SHDN = GND or IN
ISINK = 1mA
mV
0.15
%/V
16
µA
1.6
0.6
V
1
µA
0.1
V
_______________________________________________________________________________________
3
MAX1793
ELECTRICAL CHARACTERISTICS (continued)
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VOUT(NOM) + 0.5V or VIN = 2.5V (whichever is greater), SHDN = IN, TA = -40°C to +85°C, unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
Operating Voltage Range for
RST Valid
ISINK = 10µA
RST Output High Leakage
V RST = +5.5V
RST Trip Level Referred to
Nominal VOUT
Rising edge
RST Release Delay
Rising edge
MIN
TYP
1.0
MAX
UNITS
5.5
V
1
µA
90
96
% VOUT
1.5
8.0
ms
Note 1: Dropout voltage is defined as VIN - VOUT, when VOUT is 100mV below the value of VOUT measured when VIN = VOUT(NOM) +
0.5V. Since the minimum input voltage is 2.5V, this specification in only meaningful when VOUT(NOM) ≥2.5V. For VOUT(NOM)
between 2.5V and 3.3V, use the following equations: Typical Dropout = 210mV + (3.3V - VOUT(NOM) x 75mV/V; Guaranteed
Maximum Dropout = 350mV + (3.3V - VOUT(NOM) x 125mV/V. For VOUT(NOM) > 3.3V: Typical Dropout = 210mV;
Guaranteed Maximum Dropout = 350mV.
Note 2: Specifications to -40°C are guaranteed by design and not production tested.
Typical Operating Characteristics
(Circuit of Figure 2, VIN = +5V, V SHDN = VIN, VOUT = +3.3V, TA = +25°C, unless otherwise noted.)
3.299
3.297
IOUT = 1A
2.5
2.0
1.5
1.0
IOUT = 250mA
3.315
3.310
3.305
3.300
3.295
3.290
3.285
3.280
0.5
3.275
3.270
0
3.293
1
10
100
0
1000
1
3
4
225
150
IOUT = 0
50
175
150
125
100
75
2
3
INPUT VOLTAGE (V)
4
5
40
60
80
190
180
170
160
150
IOUT = 0
140
50
130
25
120
110
0
0
20
IOUT = 250mA
200
GROUND CURRENT (µA)
200
GROUND CURRENT (µA)
200
0
GROUND CURRENT vs. TEMPERATURE
210
MAX1793 toc05
250
MAX1793 toc04
IOUT = 1A
1
-20
TEMPERATURE (°C)
GROUND CURRENT vs. LOAD CURRENT
GROUND CURRENT vs. INPUT VOLTAGE
250
0
-40
5
INPUT VOLTAGE (V)
LOAD CURRENT (mA)
100
2
MAX1793 toc06
3.295
4
MAX1793 toc03
IOUT = 0
3.0
OUTPUT VOLTAGE (V)
3.301
3.320
MAX1793 toc02
MAX1793 toc01
3.5
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
3.303
OUTPUT VOLTAGE vs. TEMPERATURE
OUTPUT VOLTAGE vs. INPUT VOLTAGE
OUTPUT VOLTAGE vs. LOAD CURRENT
3.305
GROUND CURRENT (µA)
MAX1793
Low-Dropout, Low IQ, 1A Linear Regulator
1
10
100
LOAD CURRENT (mA)
1000
-40
-20
0
20
40
TEMPERATURE (°C)
_______________________________________________________________________________________
60
80
Low-Dropout, Low IQ, 1A Linear Regulator
50
200
10
150
30
100
20
50
10
0
400
600
1000 1200
LOAD CURRENT (mA)
0.1
IOUT = 250mA
0.01
0
800
1
0.01
0.1
1
10
100
0.01
1000
0.1
1
10
100
1000
FREQUENCY (kHz)
FREQUENCY (kHz)
OUTPUT NOISE vs. LOAD CURRENT
LINE-TRANSIENT RESPONSE
MAX1793 toc11
140
MAX1793 toc10
200
120
5V
VIN
OUTPUT NOISE (µVRMS)
0
NOISE (µV/√Hz)
PSRR (dB)
40
MAX1793 toc09
IOUT = 250mA
MAX1793 toc08
250
DROPOUT VOLTAGE (mV)
60
MAX1793 toc07
300
OUTPUT NOISE SPECTRAL DENSITY
vs. FREQUENCY
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
DROPOUT VOLTAGE vs. LOAD CURRENT
100
3.4V
80
60
VOUT
40
10mV/div
AC-COUPLED
20
IOUT = 100mA
0
0.001
0.01
0.1
1
100µs/div
LOAD CURRENT (A)
LOAD-TRANSIENT RESPONSE
OUTPUT NOISE
MAX1793 toc12
MAX1793 toc13
1A
IOUT
100mA
100µV/div
20mV/div
AC-COUPLED
VOUT
40µs/div
4ms/div
_______________________________________________________________________________________
5
MAX1793
Typical Operating Characteristics (continued)
(Circuit of Figure 2, VIN = +5V, V SHDN = VIN, VOUT = +3.3V, TA = +25°C, unless otherwise noted.)
MAX1793
Low-Dropout, Low IQ, 1A Linear Regulator
Typical Operating Characteristics (continued)
(Circuit of Figure 2, VIN = +5V, V SHDN = VIN, VOUT = +3.3V, TA = +25°C, unless otherwise noted.)
RESET OUTPUT RESPONSE
SHUTDOWN RESPONSE
MAX1793 toc15
MAX1793 toc14
VOUT
VIN
5V/div
VOUT
2V/div
RST
2V/div
2V/div
VSHDN
5V/div
IOUT = 100mA
1ms/div
40µs/div
Pin Description
6
PIN
NAME
FUNCTION
1, 8, 9,
16
N.C.
2, 3, 4,
5
IN
6
RST
7
SHDN
Active-Low Shutdown Input. A logic low disables the output and reduces the supply current to 0.1µA. In
shutdown, the RST output is low and OUT is pulled low through an internal 5kΩ resistance. Connect SHDN
to IN for normal operation.
10
GND
Ground. This pin and the exposed pad also function as a heatsink. Solder both to a large pad or to the
circuit-board ground plane to maximize power dissipation.
11
SET
Voltage-Setting Input. Connect to GND to select the factory-preset output voltage. Connect SET to an
external resistor-divider for adjustable-output operation.
12, 13,
14, 15
OUT
Regulator Output. Bypass with a 6.8µF low-ESR capacitor to GND. Connect all OUT pins together at the IC.
No Connection. Not internally connected.
Regulator Input. Supply voltage ranges from +2.5V to +5.5V. Bypass with a 4.7µF capacitor to GND (see
Capacitor Selection and Regulator Stability). These inputs are internally connected, but they also must be
externally connected for proper operation.
Reset Output. Open-drain output is low when VOUT is 6% below its nominal value. RST remains low while the
output voltage (VOUT) is below the reset threshold and for at least 4ms after VOUT rises above the reset
threshold. Connect a 100kΩ pull-up resistor to OUT to obtain an output voltage.
_______________________________________________________________________________________
Low-Dropout, Low IQ, 1A Linear Regulator
The MAX1793 features Dual Mode™ operation, allowing a fixed output or an adjustable output from +1.25V
to +5V. The regulators are guaranteed to supply 1A of
output current.
As Figure 1 shows, the device consists of a +1.25V reference, error amplifier, MOSFET driver, P-channel pass
transistor, internal feedback voltage-divider, Dual Mode
comparator, and 4ms reset output.
The +1.25V reference is connected to the inverting
input of the error amplifier. The error amplifier compares this reference with the selected feedback voltage
and amplifies the difference. The MOSFET driver reads
the error signal and applies the appropriate drive to the
P-channel transistor. If the feedback voltage is lower
than the reference, the pass transistor’s gate is pulled
lower, allowing more current to pass and increase the
output voltage. If the feedback voltage is high, the pass
transistor’s gate is pulled up, allowing less current to
pass to the output. The low VOUT comparator senses
when the feedback voltage has dropped 6% below its
expected level, causing RST to go low.
The output voltage is fed back through either an internal resistor-divider connected to OUT or an external
resistor network connected to SET. The Dual Mode
comparator examines VSET and selects the feedback
path. If VSET is below 50mV, the internal feedback path
is used and the output is regulated to the factory-preset
voltage.
Dual Mode is a trademark of Maxim Integrated Products.
IN
SHUTDOWN
THERMAL
SENSOR
MOSFET DRIVER
WITH FOLDBACK
CURRENT LIMIT
ERROR AMP
SHDN
PMOS
SHUTDOWN
LOGIC
OUT
94% VOUT
DETECTOR
4ms DELAY TIMER
IN
RST
NMOS
1.25V
REFERENCE
OUT
1175mV
4ms
SET
R1
MAX1793
DUAL MODE
COMPARATOR
100mV
R2
GND
Figure 1. Functional Diagram
_______________________________________________________________________________________
7
MAX1793
Detailed Description
MAX1793
Low-Dropout, Low IQ, 1A Linear Regulator
Internal P-Channel Pass Transistor
Shutdown
The MAX1793 features a 1A P-channel MOSFET pass
transistor. Unlike similar designs using PNP pass transistors, P-channel MOSFETs require no base drive,
which reduces quiescent current. PNP-based regulators also waste considerable current in dropout when
the pass transistor saturates and use high base-drive
currents under large loads. The MAX1793 does not suffer from these problems and consumes only 225µA of
quiescent current under heavy loads, as well as in
dropout.
A logic low on SHDN disables the MAX1793. In shutdown, the pass transistor, control circuitry, reference,
and all internal circuits are turned off, reducing supply
current to typically 0.1µA. Connect SHDN to IN for normal operation. In shutdown, RST goes low and OUT is
discharged to GND with a 5kΩ internal resistance.
Output Voltage Selection
The MAX1793 features Dual Mode operation. In preset
voltage mode, the output of the MAX1793 is set to an
internally trimmed voltage (see Ordering Information).
Select this mode by connecting SET to GND (Figure 2).
In adjustable mode, an output is selected between
+1.25V and +5V using two external resistors connected
as a voltage divider to SET (Figure 3). The output voltage is determined by the following equation:
VOUT = VSET [1 + (R1 / R2)]
where VSET = +1.25V. To simplify resistor selection:
R1 = R2 [(VOUT / VSET) – 1]
Since the input bias current at SET is less than 100nA,
large resistance values can be used for R1 and R2 to
minimize power consumption without losing efficiency.
Up to 125kΩ is acceptable for R2.
In preset voltage mode, the impedance from SET to
GND should be less than 10kΩ. Otherwise, spurious
conditions could cause the voltage at SET to exceed
the 50mV dual-mode threshold.
RST Comparator
The MAX1793 features a low VOUT indicator that asserts
when the output voltage falls out of regulation. The
open-drain RST output goes low when OUT falls 6%
below its nominal output voltage. RST remains low for
4ms after OUT has returned to its nominal value. A
100kΩ pull-up resistor from RST to a suitable logic supply voltage (typically OUT) provides a logic control signal. RST can be used as a power-on-reset (POR) signal
to a microcontroller or can drive an external LED to indicate power failure. RST is low during shutdown.
Current Limiting
The MAX1793 features a current limit that monitors the
pass transistor, typically limiting short-circuit output
current to 1.8A. The current limit is increased to
approximately 2.8A when the output voltage is in regulation, improving performance with large transient
loads. The output can be shorted to ground for an
indefinite period of time without damaging the device.
Thermal Overload Protection
Thermal overload protection limits total power dissipation in the MAX1793. When the junction temperature
exceeds TJ = +170°C, a thermal sensor turns off the
pass transistor, allowing the IC to cool. The thermal sensor turns the pass transistor on once the IC’s junction
IN
NC
IN
IN
IN
NC
IN
IN
CIN = 4.7µF
ON
OFF
OUT
MAX1793
OUT
IN
OUT
IN
OUT
SHDN
RST
SET
CIN = 4.7µF
IN
OUT
COUT = 6.8µF
ON
OFF
RESET
OUTPUT
OUT
MAX1793
OUT
OUT
OUT
IN
OUT
SHDN
RST
COUT = 6.8µF
R1
RESET
OUTPUT
GND
SET
R2
GND
Figure 2. Typical Operating Circuit with Preset Output Voltage
8
Figure 3. Typical Operating Circuit with Adjustable Output
Voltage
_______________________________________________________________________________________
Low-Dropout, Low IQ, 1A Linear Regulator
PMAX = [(TJ(MAX) – TA) / (θJC + θCA)]
MAXIMUM OUTPUT CURRENT vs.
INPUT-OUTPUT DIFFERENTIAL VOLTAGE
2.0
MAXIMUM CONTINUOUS CURRENT
1.8
1.6
MAXIMUM SUPPLY VOLTAGE
MAXIMUM OUTPUT CURRENT (A)
Operating Region and Power Dissipation
Maximum power dissipation of the MAX1793 depends
on the thermal resistance of the case and circuit board,
the temperature difference between the die junction
and ambient air, and the rate of air flow. The power dissipated by the device is: P = IOUT (VIN – VOUT). The
resulting maximum power dissipation is:
MAX1793
temperature drops approximately 20°C. Continuous
short-circuit conditions will result in a pulsed output.
Thermal overload protection is designed to safeguard
the MAX1793 in the event of fault conditions. For continuous operation, do not exceed the absolute maximum junction-temperature rating of TJ = +150°C.
TA = +25°C
1.4
1.2
1.0
0.8
0.6
TA = +50°C
0.4
TA = +70°C
0.2
TJ(MAX) = +150°C
0
0
1
2
3
4
5
6
INPUT-OUTPUT DIFFERENTIAL VOLTAGE (V)
where (T J(MAX) – T A ) is the temperature difference
between the maximum allowed die junction (+150°C)
and the surrounding air, θJC (junction-to-case) is the
thermal resistance of the package chosen, and θCA is
the thermal resistance from the case through the PC
board, copper traces, and other materials to the surrounding air. Figure 4 shows allowable power dissipation for typical PC boards at +25°C, +50°C, and +70°C
ambient temperatures.
The MAX1793 TSSOP-EP package features an exposed
thermal pad on its underside. This pad lowers the thermal resistance of the package by providing a direct heat
conduction path from the die to the PC board.
Additionally, the ground pin (GND) also channels heat.
Connect the exposed thermal pad and GND to circuit
ground by using a large pad (minimum 1in2 recommended), or multiple vias to the ground plane.
Applications Information
Capacitor Selection
and Regulator Stability
Capacitors are required at the input and output of the
MAX1793. Connect a 4.7µF capacitor between IN and
ground (CIN) and a 6.8µF capacitor between OUT and
ground (COUT). CIN serves only to lower the source
impedance of the input supply and may be smaller than
4.7µF when the MAX1793 is powered from regulated
power supplies or low-impedance batteries.
The output capacitor’s equivalent series resistance (ESR)
affects stability and output noise. COUT ESR should be
0.5Ω or less to ensure stability and optimum transient
response. Surface-mount ceramic capacitors have very
low ESR and are commonly available in values up to
10µF. Other low-ESR (< 0.5Ω) capacitors, such as surface-mount tantalum or OS-CON, may also be used.
Figure 4. Power Operating Region: Maximum Output Current
vs. Input-Output Differential Voltage
Connect CIN and COUT as close to the IC as possible to
minimize the impact of PC board trace inductance.
Noise, PSRR, and Transient Response
MAX1793 output noise is typically 115µVRMS during normal operation. This is suitably low for most applications.
See the output noise plot in the Typical Operating
Characteristics.
The MAX1793 is designed to achieve low dropout voltage and low quiescent current in battery-powered systems while still maintaining good noise, transient
response, and AC rejection. See the Typical Operating
Characteristics for a plot of power-supply rejection ratio
(PSRR) versus frequency. When operating from very
noisy sources, supply noise rejection and transient
response can be improved by increasing the values of
the input and output capacitors and employing passive
postfiltering.
Input-Output (Dropout) Voltage
A regulator’s minimum input-to-output voltage differential
(dropout voltage) determines the lowest usable supply
voltage. In battery-powered systems, this determines the
useful end-of-life battery voltage. Since a P-channel
MOSFET is used as the pass device, dropout voltage is
the product of RDS(ON) and load current (see Electrical
Characteristics and Dropout Voltage vs. Load Current in
the Typical Operating Characteristics). The MAX1793
operating current typically remains below 225µA in
dropout.
Chip Information
TRANSISTOR COUNT: 845
_______________________________________________________________________________________
9
Low-Dropout, Low IQ, 1A Linear Regulator
TSSOP, 4.0,EXP PADS.EPS
MAX1793
Package Information
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.
10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2000 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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