19-1812; Rev 0; 1/01
500mA, Low-Dropout,
Ripple-Rejecting LDO in µMAX
General Description
The MAX1857 low-dropout linear regulator operates
from a +2.5V to +5.5V supply and delivers a guaran-
teed 500mA load current with low 120mV dropout. The
high-accuracy (±1%) output voltage is preset at an
internally trimmed 4.75V or can be adjusted from 1.25V
to 5.0V with an external resistive divider.
An internal PMOS pass transistor allows the low 135µA
supply current to remain independent of load, making
this device ideal for portable battery-operated equip-
ment such as personal digital assistants (PDAs), cellu-
lar phones, cordless phones, base stations, and
notebook computers.
Other features include an active-low open-drain reset
output with a 4.5ms timeout period that indicates when
the output is out of regulation, a 0.1µA shutdown mode,
short-circuit protection, and thermal shutdown protec-
tion. The device is available in a miniature 8-pin µMAX
package. For higher power applications, refer to the
MAX1792 and MAX1793 data sheets.
o
Guaranteed 500mA Output Current
o
Low 120mV Dropout at 500mA
o
Up to ±1% Output Voltage Accuracy
Preset at 4.75V
Adjustable from 1.25V to 5.0V
o
Reset Output with 4.5ms Timeout Period
o
Low 135µA Ground Current
o
0.1µA Shutdown Current
o
Thermal Overload Protection
o
Output Current Limit
o
Tiny µMAX Package
Features
MAX1857
________________________Applications
Notebook Computers
Cellular and Cordless Telephones
PDAs
Palmtop Computers
Base Stations
USB Hubs
Docking Stations
PART*
MAX1857EUA47
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
8
µMAX
*Contact factory for other preset output voltages.
Typical Operating Circuit
V
IN
= +5V
IN
NC
C
IN
1µF
Pin Configuration
TOP VIEW
V
OUT
= 4.75V
OUT
OUT
C
OUT
3.3µF
IN
IN
1
IN
2
RST
3
8
7
OUT
OUT
SET
GND
MAX1857
ON
SHDN
OFF
RST
R
RST
100k
TO
µC
MAX1857
6
5
SHDN
4
SET
GND
µMAX
________________________________________________________________
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.
500mA, Low-Dropout,
Ripple-Rejecting LDO in µMAX
MAX1857
ABSOLUTE MAXIMUM RATINGS
IN,
SHDN, RST,
SET to GND ....................................-0.3V to +6V
OUT to GND ................................................-0.3V to (V
IN
+ 0.3V)
Output Short-Circuit Duration ........................................Indefinite
Continuous Power Dissipation (T
A
= +70°C)
8-Pin µMAX (derate 4.5mW/°C above +70°C) .............362mW
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
(V
IN
= +5.25V, V
OUT
= 4.75V,
SHDN
= IN, SET = GND,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Input Voltage
Input Undervoltage Lockout
SYMBOL
V
IN
V
UVLO
Rising, 75mV hysteresis
I
OUT
= 100mA,
T
A
= +85°C
Output Voltage Accuracy
(Preset Mode)
V
OUT
V
OUT
≥
2.5V
V
OUT
< 2.5V
CONDITIONS
MIN
2.5
2.0
-1
-1.5
-2
-3
1.25
T
A
= +85°C
T
A
= 0°C to +85°C
1.229
1.219
500
0.55
50
I
SET
I
Q
V
IN
-
V
OUT
∆V
LNR
∆V
LDR
V
SET
= 1.25V
I
OUT
= 1mA
I
OUT
= 500mA
I
OUT
= 500mA
V
IN
from (V
OUT
+ 100mV) to 5.5V,
I
LOAD
= 5mA
I
OUT
= 1mA to 500mA
10Hz to 1MHz, C
OUT
= 3.3µF (ESR < 0.1Ω)
I
OFF
V
IH
V
IL
SHDN
= GND, V
IN
= 5.5V
2.5V < V
IN
< 5.5V
2.5V < V
IN
< 5.5V
SHDN
= IN or GND
1.6
0.6
10
100
-0.15
-100
135
175
120
0
0.4
115
0.1
15
175
+0.15
1.0
1.2
2.0
100
150
+100
250
2.2
1.250
2.15
TYP
MAX
5.5
2.3
+1
+1.5
+2
+3
5
1.271
V
1.281
mA
RMS
A
A
mV
nA
µA
mV
%/V
%
µV
RMS
µA
V
nA
%
UNITS
V
V
%
I
OUT
= 100mA, T
A
= 0°C to +85°C
I
OUT
= 1mA to 500mA, V
IN
> V
OUT
+ 0.5V,
T
A
= 0°C to +85°C
Adjustable Output Voltage
Range
SET Voltage Threshold
(Adjustable Mode)
Maximum Output Current
Short-Circuit Current Limit
In-Regulation Current Limit
SET Dual Mode™ Threshold
SET Input Bias Current
Ground-Pin Current
Dropout Voltage (Note 1)
Line Regulation
Load Regulation
Output Voltage Noise
SHUTDOWN
Shutdown Supply Current
SHDN
Input Threshold
SHDN
Input Bias Current
V
SET
I
OUT
I
LIM
V
SET
= 1.25V
V
IN
= +2.7V,
V
OUT
set to 2.0V,
I
OUT
= 100mA
V
IN
≥
2.7V
V
OUT
= 0, V
IN
≥
2.7V
V
OUT
> 96% of nominal value, V
IN
≥
2.7V
V
Dual Mode is a trademark of Maxim Integrated Products.
2
_______________________________________________________________________________________
500mA, Low-Dropout,
Ripple-Rejecting LDO in µMAX
ELECTRICAL CHARACTERISTICS (continued)
((V
IN
= +5.25V, V
OUT
= 4.75V,
SHDN
= IN, SET = GND,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
RESET OUTPUT
Reset Output Low Voltage
Operating Voltage Range for
Valid Reset
RST
Output High Leakage
Current
RST
Threshold
RST
Release Delay
THERMAL PROTECTION
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
T
SHDN
∆T
SHDN
170
20
°C
°C
t
RP
V
OL
RST
sinking 1mA
RST
sinking 100µA
V
RST
= +5.5V
Rising edge, referred to V
OUT(NOMINAL)
Rising edge of OUT to rising edge of
RST
83
1.4
86
4.5
1.0
0.01
0.1
5.5
100
89
8
V
V
nA
%
ms
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1857
ELECTRICAL CHARACTERISTICS
(V
IN
= +5.25V, V
OUT
= 4.75V,
SHDN
= IN, SET = GND,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 2)
PARAMETER
Input Voltage
Input Undervoltage Lockout
Output Voltage Accuracy
(Preset Mode)
Adjustable Output Voltage
Range
SET Voltage Threshold
(Adjustable Mode)
Maximum Output Current
Short-Circuit Current Limit
SET Dual Mode Threshold
SET Input Bias Current
Ground-Pin Current
Dropout Voltage (Note 1)
Line Regulation
Load Regulation
SHUTDOWN
Shutdown Supply Current
SHDN
Input
Threshold
SHDN
Input Bias Current
I
OFF
V
IH
V
IL
SHDN
= GND, V
IN
= +5.5V
2.5V < V
IN
< 5.5V
2.5V < V
IN
< 5.5V
SHDN
= IN or GND
1.6
0.6
100
15
µA
V
nA
I
SET
I
Q
V
IN
-
V
OUT
∆V
LNR
∆V
LDR
V
SET
= 1.25V
I
OUT
= 1mA
I
OUT
= 500mA
V
IN
from (V
OUT
+ 100mV) to 5.5V,
I
LOAD
= 5mA
I
OUT
= 1mA to 500mA
-0.15
V
SET
I
OUT
I
LIM
V
OUT
= 0
SYMBOL
V
IN
V
UVLO
V
OUT
Rising or falling
I
OUT
= 1mA to 500mA
V
SET
= 1.25V
I
OUT
= 100mA
CONDITIONS
MIN
2.5
2.0
-3
1.25
1.212
500
0.55
50
-100
2.2
150
+100
250
175
+0.15
1.0
MAX
5.5
2.3
+3
5
1.288
UNITS
V
V
%
V
V
mA
RMS
A
mV
nA
µA
mV
%/V
%
_______________________________________________________________________________________
3
500mA, Low-Dropout,
Ripple-Rejecting LDO in µMAX
MAX1857
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= +5.25V, V
OUT
= 4.75V,
SHDN
= IN, SET = GND,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 2)
PARAMETER
RESET OUTPUT
Reset Output Low Voltage
Operating Voltage Range for
Valid Reset
RST
Output High Leakage
Current
RST
Threshold
RST
Release Delay
t
RP
V
OL
RST
sinking 1mA
RST
sinking 100µA
V
RST
= +5.5V
Rising edge, referred to V
OUT(NOMINAL)
Rising edge of OUT to rising edge of
RST
83
1.4
1.0
0.1
5.5
100
89
8
V
V
nA
%
ms
SYMBOL
CONDITIONS
MIN
MAX
UNITS
Note 1:
Dropout voltage is defined as V
IN
- V
OUT
, when V
OUT
is 100mV below the value of V
OUT
measured when V
IN
= V
OUT(NOM)
+ 0.5V. Since the minimum input voltage is 2.5V, this specification is only meaningful when V
OUT(NOM)
≥
2.5V. For V
OUT(NOM)
between 2.5V and 3.5V, use the following equations: Typical Dropout = -93mV/V
✕
V
OUT(NOM)
+ 445mV; Guaranteed Maximum
Dropout = -137mV/V
✕
V
OUT(NOM)
+ 704mV. For V
OUT(NOM)
≥
3.5V: Typical Dropout = 120mV; Guaranteed Maximum Dropout
= 175mV.
Note 2:
Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(V
IN
= +5.25V, V
OUT
= 4.75V,
SHDN
= IN, SET = GND, C
IN
= 1µF, C
OUT
= 3.3µF, T
A
= +25°C, unless otherwise noted.)
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX1857 toc01
OUTPUT VOLTAGE vs. TEMPERATURE
I
OUT
= 0mA
MAX1857 toc02
DROPOUT VOLTAGE
vs. OUTPUT CURRENT
T
A
= +85°C
250
DROPOUT VOLTAGE (mV)
T
A
= +25°C
200
150
100
50
0
T
A
= -40°C
MAX1857 toc03
4.80
4.80
300
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
1000
4.76
4.78
V
IN
= 5.25V
4.76
4.72
V
IN
= 5.00V
4.68
4.74
4.72
4.64
0
200
400
600
800
OUTPUT CURRENT (mA)
4.70
-55
-25
5
35
65
95
125
TEMPERATURE (°C)
0
200
400
600
800
1000
OUTPUT CURRENT (mA)
4
_______________________________________________________________________________________
500mA, Low-Dropout,
Ripple-Rejecting LDO in µMAX
MAX1857
Typical Operating Characteristics (continued)
(V
IN
= +5.25V, V
OUT
= 4.75V,
SHDN
= IN, SET = GND, C
IN
= 1µF, C
OUT
= 3.3µF, T
A
= +25°C, unless otherwise noted.)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
70
60
PSRR (dB)
50
40
30
20
10
0
0.01
0.1
1
10
100
1000
FREQUENCY (kHz)
10µs/div
A: V
OUT
= 4.75V, 50mV/div
B: I
OUT
= 5mA TO 500mA, 200mA/div
V
IN
= 5.25V, C
IN
= 10µF
C
OUT
= 3.3µF
I
OUT
= 50mA
MAX1857 toc04
LOAD-TRANSIENT RESPONSE
MAX1857 toc05
80
4.80V
4.75V
4.70V
600mA
400mA
B
200mA
0
A
LOAD-TRANSIENT RESPONSE
NEAR DROPOUT
MAX1857 toc06
SWITCHING POWER-SUPPLY
RIPPLE REJECTION
MAX1857 toc07
4.80V
4.75V
4.70V
4.65V
400mA
200mA
0
10µs/div
A: V
OUT
= 4.75V, 50mV/div
B: I
OUT
= 5mA TO 500mA, 200mA/div
V
IN
= V
OUT
+ 100mV = 4.85V, C
IN
= 10µF
2µs/div
A: MAX1632: V
IN
= 9V, V
OUT
= 5.0V, 20mV/div
B: MAX1857: V
OUT
= 4.75V, I
OUT
= 500mA, 2mV/div
OUT
MAX1632
= IN
MAX1857
B
4.75V
B
A
5.0V
A
SHUTDOWN WAVEFORM
MAX1857 toc08
RST WAVEFORM
MAX1857 toc09
2V
1V
0
6V
4V
2V
0
40µs/div
A: V
SHDN
= 0 TO 2V, 1V/div
B: V
OUT
= 4.75V, 2V/div
R
OUT
= 9.5Ω (500mA)
B
0
0
A
0
A
B
C
20ms/div
A: V
IN
= 0 TO 5.5V, 2V/div
B: V
OUT
= 4.75V, R
OUT
= 95Ω, 2V/div
C: V
RST
, 100kΩ TO OUT, 2V/div
_______________________________________________________________________________________
5
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