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PDF MAX1857 Data sheet ( Hoja de datos )
| Número de pieza | MAX1857 | |
| Descripción | 500mA / Low-Dropout / Ripple-Rejecting LDO in MAX | |
| Fabricantes | Maxim Integrated | |
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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.
Features
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
________________________Applications
Notebook Computers
Cellular and Cordless Telephones
PDAs
Palmtop Computers
Base Stations
USB Hubs
Docking Stations
Ordering Information
PART*
MAX1857EUA47
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
8 µMAX
*Contact factory for other preset output voltages.
Typical Operating Circuit
VIN = +5V
CIN
1µF
NINC
IN
OUT
OUT
MAX1857
ON
SHDN
OFF
RST
SET GND
VOUT = 4.75V
COUT
3.3µF
RRST
100k
TO
µC
TOP VIEW
Pin Configuration
IN 1
IN 2
RST 3
SHDN 4
MAX1857
8 OUT
7 OUT
6 SET
5 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.
1 page  
500mA, Low-Dropout,
Ripple-Rejecting LDO in µMAX
Typical Operating Characteristics (continued)
(VIN = +5.25V, VOUT = 4.75V, SHDN = IN, SET = GND, CIN = 1µF, COUT = 3.3µF, TA = +25°C, unless otherwise noted.)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
80
COUT = 3.3µF
70 IOUT = 50mA
4.80V
LOAD-TRANSIENT RESPONSE
MAX1857 toc05
60
4.75V
A
50 4.70V
40 600mA
30 400mA
B
20 200mA
10 0
0
0.01 0.1 1 10 100 1000
FREQUENCY (kHz)
LOAD-TRANSIENT RESPONSE
NEAR DROPOUT
MAX1857 toc06
10µs/div
A: VOUT = 4.75V, 50mV/div
B: IOUT = 5mA TO 500mA, 200mA/div
VIN = 5.25V, CIN = 10µF
SWITCHING POWER-SUPPLY
RIPPLE REJECTION
MAX1857 toc07
4.80V
4.75V
4.70V
4.65V
400mA
200mA
0
A 5.0V
B 4.75V
A
B
10µs/div
A: VOUT = 4.75V, 50mV/div
B: IOUT = 5mA TO 500mA, 200mA/div
VIN = VOUT + 100mV = 4.85V, CIN = 10µF
SHUTDOWN WAVEFORM
MAX1857 toc08
2V
1V A
0
6V
4V
2V B
0
2µs/div
A: MAX1632: VIN = 9V, VOUT = 5.0V, 20mV/div
B: MAX1857: VOUT = 4.75V, IOUT = 500mA, 2mV/div
OUTMAX1632 = INMAX1857
RST WAVEFORM
MAX1857 toc09
A
0
B
0
C
0
40µs/div
A: VSHDN = 0 TO 2V, 1V/div
B: VOUT = 4.75V, 2V/div
ROUT = 9.5Ω (500mA)
20ms/div
A: VIN = 0 TO 5.5V, 2V/div
B: VOUT = 4.75V, ROUT = 95Ω, 2V/div
C: VRST, 100kΩ TO OUT, 2V/div
_______________________________________________________________________________________ 5
5 Page | ||
| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet MAX1857.PDF ] | |
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