![](/html/10/1061/1061b54c924f3c4c4f26fe8f0c812240d9cf810eb85dcc1f4ae8b06876251fc2/bg1.png)
■ GLITCH FREE TRANSITION BETWEEN
INPUT SOURCES
■ INTERNAL LOGIC SELECTS INPUT
SOURCE
■ GATE DRIVE FOR EXTERNAL PMOS
BYPASS SWITCH
■ 5V DETECTOR WITH HYSTERESIS
■ 1% 3.3V REGULATED OUTPUT VOLTAGE
■ 500mA GUARANTEED OUTPUT CURRENT
■ OPERATING TEMPERATURE RANGE
FROM 0°C TO 85°C
■ AVAILABLE IN P
■ PPAK AND SO-8 PACKAGES CAN BE
2
PAK PACKAGE
AVAILABLE ON REQUEST
APPLICATIONS
■ NETWORK INTERFACE CARDS
■ PCMCIA/PCI INTERFACE CARDS
■ DESKTOP COMPUTERS
■ POWER SUPPLY WITH MULTIPLE INPUT
SOURCES
DESCRIPTION
The ST1534A is intended for app lication such as
power managed PCI and network interface cards
(NICs), where operations from 3.3V V AUX supply
SCHEMATIC DIAGRAM
ST1534A
500mA SMART LDO
PPAKP2PAK
SO-8
may be required when the 5V supply has been
shut down.
During regular operation, 3.3V power f or the PCI
card is provided by the internal LDO regulator,
generated from 5V supply. When the 5V V
available, the IC connects thissupply directlyto its
output using an external P-Channel FET. This
ensures an uninterrupted 3. 3V out even if VIN falls
out of specificat ion.
When both supplies are available simultaneously,
the drive p in DR will be pulled high, turning off the
PMOS switch.
The device is available in the popular 5 leads
2
P
PAK and PPA K
AUX
is
+
5V Detect
-
GND
VIN
Reference
+
Error
Amp
-
VIN
Rpull_down
V
OUT
DR
1/15April 2003
![](/html/10/1061/1061b54c924f3c4c4f26fe8f0c812240d9cf810eb85dcc1f4ae8b06876251fc2/bg2.png)
ST1534A
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter² Value Unit
V
V
SHDN
I
T
T
Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition is
not implied.
THERMAL DATA
DC Input Voltage
I
Shutdown Input Voltage
Output Current
O
Storage Temperature Range
stg
Operating Junction Temperature Range
op
-0.3 to 7 V
-0.3 to 7 V
Internally limited mA
-40 to +125 °C
0to+85 °C
Symbol Parameter PPAK
R
thj-case
R
thj-amb
Thermal Resistance Junction-case
Thermal Resistance Junction-ambient
CONNECTION DIAGRAM (top view)
2
PAK
P
PPAK
PIN DESCRIPTION
Pin PPAK/P
1 1 AUX Auxiliary Input port typically 3.3V
2 2 IN Input port typically 5V
3 5, 6, 7, 8 GND Ground
4 3 OUT LDO 3.3V Output Port
5 4 DR Drive Output for external P-Channel MOSFET pass element
2
PAK
Pin SO/8 Symbol Name and Function
2
PAK
P
SO-8 Unit
8320°C/W
100 50 55 °C/W
SO-8
ORDERING INFORMATION
TYPE PPAK (*)
ST1534A ST1534APT ST1534AP2T ST1534AD
(*) PPAK and SO-8 a re availablein Tape & Reel with the suffix"-TR".
2
(#) P
PAKisavailableinTape&Reelwiththesuffix"-R".
2/15
2
PAK (#)
P
SO-8 (*)
![](/html/10/1061/1061b54c924f3c4c4f26fe8f0c812240d9cf810eb85dcc1f4ae8b06876251fc2/bg3.png)
TYPICAL APPLICATION CIRCUIT
ST1534A
3.3V
0.1 µF
5V
4.7 µF 0.1 µF
ELECTRICAL CHARACTERISTICS (T
AUX
IN
GND
=25°C,VI=5V, V
j
DR
OUT
10 µF0.1 µF
=3.3V, IO=10mA, CO=2.2µF,
AUX
Vout=3.3V
unless otherwise spec ified)
Symbol Parameter Test Conditions Min. Typ. Max. Unit
Input Voltage Range 4.5 5 5.5 V
V
I
Input Supply Current VI≥ 4.5V IO= 0mA V
I
IN
I
Auxliary Supply Current VI= 0 V 2.2 mA
AUX
3.3V VOLTAGE REGULATOR BLOCK
V
Output Voltage Tj= 0 to 85 °C 3.18 3.3 3.42 V
O
∆V
∆V
Line Regulation VI= 4.5 to 5.5V 0.04 0.5 %
O
Load Regulation IO= 0 to 500mA 0.1 1 %
O
Dropout Voltage IO= 500 mA Tj= 0 to 85 °C 1.15 V
V
d
Output Current Limit Tj=0to85°C 550 mA
I
O
5V DETECT BLOCK
V
V
Low Threshold Voltage VIfalling, IO= 500 mA Tj= 0 to 85 °C 4.15 4.3 V
THL
Hysteresis 70 200 mV
HYST
DRIVE OUTPUT BLOCK
V
Note 1: Guaranteed by design
Note 2: See timing diagram
Drive Output Voltage VI= 4.5 to 5.5V IDR=200µA 3.6 VIN-0.8 V
DR
Drive Current Sinking: VI= 4.15V VDR= 1V 7 20 mA
I
DR
Drive High Delay (Note 1
t
DH
and 2)
Drive Low Delay (Note 1
t
DL
and 2)
≥4.5V IO= 0mA V
V
I
< 4.1V IO= 0mA V
V
I
< 4.1V IO= 0mA V
V
I
V
= 5V 200 µA
I
< 4.15V IDR=200µA 100 200 mV
V
I
Sourcing: V
= 4.5V VI-VDR= 2V 7 25 mA
I
CDR= 1.2nF,VINramping up, measured
from V
I=VTH(H)
=0to85°C
T
j
to VDR= 3.3V
CDR= 1.2nF,VINramping down, measured
from V
I=VTH(L)
T
=0to85°C
j
to VDR= 200mV
=0V 11 mA
AUX
= 3.3V 11 mA
AUX
=0V 2 mA
AUX
= 3.3V 2 mA
AUX
25µs
36µs
3/15
![](/html/10/1061/1061b54c924f3c4c4f26fe8f0c812240d9cf810eb85dcc1f4ae8b06876251fc2/bg4.png)
ST1534A
5V DETECT THRESHOLDS
VINrise and fall times (10% to 90%) to be > 100µs
TIMING DIAGRAM
VINrise and fall times (10% to 90%) to be > 100µs
4/15
![](/html/10/1061/1061b54c924f3c4c4f26fe8f0c812240d9cf810eb85dcc1f4ae8b06876251fc2/bg5.png)
TYPICAL CHARACTERISTICS (unless otherwise specified Tj=25°C)
ST1534A
Figure1 : Supply Currentvs Temperature
Figure2 : Aux Current vs Temperature
Figure4 : Aux Current vs Temperature
Figure5 : Drive Output Voltage vs Tem perature
Figure3 : Drive Current vs Temperature
Figure6 : Drive Current vs V
IN-VDR
5/15