LTC2924 Datasheet, PDF (1/20 Pages) Linear Technology – Quad Power Supply Sequencer

FEATURES
■ _{Fully Sequence and Monitor Four Supplies}
– Six with Minimal External Circuitry
■ _{Cascadable for Additional Supplies}
■ _{Power Off in Reverse Order or Simultaneously}
■ _{Charge Pump Drives External MOSFETs}
■ _{Drives Power Supply Shutdown Pins with No}
External Pull-Up Resistors
■ _{10µA Output Current Allows Soft-Starting of Supplies}
■ _{Done Indicator for Both Power On and Power Off}
■ _{Adjustable Time Delay Between Power Supplies}
■ _{Power Good Timer}
■ _{Power Supply Voltage Monitoring and Power}
Sequence Error Detection and Reporting
■ _{Available in a 16-Lead Narrow SSOP Package}
U
APPLICATIO S
■ _{Sequenced Power Supplies for ASICs with Multiple}
I/O and Core Voltages
■ _{Latch-Up Prevention in Systems with Multiple Power}
Supplies
LTC2924
Quad Power Supply
Sequencer
DESCRIPTIO
The LTC^®2924 is a power supply sequencer designed for
use with external N-channel MOSFETs or power supplies
with shutdown pins. Four power supplies can be fully
sequenced by a single LTC2924 and up to five supplies
can be sequenced to a sixth master supply. The LTC2924
requires a minimum of external components, using only
two feedback resistors per sequenced power supply and
a single resistor to set hysteresis.
An internally regulated charge pump provides gate drive
voltages for external logic and sub-logic-level MOSFETs.
Adding a single capacitor enables an adjustable time delay
between power supplies during both Power On and Power
Off sequencing. A second capacitor can be added to enable
a power good timer for detecting the failure of any power
supply to turn on within the selected time. Errors in power
supply sequencing and the control input are detected and
reported at the FAULT output. The LTC2924 features pre-
cision input comparators which can provide 1% accuracy
in monitoring power supply voltages.
Multiple LTC2924s may be easily cascaded to sequence
a virtually unlimited number of power supplies.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
3.3V
SHDN
Q2
1V
5V
5V
SHDN
Q1
3V
5V EARLY
10k 10k
SYSTEM
CONTROLLER
150nF
150nF
V_ON = 2.64V
V_OFF = 1.98V
V_ON = 0.93V
V_OFF = 0.915V
0.1µF
V_ON = 3.97V
V_OFF = 2.97V
V_CC
OUT1
IN1
OUT2
IN2
OUT3
IN3
OUT4
IN4
ON LTC2924
DONE
FAULT
TMR HYS/CFG
PGT GND
6.04k
100k
1.62k
V_ON = 2.79V
V_OFF = 2.73V
66.5k
1.69k 18.2k 3.09k 20k
Q1-Q4: IRL3714S
ALL RESISTORS 1%
49.9k
2924 TA01a
Power-Up Sequence
5V
2V/DIV
3.3V
3V
1V
5V/DIV
2V/DIV
5V/DIV
DONE
TMR
ON
10ms/DIV
2924 TA01b
Power-Down Sequence
5V
3.3V
2V/DIV
3V
1V
5V/DIV
2V/DIV
5V/DIV
10ms/DIV
DONE
TMR
ON
2924 TA01c
2924fa
1