LTC2924 Datasheet, PDF (1/16 Pages) Linear Technology – Quad Power Supply Sequencer

FEATURES
■ _{Fully Sequence 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
■ _{Sequence and Monitor Two or More Supplies}
■ _{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 FAULT 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
Series MOSFET Power Supply Sequencer
1V
3V
5V
5V
EARLY
0.1µF
0.1µF
0.1µF
0.1µF
Q1
Q2
Q3
Q4
SYSTEM
CONTROLLER
10k 10k
150nF
150nF
V_ON = 0.93V
V_OFF = 0.91V
V_ON = 2.79V
V_OFF = 2.73V
0.1µF
V_ON = 4.21V
V_OFF = 3.76V
V_CC
OUT1
IN1
52.3k
45.3k 6.04k
V_ON = 3.32V
V_OFF = 2.80V
1.62k
OUT2
IN2
OUT3
IN3
OUT4
IN4
ON LTC2924
DONE
11.8k 7.68k 1.69k 3.09k
FAULT
TMR HYS/CFG
PGT GND
Q1-Q4: IRL3714S
ALL RESISTORS 1%
49.9k
2924 TA02a
Power-Up Sequence
2V/DIV
10V/DIV
2V/DIV
2V/DIV
5V
3.3V
1V
DONE
ON
TMR
25ms/DIV
2924 TA02b
Power-Down Sequence
2V/DIV
10V/DIV
2V/DIV
2V/DIV
25ms/DIV
5V
3.3V
1V
DONE
ON
TMR
2924 TA02c
2924f
1