LTC2924

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


Application

Sequenced Power Supplies for ASICs with Multiple I/O and Core Voltages
Latch-Up Prevention in Systems with Multiple Power Supplies


Pinout




Specifications

Supply Voltage (VCC) ...............................  0.3V to 6.5V
Input Voltages
ON, IN1-IN4............................... ..... 0.3V to VCC + 0.3V
PGT, TMR, HYS/CFG ........................  0.3V to VCC + 0.3V
Open-Drain Output Voltages
FAULT, DONE .................................. 0.3V to VCC + 0.3V
Output Voltages
(OUT1-OUT4) (Note 5) ................... 0.3V to VCC + 4.5V
Operating Temperature Range
LTC2924C .................................................. 0°C to 70°C
LTC2924I .............................................. 40°C to 85°C
Storage Temperature Range ............. 65°C to 150°C
Lead Temperature (Soldering, 10 sec) ................  300°C


Description

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 precision 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.