Datasheet LTC2951-1, LTC2951-2 (Linear Technology) - 6

LTC2951-1/LTC2951-2
PIN FUNCTIONS (TSOT-23/DFN) VIN (Pin 1/Pin 4):
Power Supply Input: 2.7V to 26.4V. PB power turn-on event, b) KILL is driven low during
PB (Pin 2/Pin 3):
Pushbutton Input. Connecting PB to normal operation, or c) a second valid PB event (power ground through a momentary switch provides on/off turn-off) is detected. This pin can connect directly to a control via the EN/EN pin. An internal 100k pull-up resis- DC/DC converter shutdown pin that provides an internal tor connects to an internal 1.9V bias voltage. The rugged pull-up. Otherwise, a pull-up resistor to an external supply PB input can be pulled up to 26.4V externally without is required. The operating range for this pin is 0V to 10V. consuming extra current.
EN (LTC2951-2, Pin 6/Pin 7):
Open-Drain Enable Output.
KILLT (Pin 3/Pin 2):
Additional, Adjustable KILL Turn-Off This pin is intended to enable system power. EN is asserted Delay Input (t low after a valid PB turn-on event (t KILL, OFF DELAY, ADDITIONAL). A capacitor to DB, ON). EN releases ground provides additional delay time (beyond the internal high if: a) KILL is not driven high within 512ms of the initial default 128ms, t valid PB power turn-on event, b) KILL is driven low during KILL, OFF DELAY) from INT falling to the automatic release of the enable output. The KILL turn-off normal operation, or c) a second valid PB event (power delay feature ensures the release of the enable pin under turn-off) is detected. This pin can connect directly to a system fault conditions, such as the µP not responding DC/DC converter shutdown pin that provides an internal to the LTC2951 interrupt signal (INT low). pull-up. Otherwise, a pull-up resistor to an external supply is required. The operating range of this pin is 0V to 10V.
GND (Pin 4/Pin 1):
Device Ground.
OFFT (Pin 7/Pin 6):
Additional Adjustable Turn-Off Time
INT (Pin 5/Pin 8):
Open-Drain Interrupt Output. After a Input (t pushbutton turn-off event is detected (t OFFT). A capacitor to ground determines the ad- DB, OFF + tOFFT), ditional time (beyond the internal default 32ms, t the LTC2951 interrupts the system (µP) by bringing the DB, OFF) that the PB pin must be held low before initiating a power- INT pin low. Once the system finishes its power-down and down sequence (INT falling). Floating this pin results in a housekeeping tasks, it sets KILL low, which in turn releases default turn-off debounce time of 32ms. the enable output. If at the end of the power-down timer period (tKILL, OFF DELAY + tKILL, OFF DELAY, ADDITIONAL) KILL
KILL (Pin 8/Pin 5):
KILL Input. Forcing KILL low releases is still high, the enable output is released immediately. the enable output. During system turn-on, this pin is INT may optionally be tied to KILL to release the enable blanked by a 512ms internal timer (tKILL, ON BLANK) to output immediately after the turn-off event has been allow the system to pull KILL high. This pin has an accu- detected (INT low). rate 0.6V threshold and can be used as a voltage monitor
EN (LTC2951-1, Pin 6/Pin 7):
Open-Drain Enable Output. input. If unused, connect to a low voltage output supply This pin is intended to enable system power. EN goes high (see Figure 6). after a valid PB turn-on event (tDB, ON). EN goes low if:
Exposed Pad (Pin 9):
Exposed Pad may be left open or a) KILL is not driven high within 512ms of the initial valid connected to device ground. 295112fb 6 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Timing Diagrams Applications Information Typical Applications Package Description Revision History Typical Application Related Parts