No

Second

Pulse

PB1

PB2

RST

TPS3420

TPS3421

TPS3422

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SBVS211A – AUGUST 2012 – REVISED MARCH 2013

PUSH-BUTTON TIMER SELECTION (TS)

Connect the TS pin to either GND or VCC for two different timing options, as shown in Table 1.

Table 1. Push-Button Timer Option Examples

PUSH-BUTTON TIMER

PRODUCT

TS = VCC

TS = GND

RESET PULSE

TPS3420DDRYR/T

12.5 s

7.5 s

N/A

TPS3421EGDRYR/T

0 s

7.5 s

400 ms

TPS3422EGDRYR/T

0 s

7.5 s

400 ms

During normal operation, the TS pin state should not be changed because TS is intended to be permanently

connected to either ground or VCC. The state of the TS pin is checked during power-up and when either PBx

input is high. Therefore, if a different timing option is desired, the state must be changed during power-off, or

when either PBx input is high, in order to avoid false operation.

OUTPUT (RST)

The TPS342x have an open-drain output. A pull-up resistor must be used to hold the line high when the output is

in a high-impedance state (not asserted). By connecting a pull-up resistor to the proper voltage rail, the output

can be connected to other devices at correct interface voltage levels. The TPS342x output can be pulled up to

6.5 V, independent of the device supply voltage. To ensure proper voltage levels, make sure to choose the

The Inputs (PB1, PB2) section describes how the output is asserted or deasserted. See Figure 1 (TPS3420),

Figure 2 (TPS3421) , or Figure 3 (TPS3422) for a timing diagram that describes the relationship between the

PB1 and PB2 inputs and the output. Figure 17 shows the TPS3421 reset timing.

Figure 17. TPS3421 Reset Timing Diagram

Any change in input condition is detected after reset is deasserted. If input PB1 or PB2 has a pulse (low-to-high-

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