DS1830AS datasheet(3/7 Pages) DALLAS

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D1830/A

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OPERATION — PUSHBUTTON RESET

The DS1830 provides a pushbutton switch for manual reset control. When any of the DS1830/A resets

are not active (low) a reset cycle can be initiated by a pushbutton reset. The pushbutton reset is generated

by pulling the PBRST pin low for at least 1ms. When the push- button is held low all resets are forced

active. The reset will remain active until the pushbutton input is released and then will start a sequenced

time-out based on the condition of the TD input. The Pushbutton input is pulled high through an internal

40k

W pull-up resistor and debounced via internal circuitry. See Figure 2 for an application example and

Figure 3 for the timing diagram.

PUSHBUTTON RESET Figure 2

TIMING DIAGRAM — PUSHBUTTON RESET Figure 3

OPERATION — TIME DELAY SELECT

The DS1830 provides an input to select three time delay characteristics for the reset outputs. The TD

input has 3 states high (VCC), low (ground) and no connect (N.C.). Table 2 details the minimum timing

based on the state of the TD input. If the TD input is connected to ground; RST1 will have a minimum

time delay of 10 ms after VCC is in tolerance. If the TD input is floated; RST1 will have a minimum time

delay of 20 ms after VCC is in tolerance. If the TD input is connected to VCC, RST1 will have a minimum

time delay of 50 ms after VCC is in tolerance. An oscillator and clock chain generate the reset timing with

each time delay based on the same device oscillator. The time delay for RST2 will be 5 times as long as

RST1

and RST3 will be 10 times the duration of RST1 .

TD CONTROL MINIMUM RESET TIMING Table 2

TRST1

TRST2

TRST3

TD = GND

10ms

50ms

100ms

TD = N.C.

20ms

100ms

200ms

TD = VCC

50ms

250ms

500ms

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