Micrel, Inc.

MIC2782

January 2012

8

M9999-010912-A

Functional Description

Design and Product Advantages

The MIC2782 is a dual push-button input reset IC with

extended setup delay times. It is used for generating a

hard reset for microcontrollers, PMICs or load

disconnect switches. The dual manual reset inputs and

long setup delay times help protect against accidental

system resets. The fixed Reset Timeout period allows for

more predictable phone or Tablet operation during

hardware resets. It is used in applications such as smart

phones, tablets, personal navigation devices, MP3

players and Set-Top Boxes (STB).

General Functionality

As shown in Figure 1, if both /MR1 and /MR2 are

the RESET output will be asserted (logic-level low) for a

if either of the /MR1 or /MR2 inputs are de-asserted

high, then the Setup Period timer will be reset. To assert

the RESET output low again, both the /MR1 and /MR2

inputs will have to be asserted low together for the full

duration of the Setup period.

If both /MR1 and /MR2 are asserted low for longer than

be asserted, (logic-level low). ANDOUT will remain

asserted low as long as both the /MR1 and /MR2 inputs

are asserted low. If either the /MR1 or /MR2 are de-

the ANDOUT output will de-assert high.

Figure 1. Manual Reset Function

Keeping both manual reset inputs low for a longer time

does not generate additional RESET output pulses. De-

asserting either manual reset input during the RESET

pulse duration, will not reset the Setup Timer. After the

RESET pin has de-asserted high, both the manual reset

inputs must be held high for more than a Debounce

Time to reset the Setup Timer.

ANDOUT Debounce Time is a de-glitch time, typically

1.5ms, that senses the asserting of both manual reset

inputs low together. A de-glitch time is needed if the

manual reset inputs come from noisy push-button

sources. If either manual reset inputs are asserted (or

de-asserted) for less than a Debounce Time, the

ANDOUT output will not respond.

Dual Manual Reset Inputs (/MR1, /MR2)

The /MR1, /MR2 are active-low manual inputs that have

integrated 65kΩ pull-up resistors to the VDD power

supply. If both inputs are asserted (logic-level low) for a

ANDOUT outputs is independent of the order in which

the /MR1, /MR2 inputs are driven low. The MIC2782

consumes only 2µA when /MR1 and /MR2 manual inputs

are de-asserted (logic-level high) together. Current

consumption is typically 120µA when both manual inputs

are asserted low together and 55µA when only one of

the manual inputs is asserted low while the other manual

input is de-asserted high.

Outputs (RESET and ANDOUT)

The RESET and ANDOUT outputs are simple open-

drain N-channel MOSFET structures that require a pull-

up resistor. For most applications, the pull-up voltage will

the MIC2782. As shown in Figure 2, it is possible to tie

enabling level-shifting of the RESET or ANDOUT

outputs. The pull-up voltage must be limited to 5.5V to

avoid damaging the MIC2782. The pull-up resistor must

be small enough to supply current to the inputs and

leakage paths that are driven by the RESET or ANDOUT

outputs. A recommended value is 100kΩ.

Since the RESET and ANDOUT outputs are open-drain,

several reset sources can be wire-ORed, in parallel, to

allow resets from multiple sources.