MIC2788 데이터 시트보기 (PDF) - Micrel

부품명

상세내역

제조사

MIC2788

Push-Button Reset IC

Micrel 

Micrel, Inc.

MIC2788/MIC2789

Application Information

Design and Product Advantages

The dual reset programmability of the MIC2788/

MIC2789 allows for already existing manual push

buttons to be used to generate a hardware reset based

on pre-programmed timing requirements. This ability to

increase the functionality of already existing buttons,

allows for cost reduction and more robust phone

designs. The dual reset delay time allows for significant

protection against accidental resets due to its long time

duration and dual push button requirement. The fixed

reset timeout delay allows for more predictable phone

operation during hardware resets. The tri-state option

provides an easy to use way to select between three

reset delay time options with no additional external

components required.

Supply Bypass Capacitor

A 0.1µF input bypass capacitor must be placed from VIN

(Pin 8) to GND (Pin 2).

Programmable Delay Pin (PDY)

The MIC2788/MIC2789 has a programmable dual reset

delay time, tSETUP, that is set via a tri-state logic

configuration. The PDY pin is intended to be connected

to the VIN supply voltage, ground or left floating.

PDY Configuration

OPEN

GND

VIN

tSETUP

2s

4s

6s

Dual Manual Reset Inputs (/MR0, /MR1)

The /MR0, /MR1 input pins have integrated pull-up

resistors for the MIC2788 but require external pull-up

resistors for the MIC2789. A recommended value is

100kΩ to keep the current consumption low when the

push-button switches are pressed. The behavior of the

reset outputs is independent of the order in which the

/MR0, /MR1 inputs are driven low. If both inputs are low

for a setup delay time, only one reset pulse, of width

tRESET, is generated. Keeping both inputs low for a

longer time does not generate additional reset output

pulses.

Reset Outputs (/RST and RSTP)

The /RST output is a simple open-drain N-channel

MOSFET structure that requires a pull-up resistor. For

most applications, the pull-up voltage will be the same

as the power supply that supplies VIN to the

MIC2788/MIC2789. As shown in Figure 1, it is possible

to tie this resistor to some other voltage, other than VIN,

thus enabling level-shifting of the /RST output. The pull-

up voltage must be limited to 5.5V or less to avoid

damage to the MIC2788/MIC2789. The pull-up resistor

must be small enough to supply current to the inputs and

leakage paths that are driven by the /RST output. A

recommended value is 100kΩ. Leave floating if the /RST

pin is unused.

The RSTP pin is a push-pull output that is driven to VIN.

It cannot be level-shifted to another voltage. It is an

inverted signal of /RST.

Figure 1. MIC2788/MIC2789 Used in Multiple Supply

System

The reset outputs /RST and RSTP are asserted when

the dual reset delay time, tSETUP, is exceeded while the

/MR0, /MR1 pins are driven low. Both the reset outputs

remain asserted for a factory-programmed reset timeout

delay time tRESET. Two options are available with 140ms

or 240ms minimum tRESET duration. The /RST pin is

driven active low while the RSTP pin is driven active

high for the tRESET duration. The reset outputs are de-

asserted for VIN < 1.6V.

Figure 2. Manual Reset Function

October 2011

10

M9999-102711-A

Share Link: