G690H293T26 Просмотр технического описания (PDF) - Global Mixed-mode Technology Inc

Номер в каталоге

Компоненты Описание

Список матч

G690H293T26

Microprocessor Reset IC

Global Mixed-mode Technology Inc 

Global Mixed-mode Technology Inc.

G690/G691

VCC

VCC

G691

RESET

GND

RPULL-UP

VCC

µP

RESET MOTOROLA

INPUT 68HCXX

GND

Figure 3. Interfacing to µPs with Bidirectional Reset

I/O

+3.3V

VCC

G691

RESET

+5.0V

RPULL-UP

VCC

5V SYSTEM

RESET

INPUT

GND

GND

Figure 4. G691L Open-Drain RESET Output Allows

Use with Multiple Supplies

Interfacing to µPs with Bidirectional Reset Pins

Since the RESET output on the G691L is open drain,

this device interfaces easily with µPs that have bidi-

rectional reset pins, such as the Motorola 68HC11.

Connecting the µP supervisor’s RESET output di-

rectly to the microcontroller’s (µC’s) RESET pin with

a single pull-up resistor allows either device to assert

reset (Figure 3).

G691L Open-Drain RESET Output Allows Use with

Multiple Supplies

Generally, the pull-up connected to the G691L will

connect to the supply voltage that is being monitored

at the IC’s VCC pin. However, some systems may use

the open-drain output to level-shift from the monitored

supply to reset circuitry powered by some other supply

(Figure 4). Note that as the G691L’s VCC decreases

below 1V, so does the IC’s ability to sink current at

RESET . Also, with any pull-up, RESET will be pulled

high as VCC decays toward 0. The voltage where this

occurs depends on the pull-up resistor value and the

voltage to which it is connected.

Benefits of Highly Accurate Reset Threshold

Most µP supervisor ICs have reset threshold voltages

between 5% and 10% below the value of nominal

supply voltages. This ensures a reset will not occur

within 5% of the nominal supply, but will occur when

the supply is 10% below nominal.

When using ICs rated at only the nominal supply ±5%,

this leaves a zone of uncertainty where the supply is

between 5% and 10% low, and where the reset may or

may not be asserted.

The G69_ _463/G69_ _308 use highly accurate circuitry

to ensure that reset is asserted close to the 5% limit,

and long before the supply has declined to 10% below

nominal.

Ver: 1.3

Oct 31, 2002

TEL: 886-3-5788833

http://www.gmt.com.tw

9

Share Link: