G696H263TOUF datasheet(9/11 Pages) GMT

9 / 11 page

Ver: 1.8

May 10, 2006

TEL: 886-3-5788833

http://www.gmt.com.tw

G696/G697

Global Mixed-mode Technology Inc.

Interfacing to µPs with Bidirectional Reset Pins

Since the RESET output on the G697L is open drain,

this device interfaces easily with µPs that have bidirec-

tional reset pins, such as the Motorola 68HC11. Con-

necting the µP supervisor’s RESET output directly to

the microcontroller’s (µC’s) RESET pin with a single

pull-up resistor allows either device to assert reset

(Figure 5).

G697L Open-Drain RESET Output Allows Use with

Multiple Supplies

Generally, the pull-up connected to the G697L 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 6). Note that as the G697L’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.

G696H263TOUF Datasheet(PDF) 9 Page - Global Mixed-mode Technology Inc