ISL88021 데이터 시트보기 (PDF) - Renesas Electronics

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ISL88021

Triple Voltage Monitor with Adjustable Power-On-Reset and Undervoltage/Overvoltage Monitoring Capability

Renesas Electronics 

ISL88021, ISL88022

Manual Reset

The manual reset input (MR) allows the user to trigger a reset by

using a push-button switch or by signaling that pin low. The MR

input is an active low debounced input. By connecting a push-

button directly from MR to ground, the designer adds manual

system reset capability. Reset is asserted if the MR pin is pulled

low to less than 100mV for 1µs or longer while the push-button is

closed or a reset is signaled. After MR is released, the reset

outputs remain asserted for tPOR. MR input has an internal 20k

pull up resistor provided.

Figure 3 illustrates a typical application diagram for either IC

showing both reset outputs being used along with both a manual

and signalled reset configuration. The VDD and V2MON

thresholds are preset whereas the V3MON is capable of UV

(ISL88021) or OV (ISL88022) monitoring of a voltage greater than

or less than 0.6V, respectively.

TO DISPLAY

3.3V - 5V

1.8V - 3.3V

VDD

RST

RST

V2MON

MR

ISL88021

ISL88022

TO µP

PB

RESET

SIGNAL

VMON > 0.6V

V3MON

CPOR

GND

ISL88021IU8HFZ

ISL88022IU8HFZ

FIGURE 3. TYPICAL APPLICATION DIAGRAM

Application Considerations

Follow good decoupling practices to prevent transients from

causing unwanted reset signaling due to switching noises and

short duration droops.

When using the CPOR pin, reduce layout stray capacitance on

this pin to minimize effect on tPOR timing. If no PCB CPOR pad

is patterned, the tPOR can be 160ms.

Using the ISL88021_22EVAL1 Platform

The ISL88021_22EVAL1 board is designed to provide both

immediate functional assessment and flexibility to the user. Both

ICs are the ‘HF’ variant having a VDD Vth of 4.64V, a V2MON

Vth of 3.09V and V3MON Vth of 0.6V. The top IC position is the

ISL88021 and is configured to monitor for undervoltage (UV)

compliance of a 5V, 3.3V and a 2.5V and signaling the RESET

and RESET outputs. The bottom position is the ISL88022

variant, which is configured to measure a 3.3V overvoltage

(OV) in addition to UV on both the 5V and 3.3V supplies.

RESET and RESET is asserted for at least tPOR when these

voltage go out of range. In both cases V3MON interfaces with

the monitored supply via a simple resistor divider for comparison

to the internal 0.6V reference. A Manual Reset (MR) input is

provided on both ICs and is invoked by pulling this input LOW.

FN8226 Rev 1.00

September 18, 2006

FIGURE 4. ISL88021_22EVAL1 SCHEMATIC AND PHOTO

MONITORED VOLTAGE RISING AND FALLING RAMP

THROUGH THE PROGRAMMED UV AND OV THRESHOLDS

RESET# RESPONDING TO

MONITORED VOLTAGE. CPOR

PIN IS OPEN, tPOR = 150ms

FIGURE 5. ISL88022EVAL1 3.3V UV AND OV DETECTION

Page 5 of 8

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