ISL88021 View Datasheet(PDF) - Intersil
Part Name
Description
MFG CO.
ISL88021 Datasheet PDF : 7 Pages
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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 20kΩ 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
V2MON
RST
RST
MR
ISL88021
ISL88022
TO µP
RESET
PB 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.
5
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
FN8226.1
September 18, 2006
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