MIC2779 Micrel Semiconductor, MIC2779 Datasheet - Page 4

• Manufacturer Part Number: MIC2779
• Description: Voltage Monitor with Adjustable Hysteresis Preliminary Information
• Manufacturer: Micrel Semiconductor

MIC2779
Functional Diagram
Functional Description
The MIC2779 monitors the voltage of a battery and detects
when it is discharged below a programmed level. Upon being
replaced, or being recharged above a second higher pro-
grammed trip point, the output remains low (MIC2779L) or
high (MIC2779H) for a minimum of 140ms and then sends a
reset signal to a microprocessor or other downstream com-
ponent. See “Timing Diagram.”
/RST, RST Low Output
The output is a push-pull logic signal which is asserted when
the MIC2779 detects a low input voltage. The MIC2779L’s
/RST output is active-low; the MIC2779H’s RST output is
active-high.
MIC2779
V
V
LO
V
HI
BATT
HTH
LTH
* Pinout and polarity vary by device type.
See ordering information table.
GND
V
DD
1.24V
Bandgap
Reference
High-Voltage
Low-Voltage
Detect
Detect
Delay
Line
4
Trip Points
Battery voltage is monitored by a comparator via a voltage
divider network. The divided voltage is compared to an
internal reference voltage. When the voltage at the LTH input
pin drops below the internal reference voltage, the output is
asserted. At this point, the voltage at HTH is assumed to be
below the reference voltage.
Delay
At power-on or when the battery is replaced or recharged,
and the voltage at HTH exceeds the reference voltage, the
output is deasserted after a minimum delay of 140ms.
One Shot
R
S
Q
Q
MIC2779
/RST*
RST*
June 2000
Micrel