LM3712/LM3713
Microprocessor Supervisory Circuits with Separate
Watchdog Timer Output, Power Fail Input and Manual
Reset
General Description
The LM3712/LM3713 series of microprocessor supervisory
circuits provide the maximum flexibility for monitoring power
supplies and battery controlled functions in systems without
backup batteries. The LM3712/LM3713 series are available
in a 9-bump micro SMD package.
Built-in features include the following:
Reset: Reset is asserted during power-up, power-down, and
brownout conditions. RESET is guaranteed down to V
CC
of
1.0V.
Manual Reset Input: An input that asserts reset when pulled
low.
Power-Fail Input: A 1.225V threshold detector for power fail
warning, or to monitor a power supply other than V
CC
.
Watchdog Timer: The WDI (Watchdog Input) monitors one of
the P's output lines for activity. If no output transition occurs
during the watchdog timeout period, the watchdog output
(WDO) pulls low.
Features
n
Standard Reset Threshold voltage: 3.08V
n
Custom Reset Threshold voltages: For other voltages
between 2.2V and 5.0V in 10mV increments, contact
National Semiconductor Corp.
n
No external components required
n
Manual-Reset input
n
RESET (LM3712) or RESET (LM3713) outputs
n
Precision supply voltage monitor
n
Factory programmable Reset and Watchdog Timeout
Delays
n
Separate Watchdog output
n
Separate Power Fail comparator
n
Available in micro SMD package for minimum footprint
n
0.5% Reset threshold accuracy at room temperature
n
2% Reset threshold accuracy over temperature
extremes
n
Reset assertion down to 1V V
CC
(RESET option only)
n
28 A V
CC
supply current
Applications
n
Embedded Controllers and Processors
n
Intelligent Instruments
n
Automotive Systems
n
Critical P Power Monitoring
Typical Application
20011903
July 2002
LM3712/LM3713
Microprocessor
Supervisory
Circuits
with
Separate
W
atchdog
T
imer
Output,
Power
Fail
Input
and
Manual
Reset
2002 National Semiconductor Corporation
DS200119
www.national.com
Connection Diagram
Top View
(looking from the coating side)
micro SMD 9 Bump Package
BPA09
20011901
Pin Description
Bump No.
Name
Function
A1
MR
Manual-Reset input. When MR is less than V
MRT
(Manual Reset Threshold)
RESET/RESET is engaged.
B1
V
CC
Power Supply input.
C1
RESET
Reset Logic Output. Pulses low for t
RP
(Reset Timeout Period) when triggered, and stays
low whenever V
CC
is below the reset threshold or when MR is below V
MRT
. It remains low
for t
RP
after either V
CC
rises above the reset threshold, or after MR input rises above
V
MRT
(LM3712 only).
RESET
Reset Logic Output. RESET is the inverse of RESET (LM3713 only).
C2
PFO
Power-Fail Logic Output. When PFI is below V
PFT
PFO goes low; otherwise, PFO remains
high.
C3
WDO
Watchdog Output. If no digital activity is detected on WDI (Watchdog Input) for a period
exceeding t
WD
, this output pulls low.
B3
GND
Ground reference for all signals.
A3
WDI
Watchdog Input Transition Monitor: If no transition activity occurs for a period exceeding
t
WD
(Watchdog Timeout Period), reset is engaged.
A2
PFI
Power-Fail Comparator Input. When PFI is less than V
PFT
(Power-Fail Reset Threshold),
the PFO goes low; otherwise, PFO remains high.
B2
NC
No Connect. Test input used at factory only. Leave floating.
LM3712/LM3713
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Block Diagram
20011905
LM3712/LM3713
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3
Ordering Information
20011904
*For other voltages between 2.2V and 5.0V, please contact National Semiconductor sales office.
LM3712/LM3713
Part Number
Output
Reset Timeout
Period
Watchdog
Timeout Period
Package
Marking
LM3712XQBP-308
totem-pole
200ms
1600ms
%%IC
LM3712XQBPX-308
totem-pole
200ms
1600ms
%%IC
LM3713XQBP-308
totem-pole
200ms
1600ms
%%ID
LM3713XQBPX-308
totem-pole
200ms
1600ms
%%ID
%% is the datecode and will vary with time.
Table Of Functions
Part
Number
Active
Low
Reset
Active
High
Reset
Output
(X = totem-pole)
(Y = open-drain)
Reset
Timeout
Period
Watchdog
Timeout
Period
Manual
Reset
Power Fail
Comparator
LM3712
x
X, Y
*
Customized
Customized
x
x
LM3713
x
X
Customized
Customized
x
x
* = available upon request. Contact National
LM3712/LM3713
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4
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (V
CC
)
-0.3V to 6.0V
All Other Inputs
-0.3V to V
CC
+ 0.3V
ESD Ratings (Note 2)
Human Body Model
Machine Model
1.5kV
150V
Power Dissipation
(Note 3)
Operating Ratings
(Note 1)
Temperature Range
-40C
T
J
85C
LM3712/LM3713 Series Electrical Characteristics
Limits in the standard typeface are for T
J
= 25C and limits in boldface type apply over full operating range. Unless otherwise
specified: V
CC
= +2.2V to 5.5V.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
POWER SUPPLY
V
CC
Operating Voltage
Range: V
CC
LM3712
1.0
5.5
V
LM3713
1.2
5.5
I
CC
V
CC
Supply
Current
All inputs = V
CC
; all outputs floating
28
50
A
RESET THRESHOLD
V
RST
Reset Threshold
V
CC
falling
-0.5
-2
V
RST
+0.5
+2
%
V
CC
falling: T
A
= 0C to 70C
-1.5
+1.5
V
RSTH
Reset Threshold
Hysteresis
0.0032
V
RST
mV
t
RP
Reset Timeout
Period
Reset Timeout Period = E, J, N, S
Reset Timeout Period = F, K, P, T
Reset Timeout Period = G, L, Q, U
Reset Timeout Period = H, M, R, V
1
20
140
1120
1.4
28
200
1600
2
40
280
2240
ms
t
RD
V
CC
to Reset
Delay
V
CC
falling at 1mV/s
20
s
RESET (LM3713)
V
OL
RESET
V
CC
>
2.25V, I
SINK
= 900A
0.3
V
V
CC
>
2.7V, I
SINK
= 1.2mA
0.3
V
CC
>
4.5V, I
SINK
= 3.2mA
0.4
V
OH
RESET
V
CC
>
1.2V, I
SOURCE
= 50A
0.8 V
CC
V
V
CC
>
1.8V, I
SOURCE
= 150A
0.8 V
CC
V
CC
>
2.25V, I
SOURCE
= 300A
0.8 V
CC
V
CC
>
2.7V, I
SOURCE
= 500A
0.8 V
CC
V
CC
>
4.5V, I
SOURCE
= 800A
V
CC
- 1.5V
I
LKG
Output Leakage
Current
V
RESET
= 5.5V
1.0
A
RESET (LM3712)
V
OL
RESET
V
CC
>
1.0V, I
SINK
= 50A
0.3
V
V
CC
>
1.2V, I
SINK
= 100A
0.3
V
CC
>
2.25V, I
SINK
= 900A
0.3
V
CC
>
2.7V, I
SINK
= 1.2mA
0.3
V
CC
>
4.5V, I
SINK
= 3.2mA
0.4
V
OH
RESET
V
CC
>
2.25V, I
SOURCE
= 300A
0.8 V
CC
V
CC
>
2.7V, I
SOURCE
= 500A
0.8 V
CC
V
CC
>
4.5V, I
SOURCE
= 800A
V
CC
- 1.5V
LM3712/LM3713
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