LM3710/LM3711
Microprocessor Supervisory Circuits with Power Fail
Input, Low Line Output, Manual Reset and Watchdog
Timer
General Description
The LM3710/LM3711 series of microprocessor supervisory
circuits provide the maximum flexibility for monitoring power
supplies and battery controlled functions in systems without
backup batteries. The LM3710/LM3711 series are available
in MSOP-10 and 9-bump micro SMD packages.
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
.
Low Line Output: This early power failure warning indicator
goes low when the supply voltage drops to a value which is
2% higher than the reset threshold voltage.
Watchdog Timer: The WDI (Watchdog Input) monitors one of
the µP's output lines for activity. If no output transition occurs
during the watchdog timeout period, reset is activated.
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 (LM3710) or RESET (LM3711) outputs
n
Precision supply voltage monitor
n
Factory programmable Reset and Watchdog Timeout
Delays
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 µA V
CC
supply current
Applications
n
Embedded Controllers and Processors
n
Intelligent Instruments
n
Automotive Systems
n
Critical µP Power Monitoring
Typical Application
20011803
June 2002
LM3710/LM371
1
Microprocessor
Supervisory
Circuits
with
Power
Fail
Input,
Low
Line
Output,
Manual
Reset
and
W
atchdog
T
imer
© 2002 National Semiconductor Corporation
DS200118
www.national.com
Connection Diagram
MSOP-10
Top View
(looking from the coating side)
micro SMD 9 Bump Package
BPA09
20011802
20011801
Pin Descriptions
Pin No.
Name
Function
micro
SMD
MSOP
A1
2
MR
Manual-Reset input. When MR is less than V
MRT
(Manual Reset Threshold)
RESET/RESET is engaged.
B1
1
V
CC
Power Supply input.
C1
10
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
(LM3710 only).
RESET
Reset Logic Output. RESET is the inverse of RESET (LM3711 only).
C2
8
PFO
Power-Fail Logic Output. When PFI is below V
PFT
, PFO goes low; otherwise, PFO
remains high.
C3
7
LLO
Low-Line Logic Output. Early Power-Fail warning output. Low when V
CC
falls below V
LLOT
(Low-Line Output Threshold). This output can be used to generate an NMI (Non-Maskable
Interrupt) to provide an early warning of imminent power-failure.
B3
5
GND
Ground reference for all signals.
A3
4
WDI
Watchdog Input Transition Monitor: If no transition activity occurs for a period exceeding
t
WD
(Watchdog Timeout Period), reset is engaged.
A2
3
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
6, 9
NC
No Connect. Test input used at factory only. Leave floating.
LM3710/LM371
1
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2
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
-40°C
T
J
85°C
LM3710/LM3711 Series Electrical Characteristics
Limits in the standard typeface are for T
J
= 25°C 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
LM3710
1.0
5.5
V
LM3711
1.2
5.5
I
CC
V
CC
Supply
Current
All inputs = V
CC
; all outputs floating
28
50
µA
RESET THRESHOLD
V
RST
Reset Threshold
V
CC
falling
-0.5
-2
V
RST
+0.5
+2
%
V
CC
falling: T
A
= 0°C to 70°C
-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/µs
20
µs
RESET (LM3711)
V
OL
RESET
V
CC
>
2.25V, I
SINK
= 900µA
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
= 50µA
0.8 V
CC
V
V
CC
>
1.8V, I
SOURCE
= 150µA
0.8 V
CC
V
CC
>
2.25V, I
SOURCE
= 300µA
0.8 V
CC
V
CC
>
2.7V, I
SOURCE
= 500µA
0.8 V
CC
V
CC
>
4.5V, I
SOURCE
= 800µA
V
CC
- 1.5V
I
LKG
Output Leakage
Current
V
RESET
= 5.5V
1.0
µA
RESET (LM3710)
V
OL
RESET
V
CC
>
1.0V, I
SINK
= 50µA
0.3
V
V
CC
>
1.2V, I
SINK
= 100µA
0.3
V
CC
>
2.25V, I
SINK
= 900µA
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
= 300µA
0.8 V
CC
V
CC
>
2.7V, I
SOURCE
= 500µA
0.8 V
CC
V
CC
>
4.5V, I
SOURCE
= 800µA
V
CC
- 1.5V
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