Global Mixed-mode Technology Inc.
G680/G681
Microprocessor Reset IC
Features
High
±
2% Voltage Threshold Accuracy
Independently Adjustable High- and Low-
Voltage Thresholds
General Description
The G680/G681 are microprocessor (µP) supervisory
circuits used to monitor the power supplies in µP and
digital systems. High- and Low- voltage thresholds can
be adjusted independently, allowing for wide hystere-
sis. Voltage detection thresholds are accurate to 2%.
These circuits perform a single function: they assert a
reset signal whenever the V
CC
supply voltage declines
below the low-voltage threshold, keeping it asserted
for at least 140ms after V
CC
has risen above the
high-voltage threshold.
The G681L has an open-drain output stage, while the
G680 have push-pull outputs. The G681L’s open-drain
RESET output requires a pull-up resistor that can be
connected to a voltage higher than V
CC
. The G680L
have an active-low RESET output, while the G680H
has an active-high RESET output. The reset com-
parator is designed to ignore fast transients on thresh-
old input.
The IC’s power supply is separate from the detector
inputs, allowing the G680/G681 to be powered from a
down-stream supply. Low supply current (4µA, typical)
makes the G680/G681 ideal for use in portable
equipment. The G680/G681 are available in 5 pin SOT
23-5 packages.
Fully Specified Over Temperature
Available in Three Output Configurations
Push-Pull RESET Output (G680L)
Push-Pull RESET Output (G680H)
Open-Drain RESET Output (G681L)
140ms min Power-On Reset Pulse Width
4µA Supply Current
Power Supply Transient Immunity
5-Pin SOT23-5 Packages
Applications
Computers
Controllers
Intelligent Instruments
Critical µP and µC Power Monitoring
Portable / Battery-Powered Equipment
Automotive
Ordering Information
PART
G680H(L)T1
G681LT1
TEMP. RANGE
-40°C ~ +105°C
-40°C ~ +105°C
PIN-PACKAGE
SOT23-5
SOT23-5
Pin Configuration
Typical Operating Circuit
V
CC
HTH 1
5
Vcc
V
CC
HTH
R
PULL-UP
*
V
CC
GND
2
G680/G681
G680/G681
LTH
RESET
(RESET)
GND
µP
RESET
INPUT
GND
LTH 3
SOT23-5
() is for G680H
4
RESET(RESET)
*G681 ONLY
Ver: 03 Preliminary
Jan 25 2002
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TEL: 886-3-5788833
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Global Mixed-mode Technology Inc.
Absolute Maximum Ratings
Terminal Voltage (with respect to GND)
V
CC
.……………………………..……………-0.3V to +6.0V
Input Voltage (V
LTH
, V
HTH
)…..……….-0.3V to (V
CC
+ 0.3V)
RESET, RESET (push-pull)....…......-0.3V to (V
CC
+ 0.3V)
RESET (open drain)...…........…........…....-0.3V to +6.0V
Input Current, V
CC
............................……................20mA
Output Current, RESET, RESET ..….....................20mA
G680/G681
Continuous Power Dissipation (T
A
= +70°C)
SOT23-5…………………………………………….568mW
Operating Temperature Range …....….-40°C to +105°C
Storage Temperature Range..…...…….-65°C to +150°C
Lead Temperature (soldering, 10s) ...…....…......+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress rat-
ings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of
the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Electrical Characteristics
(V
CC
= full range, T
A
= -40°C to +105°C, unless otherwise noted. Typical values are at T
A
= +25°C, V
CC
= 3.3V (Note 1)
PARAMETER
V
CC
Range
Supply Current (SOT23)
Reset Threshold
Reset Threshold Tempco
V
LTH
to Reset Delay (Note 2)
Reset Active Timeout Period
RESET
(RESET) Output Current Low
RESET
Output Current High
(push-pull G680)
RESET
Open-Drain Output Leakage
Current (G681L)
SYMBOL
I
CC
V
TH
V
CC
<5.5V
CONDITION
MIN
2.5
1.225
TYP MAX UNITS
4
1.25
70
15
420
5.5
7.5
1.272
V
µA
V
ppm/°C
µs
ms
mA
mA
1
µA
V
LTH
= V
TH
to V
TH
– 100mV
120
I
OL
I
OH
V
CC
= 2.5V, V
RESET
(V
RESET
) = 0.5V,
RESET
Asserted or RESET not asserted
V
CC
= 2.5V, V
RESET
(V
RESET
) = 2V,
RESET
not asserted or RESET asserted.
V
HTH
>V
TH
,
RESET
deasserted
8
2
860
Note 1: Production testing done at T
A
= +25°C; limits over temperature guaranteed by design.
Note 2: RESET output is for G680L/G681L; While RESET output is for G680H.
Selector Guide
PART / SUFFIX
G680LT1
G680HT1
G681LT1
OUTPUT TYPE
Push-pull
RESET
Push-pull RESET
Open-Drain
RESET
TOP MARK
680A
680B
681A
Ver: 03 Preliminary
Jan 25 2002
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TEL: 886-3-5788833
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Global Mixed-mode Technology Inc.
Timing Diagram
G680/G681
A
V
HTH
V
BATT
V
LTH
0V
t
RST
V
RESET
V
OH
V
OL
V
RESET
V
OH
V
OL
t
RST
Propagation delays not shown for clarity.
Functional Diagram
V
DD
Low-Voltage Detect
+
LTH
R
High-Voltage Detect
HTH
One Shot
S
Delay
Line
Q
RESET
Q
RESET
+
+
1.24V
Bandgap
Reference
G680/G681
GND
Ver: 03 Preliminary
Jan 25 2002
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TEL: 886-3-5788833
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Global Mixed-mode Technology Inc.
Typical Operating Characteristics
G680/G681
(V
CC
= full range, T
A
= -40°C to +105°C, unless otherwise noted. Typical values are at T
A
= +25°C, V
CC
= 5V
for 463/438/400 versions, V
CC
= 3.3V for 308/293 versions, and V
CC
= 3V for 263 version.)
Supply Current vs.
Temperature
5
4.5
4
Power -Down Reset Delay
vs. Temperature
70
Vcc=5V
Vcc=3.3V
Vcc=2.5V
Power-Down Reset Delay(
μ
S)
60
50
40
30
20
10
V
OD
=V
TH-
VLTH
V
OD
=10mV
Supply Current (uA)
3.5
3
2.5
2
1.5
1
0.5
0
-40
-20
0
20
40
60
80
V
OD
=100mV
V
OD
=200mV
0
-40
-20
0
20
40
60
80
Temperature (°C)
Temperature(°C)
Reset Timeout Period
vs. Temperature
800
700
600
500
400
300
200
100
0
1.002
Normalized Reset Threshold
vs. Temperature
Normalized Reset Threshold (V)
1
0.998
0.996
0.994
0.992
0.99
0.988
0.986
Reset Timeout Period (ms)
V
CC
=5.5V
V
CC
=3V
-40 -30 -20 -10 0
10 20 30 40 50 60 70 80 90
-40 -30 -20 -10 0 10 20 27 30 40 50 60 70 80 90
Temperature (°C)
Temperature (°C)
Ver: 03 Preliminary
Jan 25 2002
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TEL: 886-3-5788833
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Pin Description
PIN
1
2
3
G680/G681
NAME
HTH
GND
LTH
FUNCTION
High-Voltage Theshold (Input): Analog input to a comparator. When the level on this pin initially
rises above V
TH
, the delay generator cycles and the
RESET
remains low or RESET remains high
for a minimum of 140ms.
Ground
Low-Voltage Threshold (Input): Analog input to a comparator. This is the voltage monitor input
assigned to detect a low voltage condition. When the level on this pin falls below V
TH
,
RESET
or
RESET is asserted and the condition is latched until V
HTH
> V
TH
.
Reset (Output): Push-pull output. This output is asserted and latched when V
LTH
<V
TH
, indicating
a low voltage condition. This state remains latched until V
HTH
> V
TH
. The polarity of this signal
(active-high or low) is determined by the part number suffix. See ordering information.
Power Supply (Input): Independent supply input for internal circuitry.
4
5
RESET
(RESET)
V
CC
Detailed Description
A microprocessor’s (µP’s) reset input starts the µP in a
known state. The G681L/G680L/G680H assert reset to
prevent code-execution errors during power-up,
power-down, or brownout conditions. They assert a
reset signal whenever the threshold voltage declines
below V
TH
, keeping it asserted for at least 140ms after
threshold voltage input has risen above the reset
threshold. The G681L uses an open-drain output, and
the G680L/G680H have a push-pull output stage.
Connect a pull-up resistor on the G681L’s RESET out-
put to any supply between 0 and 5.5V.
Battery voltage is monitored by a comparator via a
voltage divider network. The divided voltage is com-
pared to an internal reference voltage. When the volt-
age at the LTH input pin drops below the internal ref-
erence voltage, the output is asserted. At this point,
the voltage at HTH is assumed to be below the refer-
ence voltage.
1400
Applications Information
Negative-Going V
CC
Transients
In addition to issuing a reset to the µP during
power-up, power-down, and brownout conditions, the
G681L/G680H/G680L are relatively immune to short-
duration negative-going V
LTH
transients (glitches).
Figure1. shows typical transient duration vs. reset
comparator overdrive, for which the G681L/G680H/
G680L do not generate a reset pulse. The graph was
generated using a negative-going pulse applied to
V
LTH
, starting 0.1V above the actual reset threshold
and ending below it by the magnitude indicated (reset
comparator overdrive). The graph indicates the maxi-
mum pulse width a negative-going V
LTH
transient can
have without causing a reset pulse. As the magnitude
of the transient increases (goes farther below the reset
threshold), the maximum allowable pulse width de-
creases. Typically, a V
LTH
transient that goes 100mV
below the reset threshold and lasts 7µs or less will not
cause a reset pulse. A 0.1µF bypass capacitor
mounted as close as possible to the V
LTH
pin provides
additional transient immunity.
Programming the Thresholds
The low-voltage threshold is calculated using:
u
s)
Maximun Transient Duration (
1200
1000
800
600
G69__463/438/400
V
BAT (Io)
= V
REF
R1+R2+R3
R2+R3
400
The low-voltage threshold is calculated using:
G69__308/293/263
1
10
100
1000
200
V
BAT (hi)
= V
REF
0
R1+R2+R3
R3
Reset Comparator Overdrive, Vth-Vcc (mV)
where, for both equations:
V
BAT (hi)
= 1.245V
Figure1. Maximum Transient Duration without
Causing a Reset Pulse vs. Reset Com-
parator Overdrive
In order to provide the additional criteria needed to
solve for the resistor values, the resistors can be se-
lected such that they have a given total value, that is,
R1 + R2 + R3 = R
TOTAL
.
Ver: 03 Preliminary
Jan 25 2002
5
TEL: 886-3-5788833
http://www.gmt.com.tw
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