Ver: 03 Preliminary
Jan 25 2002
TEL: 886-3-5788833
http://www.gmt.com.tw
1
G680/G681
Global Mixed-mode Technology Inc.
Microprocessor Reset IC
Features
High
2% Voltage Threshold Accuracy
Independently Adjustable High- and Low-
Voltage Thresholds
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
4A Supply Current
Power Supply Transient Immunity
5-Pin SOT23-5 Packages
Applications
Computers
Controllers
Intelligent Instruments
Critical P and C Power Monitoring
Portable / Battery-Powered Equipment
Automotive
General Description
The G680/G681 are microprocessor (P) supervisory
circuits used to monitor the power supplies in P 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 (4A, typical)
makes the G680/G681 ideal for use in portable
equipment. The G680/G681 are available in 5 pin SOT
23-5 packages.
Ordering Information
PART TEMP.
RANGE PIN-PACKAGE
G680H(L)T1
-40C ~ +105C
SOT23-5
G681LT1
-40C ~ +105C
SOT23-5
Pin Configuration Typical Operating Circuit
Vcc
RESET(RESET)
SOT23-5
5
4
1
HTH
2
3
GND
LTH
G680/G681
() is for G680H
RESET
INPUT
GND
P
V
CC
RESET
(RESET)
GND
G680/G681
V
CC
R
PULL-UP
V
CC
*
*G681 ONLY
HTH
LTH
Vcc
RESET(RESET)
SOT23-5
5
4
1
HTH
2
3
GND
LTH
G680/G681
() is for G680H
Vcc
RESET(RESET)
SOT23-5
5
4
1
HTH
2
3
GND
LTH
G680/G681
() is for G680H
RESET
INPUT
GND
P
V
CC
RESET
(RESET)
GND
G680/G681
V
CC
R
PULL-UP
V
CC
*
*G681 ONLY
HTH
LTH
RESET
INPUT
GND
P
V
CC
RESET
(RESET)
GND
G680/G681
V
CC
R
PULL-UP
V
CC
*
*G681 ONLY
HTH
LTH
Ver: 03 Preliminary
Jan 25 2002
TEL: 886-3-5788833
http://www.gmt.com.tw
2
G680/G681
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
Continuous Power Dissipation (T
A
= +70C)
SOT23-5....................................................568mW
Operating Temperature Range ...........-40C to +105C
Storage Temperature Range...............-65C to +150C
Lead Temperature (soldering, 10s) ...................+300C
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
= -40C to +105C, unless otherwise noted. Typical values are at T
A
= +25C, V
CC
= 3.3V (Note 1)
PARAMETER SYMBOL CONDITION
MIN
TYP
MAX
UNITS
V
CC
Range
2.5
5.5
V
Supply Current (SOT23)
I
CC
V
CC
<5.5V
4 7.5 A
Reset Threshold
V
TH
1.225 1.25 1.272
V
Reset Threshold Tempco
70
ppm/C
V
LTH
to Reset Delay (Note 2)
V
LTH
= V
TH
to
V
TH
100mV
15
s
Reset Active Timeout Period
120 420 860 ms
RESET
(RESET) Output Current Low
I
OL
V
CC
= 2.5V, V
RESET
(V
RESET
) = 0.5V, RESET
Asserted or RESET not asserted
8 mA
RESET
Output Current High
(push-pull G680)
I
OH
V
CC
= 2.5V, V
RESET
(V
RESET
)
= 2V, RESET
not asserted or RESET asserted.
2 mA
RESET
Open-Drain Output Leakage
Current (G681L)
V
HTH
>V
TH
, RESET deasserted
1 A
Note 1: Production testing done at T
A
= +25C; limits over temperature guaranteed by design.
Note 2: RESET output is for G680L/G681L; While RESET output is for G680H.
Selector Guide
PART / SUFFIX
OUTPUT TYPE
TOP MARK
G680LT1
Push-pull
RESET
680A
G680HT1 Push-pull
RESET
680B
G681LT1
Open-Drain
RESET
681A
Ver: 03 Preliminary
Jan 25 2002
TEL: 886-3-5788833
http://www.gmt.com.tw
3
G680/G681
Global Mixed-mode Technology Inc.
Timing Diagram
Functional Diagram
V
BATT
V
RESET
V
RESET
Propagation delays not shown for clarity.
V
HTH
V
LTH
0V
t
RST
t
RST
A
V
OH
V
OL
V
OH
V
OL
V
BATT
V
RESET
V
RESET
Propagation delays not shown for clarity.
V
HTH
V
LTH
0V
t
RST
t
RST
A
V
OH
V
OL
V
OH
V
OL
+
+
High-Voltage Detect
Delay
Line
R Q
S
Q
One Shot
Low-Voltage Detect
+
1.24V
Bandgap
Reference
GND
G680/G681
RESET
RESET
V
DD
LTH
HTH
+
+
High-Voltage Detect
Delay
Line
R Q
S
Q
One Shot
Low-Voltage Detect
+
1.24V
Bandgap
Reference
GND
G680/G681
RESET
RESET
V
DD
LTH
HTH
Ver: 03 Preliminary
Jan 25 2002
TEL: 886-3-5788833
http://www.gmt.com.tw
4
G680/G681
Global Mixed-mode Technology Inc.
Typical Operating Characteristics
(V
CC
= full range, T
A
= -40C to +105C, unless otherwise noted. Typical values are at T
A
= +25C, V
CC
= 5V
for 463/438/400 versions, V
CC
= 3.3V for 308/293 versions, and V
CC
= 3V for 263 version.)
Power -Down Reset Delay
vs. Temperature
0
10
20
30
40
50
60
70
-40
-20
0
20
40
60
80
Temperature(C)
Power-Down Reset Delay(
S)
V
OD
=10mV
V
OD
=V
TH-
VLTH
V
OD
=100mV
V
OD
=200mV
Supply Current vs.
Temperature
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
-40
-20
0
20
40
60
80
Temperature (C)
Supply Current (uA)
Vcc=5V
Vcc=3.3V
Vcc=2.5V
Normalized Reset Threshold
vs. Temperature
0.986
0.988
0.99
0.992
0.994
0.996
0.998
1
1.002
-40 -30 -20 -10 0 10 20 27 30 40 50 60 70 80 90
Temperature (C)
Normalized Reset Threshold (V)
Reset Timeout Period
vs. Temperature
0
100
200
300
400
500
600
700
800
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90
Temperature (C)
Reset Timeout Period (ms)
V
CC
=5.5V
V
CC
=3V
Ver: 03 Preliminary
Jan 25 2002
TEL: 886-3-5788833
http://www.gmt.com.tw
5
G680/G681
Global Mixed-mode Technology Inc.
Pin Description
PIN NAME
FUNCTION
1 HTH
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.
2 GND
Ground
3 LTH
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
.
4
RESET
(RESET)
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.
5 V
CC
Power Supply (Input): Independent supply input for internal circuitry.
Detailed Description
A microprocessor's (P's) reset input starts the P 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.
Figure1. Maximum Transient Duration without
Causing a Reset Pulse vs. Reset Com-
parator Overdrive
Applications Information
Negative-Going V
CC
Transients
In addition to issuing a reset to the P 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 7s or less will not
cause a reset pulse. A 0.1F 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:
R1+R2+R3
V
BAT (Io)
= V
REF
R2+R3
The low-voltage threshold is calculated using:
R1+R2+R3
V
BAT (hi)
= V
REF
R3
where, for both equations:
V
BAT (hi)
= 1.245V
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
.
0
200
400
600
800
1000
1200
1400
1
10
100
1000
Reset Comparator Overdrive, Vth-Vcc (mV)
M
a
x
i
m
un T
r
ans
i
ent
D
u
r
a
t
i
on (
u
s)
G69__308/293/263
G69__463/438/400
Ver: 03 Preliminary
Jan 25 2002
TEL: 886-3-5788833
http://www.gmt.com.tw
6
G680/G681
Global Mixed-mode Technology Inc.
A value such as 1M
for R
TOTAL
is a reasonable value
because it draws minimum battery current but has no
measurable effect on accuracy.
When working with large resistors, a small amount of
leakage current can cause voltage offsets that
degrade system accuracy.
The maximum recommended total resistance from
V
BAT
to ground is 3M
.
Figure 2. Example Circuit
Once the desired trip points are determined, set the
V
BAT(hi)
threshold first.
For example, use a total of 1M = R1 + R2 + R3. For a
typical single-cell lithium ion battery, 3.6V is a good
"high threshold" because at 3.6V the battery is moder-
ately charged. Solving for R3:
1M
V
BAT (hi)
= 1.245
R3
R3 = 344k
Once R3 is determined, the equation for V
BAT (lo)
can
be used to determine R2. A single lithium-ion cell
should not be discharged below 2.5V. Many applica-
tions limit the drain to 3.1V. Using 3.1V for the V
BAT (lo)
threshold allows calculation of the two remaining re-
sistor values.
1M
V
BAT (lo)
=3.1V = 1.245
R2+344k
R2 = 56k
R1 = 1M
- R2 - R3
R 1=600k
The accuracy of the resistors can be chosen based
upon the accuracy required by the system.
Figure 3. Interfacing to Ps with Bidirectional Re-
set I/O
Interfacing to Ps with Bidirectional Reset Pins
Since the RESET output on the G681L is open drain,
this device interfaces easily with Ps that have bidi-
rectional reset pins, such as the Motorola 68HC11.
Connecting the P supervisor's RESET output di-
rectly to the microcontroller's (C's) RESET pin with
a single pull-up resistor allows either device to assert
reset (Figure 3).
.
V
B A TT
V C C
L T H
H T H
R E S E T
R E S E T
R 1
R 2
R 3
6 0 4 k
1 %
5 6 k
1 %
3 4 0 k
1 %
G 68 0/G 681
V
B A TT
V C C
L T H
H T H
R E S E T
R E S E T
R 1
R 2
R 3
6 0 4 k
1 %
5 6 k
1 %
3 4 0 k
1 %
G 68 0/G 681
RESET
INPUT
GND
P
V
CC
RESET
GND
G681
V
CC
V
CC
MOTOROLA
68HCXX
R
PULL-UP
RESET
INPUT
GND
P
V
CC
RESET
GND
G681
V
CC
V
CC
MOTOROLA
68HCXX
R
PULL-UP
Ver: 03 Preliminary
Jan 25 2002
TEL: 886-3-5788833
http://www.gmt.com.tw
7
G680/G681
Global Mixed-mode Technology Inc.
Package Information
Note:
1. Package body sizes exclude mold flash protrusions or gate burrs
2. Tolerance 0.1000 mm (4mil) unless otherwise specified
3. Coplanarity: 0.1000mm
4.
Dimension L is measured in gage plane
DIMENSIONS IN MILLIMETERS
SYMBOLS
MIN NOM MAX
A 1.00 1.10 1.30
A1 0.00 ----- 0.10
A2 0.70 0.80 0.90
b 0.35 0.40
0.50
C 0.10 0.15 0.25
D 2.70 2.90 3.10
E 1.40 1.60 1.80
e -----
1.90(TYP)
-----
e1 ----- 0.95 -----
H 2.60 2.80 3.00
L 0.37 ------ -----
1
1 5 9
Taping Specification
E
e
D
H
1
L
C
b
A2
A1
A
e1
E
e
D
H
1
L
C
b
A2
A1
A
e1
Feed Direction
SOT23-5 Package Orientation
Feed Direction
SOT23-5 Package Orientation
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