Datasheet G680LT1, G680HT1, G681LT1 Datasheet (GMT)

Ver: 1.1

Jun 07, 2002

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1

G680/G681

Global Mixed-mode Technology Inc.

Microprocessor Reset IC

Features



High ±±±±2% Voltage Threshold Accuracy



Independently Adjustable High- and Low­Voltage 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



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

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 hystere­sis. 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 com­parator is designed to ignore fast transients on thresh­old 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.

Ordering Information

PART TEMP. RANGE PIN-PACKAGE

G680H(L)T1 -40°C ~ +105°C SOT23-5

G681LT1 -40°C ~ +105°C 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

µP

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

µP

V

CC

RESET

(RESET)

GND

G680/G681

V

CC

R

PULL-UP

V

CC

*

*G681 ONLY

HTH

LTH

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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 (VCC + 0.3V)

RESET,

RESET (push-pull)....…......-0.3V to (VCC + 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

= +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

(VCC = full range, TA = -40°C to +105°C, unless otherwise noted. Typical values are at TA = +25°C, VCC = 3.3V (Note 1)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS

VCC Range 2.5 5.5 V
Supply Current (SOT23)

I

CC

V

CC

<5.5V

4 7.5

µA
Reset Threshold VTH 1.23 1.25 1.29 V
Reset Threshold Tempco 70 ppm/°C
V

LTH

to Reset Delay (Note 2) V

LTH

= VTH to VTH – 100mV 15 µs

VCC = 2.5V 80 250 550

Reset Active Timeout Period

V

CC

= 5.5V 500

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

Note 1: Production testing done at TA = +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 OUTPUT TYPE

TOP MARK

G680LT1

Push-pull

RESET

680Ax

G680HT1 Push-pull RESET 680Bx

G681LT1

Open-Drain

RESET

681Ax

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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

RQ

SQ

One Shot

Low-Voltage Detect

+

1.24V
Bandgap
Reference

GND

G680/G681

RESET

RESET

V

DD

LTH

HTH

+

+

High-Voltage Detect

Delay

Line

RQ

SQ

One Shot

Low-Voltage Detect

+

1.24V
Bandgap
Reference

GND

G680/G681

RESET

RESET

V

DD

LTH

HTH

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G680/G681

Global Mixed-mode Technology Inc.

Typical Operating Characteristics

(VCC = full range, TA = -40°C to +105°C, unless otherwise noted. Typical values are at TA = +25°C, VCC = 5V
for 463/438/400 versions, V

CC

= 3.3V for 308/293 versions, and VCC = 3V for 263 version.)

Power -Down Reset Delay

vs. Temperature

0

10

20

30

40

50

60

70

-40-20 0 20406080

Temperature(°C)

Power-Down Reset Delay(

μ

S)

VOD=10mV

V

OD=VTH-

VLTH

VOD=100mV

V

OD

=200mV

Supply Current vs.

Temperature

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

-40-200 20406080

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

-40-30-20-100 10202730405060708090

Temperature (°C)

Normalized Reset Threshold (V)

Reset Timeout Period

vs. Temperature

0

100

200

300

400

500

600

700

800

-40-30-20-100 102030405060708090

Temperature (°C)

Reset Timeout Period (ms)

VCC=5.5V

V

CC

=3V

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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

> VTH.

4

RESET

(RESET)

Reset (Output): Push-pull output. This output is asserted and latched when V

LTH

<VTH, indicating

a low voltage condition. This state remains latched until V

HTH

> VTH. The polarity of this signal

(active-high or low) is determined by the part number suffix. See ordering information.

5 VCC Power Supply (Input): Independent supply input for internal circuitry.

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 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.

Figure1. Maximum Transient Duration without

Causing a Reset Pulse vs. Reset Com­parator Overdrive

Applications Information

Negative-Going VCC 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 short­duration 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 maxi­mum 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 de­creases. 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:

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 se­lected such that they have a given total value, that is,
R1 + R2 + R3 = R

TOTAL

.

0

50

100

150

200

250

300

350

1 10 100 1000

Reset Comparator Overdrive, VTH- V

LTH

(mV)

Maximum Transient Duration (us)

G680

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G680/G681

Global Mixed-mode Technology Inc.

A value such as 1MΩ 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 3MΩ.

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 moder­ately charged. Solving for R3:

1MΩ

V

BAT (hi)

= 1.245

R3

R3 = 344kΩ

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 applica­tions limit the drain to 3.1V. Using 3.1V for the V

BAT (lo)

threshold allows calculation of the two remaining re­sistor values.

1MΩ

V

BAT (lo)

=3.1V = 1.245

R2+344k

R2 = 56kΩ

R1 = 1MΩ - R2 - R3

R 1=600kΩ

The accuracy of the resistors can be chosen based
upon the accuracy required by the system.

Figure 3. Interfacing to µPs with Bidirectional Re

set I/O

Interfacing to µPs with Bidirectional Reset Pins

Since the

RESET output on the G681L is open drain,
this device interfaces easily with µPs that have bidi­rectional reset pins, such as the Motorola 68HC11.

Connecting the µP supervisor’s

RESET output di-

rectly to the microcontroller’s (µC’s)

RESET pin with
a single pull-up resistor allows either device to assert
reset (Figure 3).

.

V

BATT

VCC

LTH

HTH

RESET
RESET

R1

R2

R3

604k
1%

56k
1%

340k
1%

G680/G681

V

BATT

VCC

LTH

HTH

RESET
RESET

R1

R2

R3

604k
1%

56k
1%

340k
1%

G680/G681

RESET
INPU T

GND

µP

V

CC

RESET

GND

G681

V

CC

V

CC

MOTOROLA

68HCXX

R

PULL-UP

RESET
INPU T

GND

µP

V

CC

RESET

GND

G681

V

CC

V

CC

MOTOROLA

68HCXX

R

PULL-UP

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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 ------ -----

θ

1

1º 5º 9º

Taping Specification

GMT Inc. d oes not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and GMT Inc. reserves the right at any time without notice to change said circuitry and specifications.

E

e

D

H

θ

1

L

C

b

A2

A1

A

e1

E

e

D

H

θ

1

L

C

b

A2

A1

A

e1

Feed Direction

SOT23-5 Package Orientation

Feed Direction

SOT23-5 Package Orientation