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PDF G680 Data sheet ( Hoja de datos )
| Número de pieza | G680 | |
| Descripción | Microprocessor Reset IC | |
| Fabricantes | Global Mixed-mode Technology | |
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Global Mixed-mode Technology Inc.
G680/G681
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
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 hystere-
sis. Voltage detection thresholds are accurate to 2%.
These circuits perform a single function: they assert a
reset signal whenever the VCC supply voltage declines
below the low-voltage threshold, keeping it asserted
for at least 140ms after VCC 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 VCC. 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.
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
HTH 1
5 Vcc
GND 2 G680/G681
LTH 3
4 RESET(RESET)
SOT23-5
() is for G680H
VCC
VCC
HTH
G680/G681
LTH RESET
(RESET)
GND
VCC
*RPULL-UP
µP
RESET
INPUT
GND
*G681 ONLY
Ver: 03 Preliminary
Jan 25 2002
TEL: 886-3-5788833
http://www.gmt.com.tw
1
1 page  
Global Mixed-mode Technology Inc.
G680/G681
Pin Description
PIN NAME
1 HTH
2 GND
3 LTH
4 RESET (RESET)
5 VCC
FUNCTION
High-Voltage Theshold (Input): Analog input to a comparator. When the level on this pin initially
rises above VTH, 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 VTH, RESET or
RESET is asserted and the condition is latched until VHTH > VTH.
Reset (Output): Push-pull output. This output is asserted and latched when VLTH <VTH, indicating
a low voltage condition. This state remains latched until VHTH > VTH. 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.
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 VTH, 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
1200
1000
800
600 G69__463/438/400
400
200 G69__308/293/263
0
1 10 100 1000
Reset Comparator Overdrive, Vth-Vcc (mV)
Figure1. Maximum Transient Duration without
Causing a Reset Pulse vs. Reset Com-
parator 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 short-
duration negative-going VLTH 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
VLTH, 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 VLTH 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 VLTH 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 VLTH pin provides
additional transient immunity.
Programming the Thresholds
The low-voltage threshold is calculated using:
R1+R2+R3
VBAT (Io) = VREF
R2+R3
The low-voltage threshold is calculated using:
VBAT (hi) = VREF
R1+R2+R3
R3
where, for both equations:
VBAT (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 = RTOTAL.
Ver: 03 Preliminary
Jan 25 2002
TEL: 886-3-5788833
http://www.gmt.com.tw
5
5 Page | ||
| Páginas | Total 7 Páginas | |
| PDF Descargar | [ Datasheet G680.PDF ] | |
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