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PDF G685 Data sheet ( Hoja de datos )
| Número de pieza | G685 | |
| Descripción | (G684 / G685) Microprocessor Reset IC | |
| Fabricantes | GMT | |
| Logotipo |  |
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Global Mixed-mode Technology Inc.
G684/G685
Microprocessor Reset IC
Features
Precision Monitoring of +3V, +3.3V, and +5V
Power-Supply Voltages
Fully Specified Over Temperature
Available in Three Output Configurations
Push-Pull RESET Output (G684L)
Push-Pull RESET Output (G684H)
Open-Drain RESET Output (G685L)
14µA Supply Current
Guaranteed Reset Valid to VCC = 0.8V
Power Supply Transient Immunity
5 pin SOT23-5 Packages
2% Threshold Accuracy
Applications
Computers
Controllers
Intelligent Instruments
Critical µP and µC Power Monitoring
Portable / Battery-Powered Equipment
Automotive
Pin Configuration
General Description
The G684/G685 are microprocessor (µP) supervisory
circuits used to monitor the power supplies in µP and
digital systems. They provide excellent circuit reliability
and low cost and adjustments when used with +5V,
+3.3V, +3.0V- powered circuits.
These circuits perform a single function: they assert a
reset signal whenever the VCC supply voltage declines
below a preset threshold, with hysteresis after VCC has
risen above the reset threshold. Reset thresholds
suitable for operation with a variety of supply voltages
are available.
The G685 has an open-drain output stage, while the
G684 have push-pull outputs. The G685L’s open-drain
RESET output requires a pull-up resistor that can be
connected to a voltage higher than VCC. The G684L
have an active-low RESET output, while the G684H
has an active-high RESET output. The reset com-
parator is designed to ignore fast transients on VCC,
and the outputs are guaranteed to be in the correct
logic state for VCC down to 0.8V.
Low supply current makes the G684/G685 ideal for
use in portable equipment. The G684/G685 are avail-
able in 5-pin SOT23-5 packages.
Ordering Information
ORDER NUMBER TEMP. RANGE PACKAGE
G684H(L)xxxT1U -40°C ~ +105°C
SOT23-5
G685LxxxT1U
-40°C ~ +105°C
SOT23-5
Note: T1 : SOT23-5
U : Tape & Reel
* xxx specifies the threshold voltage.
e.g. 263 denotes the 2.63V threshold voltage.
Typical Application Circuit
N.C. 1
5 VCC
GND 2 G684/G685
GND 3
SOT23-5
()is for G684H
4 RESET
(RESET)
VCC
VCC
G684/G685
RESET
(RESET)
GND
Rpull-up*
VCC
µP
RESET
INPUT
GND
*G685 ONLY
Ver: 1.2
Jun 03, 2004
TEL: 886-3-5788833
http://www.gmt.com.tw
1
1 page  
Global Mixed-mode Technology Inc.
G684/G685
Pin Description
PIN NAME
1
N.C.
No Connection.
2,3
GND
Ground
FUNCTION
4
RESET
(G684L/G685L)
RESET Output remains low while
rises above the reset threshold.
VCC
is
below
the
reset
threshold,
and
for
2ms
typical
after
VCC
RESET (G684H)
RESET Output remains high while VCC is below the reset threshold, and for 2ms typical after VCC
rises above the reset threshold.
5 VCC Supply Voltage (+5V, +3.3V, +3.0V)
Detailed Description
A microprocessor’s (µP’s) reset input starts the µP in a
known state. The G685L/G684L/G684H assert reset to
prevent code-execution errors during power-up,
power-down, or brownout conditions. They assert a
reset signal whenever the VCC supply voltage declines
below a preset threshold (VTH-), VCC has risen above
the high reset threshold VTH+ (VTH-+VHYS). The G685L
uses an open-drain output, and the G684L/G684H
have a push-pull output stage. Connect a pull-up resistor
on the G685L’s RESET output to any supply between 0
and 5.5V.
Ensuring a Valid Reset Output Down to VCC = 0
When VCC falls below 0.8V, the G684 RESET output
no longer sinks current—it becomes an open circuit.
Therefore, high-impedance CMOS logic inputs con-
nected to RESET can drift to undetermined voltages.
This presents no problem in most applications since
most µP and other circuitry is inoperative with VCC be-
low 0.8V. However, in applications where RESET ust
be valid down to 0V, adding a pull-down resistor to
RESET causes any stray leakage currents to flow to
ground, holding RESET low (Figure 2). R1’s value is
not critical; 100kΩ is large enough not to load RESET
and small enough to pull RESET to ground.
A 100kΩ pull-up resistor to VCC is also recommended
for the G685L if RESET is required to remain valid for
VCC < 0.8V.
VCC
G684
RESET
GND
R1
100k
Figure2. RESET Valid to VCC = Ground Circuit
Ver: 1.2
Jun 03, 2004
TEL: 886-3-5788833
http://www.gmt.com.tw
5
5 Page | ||
| Páginas | Total 7 Páginas | |
| PDF Descargar | [ Datasheet G685.PDF ] | |
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