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参数资料
| 型号： | G691L308T22 |
| 厂商： | Global Mixed-mode Technology Inc. |
| 元件分类： | 复位半导体 |
| 英文描述： | Microprocessor Reset IC |
| 中文描述： | 微处理器复位IC |
| 文件页数： | 11/12页 |
| 文件大小： | 219K |
| 代理商： | G691L308T22 |
Ver: 1.3
Oct 31, 2002
TEL: 886-3-5788833
http://www.gmt.com.tw
8
G690/G691
Global Mixed-mode Technology Inc.
Pin Description
PIN
NAME
FUNCTION
1
GND
Ground
(G691L/G690L)
RESET
Output remains low while VCC is below the reset threshold, and for at least 140ms after
VCC rises above the reset threshold.
2
RESET
(G690H)
RESET Output remains high while VCC is below the reset threshold, and for at least 140ms after
VCC rises above the reset threshold.
3
VCC
Supply Voltage (+5V, +3.3V, +3.0V)
Detailed Description
A microprocessor’s (P’s) reset input starts the P in a
known state. The G691L/G690L/G690H 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, keeping it asserted for at
least 140ms after VCC has risen above the reset
threshold. The G691L uses an open-drain output, and
the G690L/G690H have a push-pull output stage.
Connect a pull-up resistor on the G691L’s RESET out-
put to any supply between 0 and 5.5V.
Figure 1. Maximum Transient Duration Without
Causing a Reset Pulse vs. Reset Com-
parator Overdrive
Figure2. RESET Valid to VCC = Ground Circuit
Applications Information
Negative-Going VCC Transients
In addition to issuing a reset to the P during
power-up, power-down, and brownout conditions, the
G691L/G690H/G690L are relatively immune to short-
duration negative-going VCC transients (glitches).
Figure 1 shows typical transient duration vs. reset
comparator overdrive, for which the G691L/G690H/
G690L do not generate a reset pulse. The graph was
generated using a negative-going pulse applied to VCC,
starting 0.5V 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 VCC 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, for the G69_ _463 and G69_ _438,
a VCC 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 VCC pin provides additional transient
immunity.
Ensuring a Valid Reset Output Down to VCC = 0
When VCC falls below 1V, the G690 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 P and other circuitry is inoperative with VCC
below 1V. However, in applications where RESET
must 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; 100k
is large enough not to load
RESET and small enough to pull RESET to ground.
A 100k
pull-up resistor to VCC is also recommended
for the G691L if RESET is required to remain valid
for VCC < 1V.
V
CC
RESET
GND
G690
R1
100k
V
CC
RESET
GND
G690
R1
100k
0
100
200
300
400
500
600
1
10
100
1000
Reset Comparator Overdrive, VTH- VCC (mV)
M
ax
im
um
T
rans
ient
D
u
ra
tion(
u
s)
G69_ _ 308/293/263
G69_ _ 463/438/400
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| G691L308T23 | 制造商:GMT 制造商全称:Global Mixed-mode Technology Inc 功能描述:Microprocessor Reset IC |
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