參數(shù)資料
型號(hào): L4949N
廠商: MOTOROLA INC
元件分類: 基準(zhǔn)電壓源/電流源
英文描述: MULTIFUNCTION VERY LOW DROPOUT VOLTAGE REGULATOR
中文描述: 5 V FIXED POSITIVE LDO REGULATOR, 0.5 V DROPOUT, PDIP8
封裝: PLASTIC, DIP-8
文件頁數(shù): 7/8頁
文件大?。?/td> 191K
代理商: L4949N
L4949
7
MOTOROLA ANALOG IC DEVICE DATA
Reset Circuit
The block circuit diagram of the reset circuit is shown in
Figure 15.
The reset circuit supervises the output voltage. The reset
thereshold of 4.5 V is defined with the internal reference
voltage and standby output drivider.
The reset pulse delay time tRD, is defined with the charge
time of an external capacitor CT:
tRD
CTx 2.0 V
2.0
A
The reaction time of the reset circuit originates from the
discharge time limitation of the reset capacitor CT and is
proportional to the value of CT. The reaction time of the reset
circuit increases the noise immunity.
1.23 V Vref
22 k
Out
Reg
2.0
μ
A
CT
2.0 V
+
Reset
Figure 15. Reset Circuit
Standby output voltage drops below the reset threshold
only a bit longer than the reaction time results in a shorter
reset delay time.
The nominal reset delay time will be generated for standby
output voltage drops longer than approximately 50
μ
s. The
typical reset output waveforms are shown in Figure 16.
VRT + 0.1 V
5.0 V
UKT
Vout
3.0 V
Reset
Vout1
Vin
40 V
t
tR
tRD
tRD
tRR
Switch On
Input Drop
Dump
Output
Overload
Switch Off
Figure 16. Typical Reset Output Waveforms
Sense Comparator
The sense comparator compares an input signal with an
internal voltage reference of typical 1.23 V. The use of an
external voltage divider makes this comparator very flexible
in the application.
It can be used to supervise the input voltage either before
or after the protection diode and to give additional information
to the microprocessor like low voltage warnings.
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