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參數(shù)資料
| 型號(hào)： | L4903 |
| 廠商： | 意法半導(dǎo)體 |
| 英文描述： | DUAL 5V REGULATOR WITH RESET AND DISABLE FUNCTIONS |
| 中文描述： | 5V的雙帶復(fù)位和禁用功能調(diào)節(jié) |
| 文件頁(yè)數(shù)： | 4/8頁(yè) |
| 文件大?。?/td> | 140K |
| 代理商： | L4903 |
TEST CIRCUIT
Figure 1 :
P.C.Board and ComponentsLayout of the Test Circuit
APPLICATION INFORMATION
In powersupplies for
μ
P systems it is necessary to
provide power continuously to avoid loss of infor-
mation inmemories and in time of day clocks,or to
savedatawhentheprimarysupplyisremoved.The
L4903 makes it very easy to supply such equip-
ments; itprovidestwo voltageregulators(both 5V
high precision) with separate inputs plus a reset
outputforthedatasave functionandReg.2disable
input.
CIRCUIT OPERATION
(see Figure 2)
After switch on Reg. 1 saturatesuntil V
01
rises to
the nominal value.
When the input 2 reaches V
IT
and the output 1 is
higherthan V
RT
theoutput2(V
02
andV
R
) switches
on and the reset output (V
R
) goes low after a
programmabletime T
RD
(timing capacitor).
V
02
is switched at low level and V
R
at high level
when one of the followingconditions occurs ;
- a high level (> V
DT
) is applied on pin 5 ;
- an input overvoltage;
- an overloadon the output 1 (V
01
< V
RT
) ;
- a switch off (V
IN
< V
IT
- V
ITH
) ;
and they start again as before when the condition
is removed.
An overload on output 2 does not switch Reg. 2,
and does not influenceReg. 1.
The V
01
output features:
- 5 V internal reference without voltage divider
between the output and the error comparator
- very low drop series regulator element utilizing
current mirrors
permit high output impedance and then very low
leakage current even in power conditions.
Thisoutputmaythereforebeusedtosupplycircuits
continuously, such as volatile RAMs, allowing the
use of a back-upbattery.
The V
02
cansupply other nonessential5 V circuits
which may be powereddown when the system is
inactive, or thatmust bepowered down to prevent
uncorrect operationfor supply voltages below the
minimumvalue.
Theresetoutputcanbeusedasa”P(pán)OWERDOWN
INTERRUPT”, permitting RAM access only in cor-
rectpowerconditions,orasa ”BACK-UPENABLE”
to transfer data into in a NV SHADOW MEMORY
when the supplyis interrupted.
The disablefunctioncan beused for remote on/off
controlof circuits connectedto the V
02
output.
L4903
4/8
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