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參數(shù)資料
| 型號： | L4954 |
| 廠商： | 意法半導(dǎo)體 |
| 英文描述： | Quad Multifunction Voltage Regulator for Car Radio(用于汽車收音機的多功能四電壓穩(wěn)壓器) |
| 中文描述： | 四多功能電壓調(diào)節(jié)汽車收音機（用于汽車收音機的多功能四電壓穩(wěn)壓器） |
| 文件頁數(shù)： | 5/7頁 |
| 文件大小： | 74K |
| 代理商： | L4954 |
FUNCTIONAL DESCRIPTION
The L4954 includes a monitoring circuit to warn
the microprocessor if a low voltage or no voltage
condition is occurring.
When the voltage on the STCAP pin drops below
7.5V (typ), the LVW output will go low. This tells
the microprocessor to stop executing code and
save vitalinformation. The reset outputwill go low
when REG4 (5V-STBY) drops below (V
REG4
-
250mV) or 4.75V is minimum value. The RESET
output doesn’t go above 0.4V until REG4 has
gone back above 4.75V (min).
Any spike will tell the microprocessor to start op-
erating. Once the STCAP line passes 7.5V (typ),
the LVWarn output will also return to high state.
The STCAP pin acts like a delay circuit. Due to
the large capacitor (470
μ
F), the STCAP pin al-
lows the batteryvoltage to decayslowly giving the
microprocessortime to store data.
Also, during short low voltage or negativevoltage
conditions, the STCAP pin protects the 5V STBY
output from dropping below the RESET and LVW
trip points. The four outputs are expected to fol-
low the battery voltage down
9V for REG2, 6V forREG3 and REG4.
The L4954 has a STBY mode to keep the micro-
processor and memories alive during an ignition
off conditions. The EN1 input pin is controlled by
the microprocessor. A high on the EN1input turns
on REG1, REG2, REG3, and HSD1. A Low on
EN1 places the part in stand-by mode with REG4
on. The High side driver outputs HSD2 and HSD3
are controlled by EN2 and EN3 respectively: a
Low on the control input turns the corresponding
high side driver off.
to 11V for REG1,
ELECTRICALCHARACTERISTICS
(Continued)
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
LVWARN OUTPUT
TH
LVW
V
LVW
LVW Threshold onSTCAP
LVW Output Voltage
7.5
V
V
V
STCAP <7.5V; V
IL
= ”0”
STCAP >7.5V V
IH
= ”1”
C
LVW
= 0.1
μ
F
C
LVW
= 0.1
μ
F
0
0.4
5
2.75
t
rise
t
fall
LVW Output Rise Time
LVW Output Fall Time
3.9
12.6
ms
μ
s
RESET OUTPUT
TH
RES
V
RES
Reset Threshold on Reg 4
Reset Output Voltage
4.5
V
V
Set V
S
sothat V
OUT5STBY
<4.5V;
V
IL
= ”0”
Set V
S
so that V
OUT5STBY
is not
less than normal REG4 output
voltage; V
IH
= ”1”
C
RESET
= 0.1
μ
F
C
RESET
= 0.1
μ
F
0
0.4
2.75
5
V
t
rise
t
fall
Reset Output Rise Time
Reset Output Fall Time
4.5
37
ms
μ
s
STCAP
(V)
0
7.5
7.5
TIME
4.75
4.75
REG4
(V)
5
0
5
0.4
5
LVWarn
(V)
RESET
(V)
TIME
TIME
TIME
D95AU349A
TIMING DIAGRAM
L4954
5/7
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