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參數(shù)資料
| 型號： | L4938E |
| 廠商： | 意法半導(dǎo)體 |
| 英文描述： | ADVANCED VOLTAGE REGULATOR |
| 中文描述： | 高級穩(wěn)壓器 |
| 文件頁數(shù)： | 6/12頁 |
| 文件大?。?/td> | 101K |
| 代理商： | L4938E |
Connectinga resistordivider R
1E
, R
2E
to the ADJ,
OUT2 pin the output voltage 2 can be pro-
grammed to the value of
V
OUT2
=
V
OUT1
1
+
R
1E
(
R
2E
+
R
ADJ
)
R
2E
R
ADJ
with R
ADJ
= 60K to 150K and V
OUT1
= 4.95 to
5.05V.
For an exact calculation the temperature coeffi-
cient (Tc -2000pprm) of the internal resistor
(R
ADJ
) must be taken into account.Pin ADJ in this
mode should not have a capacitive burden be-
cause this would reduce the phase margin of the
regulatorloop.
Reset circuit
The reset circuit supervises the standby output
voltage. The reset output (RES) is defined from
V
OUT
≥
1V.
Even if V
S
is lacking, the reset generator is sup-
plied by the output voltageV
OUT1
.
The reset thresholdof 4.7V is defined with the in-
ternal reference voltage (note 9) and standby out-
put divider, when pin PR is left open. The reset
threshold voltage can be programmed in the
range from 3.8V to 4.7V by connecting an exter-
nal resistorfrom pin PR to GND.
The value of the programming resistor R
PR
can
be calculatedwith:
R
PR
=
22K
4.7K
V
RT
1
92.9K,
3.8V
≤
V
RT
≤
4.7V
The reset pulse delay time t
RD
, is defined with the
charge time of an externalcapacitor C
T
:
t
RDmin
=
C
T
0.6V
1
μ
A
(note5)
t
RDnom
=
C
T
1.4V
1
μ
A
(note 6)
The reaction time of the reset circuit originates
from the noise immunity. 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 approximately50
μ
s.
The minimum rset time is generated if reset con-
dition only occures for a short time triggering a re-
set pulse but not completely discharging C
T
. The
reset can be related to output2 on request. If
higher charge currents for the reset capacitor are
required a resistors from Pin C
T
to OUT1, may be
used to increase the current. We recommended
the use of 10K
to 5V as an outputpull up.
Sense Comparator
The sense comparator compares an input signal
with an internalvoltage reference of typical 1.23V.
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 be-
fore or after the protection diode and to giveaddi-
tional information to the microprocessor like low
voltage warnings. We recommended the use of
10K
to 5V as an output pull up.
Note 9:
The referenceis alternativelysuppliedfrom V
S
orV
OUT1
. Ifonesupply
is present, the reference is operating.
ThermalProtection
Both outputs are provided with an overtempera-
ture shut down regulation power dissipation down
to uncritical values.
Output 2 will shut down approximately 10K before
output 1.
Under normal conditions shut down of output 2
will allow the chip to cool down again. Thus out-
put 1 will be unaffected.
The thermal shut down reduces the output volt-
ages until power dissipation and the flow of ther-
mal energy out of the chip balance.
TransientSensitivity
In proper operation(V
OUT
> 4.5V) the reference is
supplied by V
OUT1
thus reducing sensitivity to in-
put transients.
Precise Data will be issued as soon as samples
are available.
L4938E - L4938ED - L4938EPD
6/12
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| L4938ED | ADVANCED VOLTAGE REGULATOR |
| L4938EPD | ADVANCED VOLTAGE REGULATOR |
| L4938NPD | DUAL MULTIFUNCTION VOLTAGE REGULATOR |
| L4938N | DUAL MULTIFUNCTION VOLTAGE REGULATOR |
| L4938ND | DUAL MULTIFUNCTION VOLTAGE REGULATOR |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| L4938ED | 功能描述:低壓差穩(wěn)壓器 - LDO Dual 5V Very LDO RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| L4938ED013TR | 功能描述:低壓差穩(wěn)壓器 - LDO Dual 5V Very LDO RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| L4938EDTR-E | 制造商:STMicroelectronics 功能描述:PTS SMARTPOWER - Tape and Reel 制造商:STMicroelectronics 功能描述:Advanced Voltage Reg 3.8V to 4.7V 65uA |
| L4938EPD | 功能描述:低壓差穩(wěn)壓器 - LDO Dual 5V Very LDO RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| L4938EPD13TR | 功能描述:低壓差穩(wěn)壓器 - LDO Dual 5V Very LDO RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
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