參數(shù)資料
型號(hào)： LT1931ES5
文件頁(yè)數(shù)： 7/12頁(yè)
文件大小： 210K
代理商： LT1931ES5
7
LT1931/LT1931A
START-UP/SOFT-START
For most LT1931/LT1931A applications, the start-up in-
rush current can be high. This is an inherent feature of
switching regulators in general since the feedback loop is
saturated due to V
OUT
being far from its final value. The
APPLICATIOU
W
U
U
regulator tries to charge up the output capacitor as quickly
as possible, which results in a large inrush current. Fig-
ure6 shows a typical oscillograph of the start-up wave-
form for the application of Figure 1 starting into a load of
33
. The lower waveform shows SHDN being pulsed
from 0V to 5V. The middle waveform shows the input
current, which reaches as high as 0.8A. The total time
required for the output to reach its final value is approxi-
mately 500
μ
s. For some applications, this initial inrush
current may not be acceptable. If a longer start-up time is
acceptable, a soft-start circuit consisting of R
SS
and C
SS
,
as shown in Figure 7, can be used to limit inrush current
to a lower value. Figure 8 shows the relevant waveforms
with R
SS
= 15k and C
SS
= 33nF. Input current, measured
at V
IN
, is limited to a peak value of 0.5A as the time required
to reach final value increases to 1ms. In Figure 9, C
SS
is
V
20mV/DIV
AC COUPLED
I
L1A
+ I
0.5A/DIV
AC COUPLED
200mA
100mA
LOAD
CURRENT
100
μ
s/DIV
1931 F04
Figure 4. Transient Response of Inverting Converter
with 220pF Phase Lead Capacitor
V
0.1V/DIV
AC COUPLED
I
L1A
+ I
0.5A/DIV
AC COUPLED
200mA
100mA
LOAD
CURRENT
50
μ
s/DIV
1931 F05
Figure 5. Transient Response of Inverting Converter with 22
μ
F
Tantalum Output Capacitor and No Phase Lead Capacitor
V
IN
V
IN
5V
V
SS
V
OUT
V
–5V
1931 F07
SW
L1A
10
μ
H
CURRENT
PROBE
L1B
10
μ
H
D1
GND
LT1931
C1
4.7
μ
F
R
SS
15k
D2
1N4148
C
SS
33nF/68nF
C3
22
μ
F
C2
1
μ
F
R2
10k
R1
29.4k
C4
220pF
NFB
SHDN
+
C1: TAIYO YUDEN X5R JMK212BJ475MG
C2: TAIYO YUDEN X5R LMK212BJ105MG
C3: TAIYO YUDEN XR5 JMK325BJ226MM
D1: ON SEMICONDUCTOR MBR0520
L1: SUMIDA CLS62-100
Figure 7. R
SS
and C
SS
at SHDN Pin Provide Soft-Start to LT1931 Inverting Converter
V
2V/DIV
I
IN
0.5A/DIV
AC COUPLED
5V
0V
V
SHDN
500
μ
s/DIV
1931 F06
Figure 6. Start-Up Waveforms for 5V to –5V Application
(Figure 1). No Soft-Start Circuit. V
OUT
Reaches –5V in
500
μ
s; Input Current Peaks at 800mA
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LT1931ES5#PBF 制造商:Linear Technology 功能描述:Conv DC-DC Single Inv 2.45V to 16V 5-Pin TSOT-23 制造商:Linear Technology 功能描述:IC SEMICONDUCTOR ((NS)) 制造商:Linear Technology 功能描述:IC, DC/DC CONVERTER, 5-TSOT-23; Primary Input Voltage:16V; No. of Outputs:1; Output Voltage:-12V; Output Current:350mA; No. of Pins:5; Operating Temperature Min:-40C; Operating Temperature Max:85C; MSL:MSL 1 - Unlimited ;RoHS Compliant: Yes
LT1931ES5#PBF 制造商:Linear Technology 功能描述:IC
LT1931ES5#TR 功能描述:IC REG INV 1A TSOT23-5 RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開(kāi)關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開(kāi)關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無(wú) 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC
LT1931ES5#TRM 功能描述:IC REG INV 1A TSOT23-5 RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開(kāi)關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開(kāi)關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無(wú) 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC
LT1931ES5#TRMPBF 功能描述:IC REG INV 1A TSOT23-5 RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開(kāi)關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:250 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V 輸入電壓:2.05 V ~ 6 V PWM 型:電壓模式 頻率 - 開(kāi)關(guān):2MHz 電流 - 輸出:500mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:6-UFDFN 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:6-SON（1.45x1） 產(chǎn)品目錄頁(yè)面:1032 (CN2011-ZH PDF) 其它名稱:296-25628-2
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