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參數(shù)資料
| 型號(hào)： | LT1108-12 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | Micropower DC/DC Converter Adjustable and Fixed 5V, 12V |
| 中文描述： | 微功率DC / DC轉(zhuǎn)換可調(diào)和固定5V，12V的 |
| 文件頁(yè)數(shù)： | 11/12頁(yè) |
| 文件大小： | 266K |
| 代理商： | LT1108-12 |
11
LT1108
U
S
A
Figure 8 details current limit circuitry. Sense transistor Q1,
whose base and emitter are paralleled with power switch
Q2, is ratioed such that approximately 0.5% of Q2’s
collector current flows in Q1’s collector. This current
passed through internal 80
resistor R1 and out through
the I
LIM
pin. The value of the external resistor connected
between I
LIM
and V
IN
sets the current limit. When sufficient
switch current flows to develop a V
BE
across R1 + R
LIM
, Q3
turns on and injects current into the oscillator, turning off
the switch. Delay through this circuitry is approximately
2
μ
s. The current trip point becomes less accurate for
switch-ON times less than 5
μ
s. Resistor values program-
ming switch-ON time for 2
μ
s or less will cause spurious
response in the switch circuitry although the device will
still maintain output regulation.
O
PPLICATI
U
U
Figure 9. Setting Low Battery Detector Trip Point
LT1108 F09
R1
R2
1.245V
REF
SET
GND
IN
V
LT1108
47k
5V
TO
PROCESSOR
R1 = V
LB
– 1.25V
35.1
μ
A
V
= BATTERY TRIP POINT
R2 = 33k
R3 = 1.6M
+
–
AO
R3
V
BAT
Table 1. Inductor Manufacturers
MANUFACTURER
Coiltronics International
984 S.W. 13th Court
Pompano Beach, FL 33069
305-781-8900
Sumida Electric Co. USA
708-956-0666
PART NUMBERS
OCTA-PAC
TM
Series
CD54
CDR74
CDR105
Table 2. Capacitor Manufacturers
MANUFACTURER
Sanyo Video Components
1201 Sanyo Avenue
San Diego, CA 92073
619-661-6322
Nichicon America Corporation
927 East State Parkway
Schaumberg, IL 60173
708-843-7500
AVX Corporation
Myrtle Beach, SC
803-946-0690
PART NUMBERS
OS-CON Series
PL Series
TPS Series
Table 3. Transistor Manufacturers
MANUFACTURER
Zetex Inc.
87 Modular Avenue
Commack, NY 11725
516-543-7100
PART NUMBERS
ZTX 749 (NPN)
ZTX 849 (NPN)
ZTX 949 (PNP)
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
USING THE GAIN BLOCK
The gain block (GB) on the LT1108 can be used as an error
amplifier, low battery detector or linear post regulator. The
gain block itself is a very simple PNP input op amp with an
open collector NPN output. The negative input of the gain
block is tied internally to the 1.245V reference. The positive
input comes out on the SET pin.
Arrangement of the gain block as a low battery detector
is straightforward. Figure 9 shows hookup. R1 and R2
need only be low enough in value so that the bias current
of the SET input does not cause large errors. 33k for R2
is adequate. R3 can be added to introduce a small amount
of hysteresis. This will cause the gain block to “snap”
when the trip point is reached. Values in the 1M to 10M
range are optimal. The addition however, of R3 will
change the trip point.
Figure 8. LT1108 Current Limit Circuitry
LT1108 F08
SW2
SW1
DRIVER
OSCILLATOR
V
IN
I
LIM
R1
80
(INTERNAL)
R
(EXTERNAL)
Q1
Q2
Q3
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相關(guān)代理商/技術(shù)參數(shù) |
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|---|---|
| LT1108-5 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Micropower DC/DC Converter Adjustable and Fixed 5V, 12V |
| LT1108CN8 | 功能描述:IC REG BUCK BST INV ADJ .4A 8DIP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(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 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 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 |
| LT1108CN8#PBF | 功能描述:IC REG BUCK BST INV ADJ .4A 8DIP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(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 |
| LT1108CN8-12 | 功能描述:IC REG BUCK BST INV 12V .4A 8DIP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(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 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 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 |
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