Datasheet > LTC1174-5

LTC1174-5

更新时间： 2022-11-27 02:16:08

品牌	Logo	应用领域
凌特 - Linear		转换器
页数	文件大小	规格书
16页	354K
描述
High Efficiency Step-Down and Inverting DC/DC Converter

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LTC1174-5 数据手册

LTC1174

LTC1174-3.3/LTC1174-5

FU CTIO AL DIAGRA

(Pin 1 connection shown for LTC1174-3.3 and LTC1174-5, changes create LTC1174)

LIM2

LIM1

PGM

SENSE

SLEEP

0.1Ω

TH2

–

RESET

SET

(V )

OUT FB

TH1

R1*

OUT

–

31.5k

SHUTDOWN

1.25V

REFERENCE

GND

1174 BD

* R1 = 51k FOR LTC1174-3.3

R1 = 93.5k FOR LTC1174-5

(Refer to Functional Diagram)

OPERATIO

The LTC1174 uses a constant off-time architecture to

switch its internal P-channel power MOSFET. The off-time

is set by an internal timing capacitor and the operating

frequency is a function of V_IN.

The timing capacitor, C_T, begins to discharge until its

voltage goes below V_TH1. Comparator A4 will then trip,

which resets the flip-flop and causes the switch to turn on

again. Also, the timing capacitor is recharged. The inductor

current will again ramp up until the current comparator A2

trips. The cycle then repeats.

The output voltage is set by an internal resistive divider

(LTC1174-3.3 and LTC1174-5) or an external divider re-

turned to V_FBpin 1 (LTC1174). A voltage comparator A1

compares the divided output voltage to a reference voltage

of 1.25V.

When the load is relatively light, the LTC1174 automatically

goes into Burst Mode operation. The current mode loop is

interrupted when the output voltage reaches the desired

regulated value. The hysteretic voltage comparator A1 trips

when V_OUTis above the desired output voltage, shutting off

the switch and causing the timing capacitor to discharge.

This capacitor discharges past V_TH1until its voltage drops

below V_TH2. Comparator A5 then trips and a sleep signal is

generated.

Tooptimizeefficiency, theLTC1174automaticallyswitches

between continuous and Burst Mode^TMoperation. The volt-

age comparator is the primary control element when the

device is in Burst Mode operation, while the current com-

parator controls the output voltage in continuous mode.

During the switch“ON” time, switch current flows through

the 0.1Ω sense resistor. When this current reaches the

thresholdofthecurrentcomparatorA2,itsoutputsignalwill

change state, setting the flip-flop and turning the switch off.

In sleep mode, the LTC1174 is in standby and the load

current is supplied by the output capacitor. All unused

Burst Mode^TMis a trademark of Linear Technology Corporation.

1...3 4 567 8 9...16

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