LM2735XMFSLASHNOPB datasheet(21/58 Pages) TI1

部品番号	LM2735XMF/NOPB

部品情報	LM2735/LM2735-Q1 520kHz/1.6MHz ??Space-Efficient Boost and SEPIC DC-DC Regulator

PDF	58 Pages

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メーカー	TI1 [Texas Instruments]

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RDSON

¸¸

¨¨

NFET

COND

Isw-rms = IIND D

1 +

IIND

PIND = IIN

2 x R

IND-DCR

( )

LM2735

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SNVS485F – JUNE 2007 – REVISED APRIL 2013

Figure 30. LM2735 Switch Current

(small ripple approximation)

(28)

PCOND-NFET = IIN

2 x R

DSON x D

(29)

(30)

The value for should be equal to the resistance at the junction temperature you wish to analyze. As an example,

at 125°C and VIN = 5V, RDSON = 250 mΩ (See typical graphs for value).

Switching losses are also associated with the internal NMOS switch. They occur during the switch on and off

transition periods, where voltages and currents overlap resulting in power loss.

The simplest means to determine this loss is to empirically measuring the rise and fall times (10% to 90%) of the

switch at the switch node:

PSWR = 1/2(VOUT x IIN x FSW x TRISE)

(31)

PSWF = 1/2(VOUT x IIN x FSW x TFALL)

(32)

PSW = PSWR + PSWF

(33)

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