參數(shù)資料
型號(hào): LTC3851IMSE#TRPBF
廠商: LINEAR TECHNOLOGY CORP
元件分類: 穩(wěn)壓器
英文描述: 0.05 A SWITCHING CONTROLLER, 790 kHz SWITCHING FREQ-MAX, PDSO16
封裝: LEAD FREE, PLASTIC, MSOP-16
文件頁數(shù): 17/28頁
文件大?。?/td> 325K
代理商: LTC3851IMSE#TRPBF
LTC3851
24
3851fb
current will also help ensure that the minimum on-time
of 90ns is not violated. The minimum on-time occurs at
maximum VIN:
t
ON(MIN) =
V
OUT
V
IN(MAX) f
()
=
1.8V
22V 250kHz
()
= 327ns
The RSENSE resistor value can be calculated by connect-
ing ILIM to INTVCC and using the maximum current sense
voltage specication with some accommodation for toler-
ances. Tie ILIM to INTVCC.
R
SENSE
75mV
6A
= 0.0125Ω, so 0.01Ω is selected
Choosing 1% resistors: R1 = 25.5k and R2 = 32.4k yields
an output voltage of 1.816V.
The power dissipation on the topside MOSFET can be easily
estimated. Choosing a Fairchild FDS6982S dual MOSFET
results in: RDS(ON) = 0.035Ω/0.022Ω, CMILLER = 215pF. At
maximum input voltage with T (estimated) = 50°C:
P
MAIN =
1.8V
22V
5
()2 1+ 0.005
() 50°C25°C
()
0.035
Ω
()+ 22V
()2
5A
2
2
Ω
() 215pF
()
1
5
2.3
+
1
2.3
250kHz
()=185mW
APPLICATIONS INFORMATION
A short-circuit to ground will result in a folded back cur-
rent of:
I
SC =
29mV
0.0125
Ω
1
2
90ns 22V
()
3.3H
= 2.02A
with a typical value of RDS(ON) and δ = (0.005/°C)(25°C)
= 0.125. The resulting power dissipated in the bottom
MOSFET is:
P
SYNC =
22V
2.02A
()2 1.125
() 0.022Ω
()
= 101.0mW
which is less than under full-load conditions.
CIN is chosen for an RMS current rating of at least 3A at
temperature. COUT is chosen with an ESR of 0.02Ω for
low output ripple. The output ripple in continuous mode
will be highest at the maximum input voltage. The output
voltage ripple due to ESR is approximately:
VORIPPLE = RESR (ΔIL) = 0.02Ω (2A) = 40mVP-P
相關(guān)PDF資料
PDF描述
LTC3851IMSE#PBF 0.05 A SWITCHING CONTROLLER, 790 kHz SWITCHING FREQ-MAX, PDSO16
LTC3851IUD#TRPBF 0.05 A SWITCHING CONTROLLER, 790 kHz SWITCHING FREQ-MAX, PQCC16
LTC3851IGN#TRPBF 0.05 A SWITCHING CONTROLLER, 790 kHz SWITCHING FREQ-MAX, PDSO16
LTC3851EUD#TRPBF 0.05 A SWITCHING CONTROLLER, 790 kHz SWITCHING FREQ-MAX, PQCC16
LTC3858EUH-2#PBF DUAL SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PQCC32
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