LT3844 데이터 시트보기 (PDF) - Linear Technology
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LT3844 Datasheet PDF : 24 Pages
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LT3844
PI FU CTIO S
BOOST (Pin 16): The BOOST pin is the supply for the
bootstrapped gate drive and is externally connected to a
low ESR ceramic boost capacitor referenced to SW pin.
The recommended value of the BOOST capacitor,CBOOST,
is 50 times greater than the total input capacitance of the
topside MOSFET. In most applications 0.1μF is adequate.
W
FU CTIO AL DIAGRA
The maximum voltage that this pin sees is VIN + VCC,
ground referred.
Exposed Pad (SGND) (Pin 17): The exposed leadframe is
internally connected to the SGND pin. Solder the exposed
pad to the PCB ground for electrical contact and optimal
thermal performance.
VIN
VIN
1
CIN
RA
SHDN
2
RB
BURST_EN
4
VFB
5
R1 R2
CC2
RC
CC1
VC
6
3
CSS
VIN
UVLO
(<4V)
8V
REGULATOR
3.8V
REGULATOR
VCC
UVLO
(<6V)
INTERNAL
SUPPLY RAIL
VREF
–+
FEEDBACK
REFERENCE
1.231V
BST
UVLO
BOOSTED SWITCH
DRIVER
BOOST
16
CBOOST
DRIVE
CONTROL
NOL
SWITCH
LOGIC
DRIVE
CONTROL
DRIVER
TG
15
SW
14
VCC
13
D2
CVCC
PGND
12
– gm +
ERROR
AMP
0.5V
100mV
CSS CLAMPED TO
VFB + VBE
~1V SOFT-START
BURST DISABLE
VREF + 200mV
2μA
50μA
FAULT CONDITION:
VIN UVLO
VCC UVLO
VSHDN UVLO
QS
R
CURRENT
SENSE
COMPARATOR
OSCILLATOR
SLOPE COMP
GENERATOR
SYNC
7
fSET
8
RSET
BURST MODE
OPERATION
–+
SGND
9
SENSE+
11
SENSE–
10
M1
L1 RSENSE
D1
VOUT
COUT
D3
(OPTIONAL)
3844 FD
3844fa
7
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