LT3800_15 Datasheet, PDF (1/24 Pages) Linear Technology – High-Voltage Synchronous Current Mode Step-Down Controller

FEATURES
n _{Wide 4V to 60V Input Voltage Range}
n _{Output Voltages up to 36V}
n _{Adaptive Nonoverlap Circuitry Prevents Switch}
Shoot-Through
n _{Reverse Inductor Current Inhibit for Discontinuous}
Operation Improves Efficiency with Light Loads
n _{Output Slew Rate Controlled Soft-Start with}
Auto-Reset
n _{100μA No Load Quiescent Current}
n _{Low 10μA Current Shutdown}
n _{1% Regulation Accuracy}
n _{200kHz Operating Frequency}
n _{Standard Gate N-Channel Power MOSFETs}
n _{Current Limit Unaffected by Duty Cycle}
n _{Reverse Overcurrent Protection}
n _{16-Lead Thermally Enhanced TSSOP Package}
APPLICATIONS
n _{12V and 42V Automotive and Heavy Equipment}
n _{48V Telecom Power Supplies}
n _{Avionics and Industrial Control Systems}
n _{Distributed Power Converters}
LT3800
High-Voltage Synchronous
Current Mode Step-Down
Controller
DESCRIPTION
The LT^®3800 is a 200kHz fixed frequency high voltage
synchronous current mode step-down switching regulator
controller. The IC drives standard gate N-channel power
MOSFETs and can operate with input voltages from 4V to
60V. An onboard regulator provides IC power directly from
V_IN and provides for output-derived power to minimize
V_IN quiescent current. MOSFET drivers employ an internal
dynamic bootstrap feature, maximizing gate-source “ON”
voltages during normal operation for improved operating
efficiencies. The LT3800 incorporates Burst Mode^® opera-
tion, which reduces no load quiescent current to under
100μA. Light load efficiencies are also improved through
a reverse inductor current inhibit, allowing the controller
to support discontinuous operation. Both Burst Mode
operation and the reverse-current inhibit features can be
disabled if desired. The LT3800 incorporates a program-
mable soft-start that directly controls the voltage slew rate
of the converter output for reduced startup surge currents
and overshoot errors. The LT3800 is available in a 16-lead
thermally enhanced TSSOP package.
L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
and No R_SENSE and ThinSOT are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents including
5481178, 6611131, 6304066, 6498466, 6580258.
TYPICAL APPLICATION
12V 75W DC/DC Converter with Reverse Current Inhibit and Input UVLO
V_IN
20V TO 55V
+ _56μF
×2
V_IN
BOOST
1M
TG
82.5k
LT3800
SHDN
SW
1.5nF _200k
C_SS
20k
1%
174k
1%
BURST_EN V_CC
V_FB
BG
1μF
×3
1μF
Si7850DP
BAS19
1N4148
1μF
Si7370DP
15μH
B160
100pF 82.5k
680pF
V_C
PGND
SENSE^– SENSE⁺
SGND
0.015Ω
+
10μF
V_OUT
12V AT 75W
270μF
3800 TA01a
Efficiency and Power Loss
100
6
V_IN = 24V
95
V_IN = 36V
5
V_IN = 60V
90
4
V_IN = 48V
85
3
80
2
LOSS (48V)
75
1
70
0.1
1
I_LOAD (A)
0
10
3800 TA01b
3800fc
1