LT3800 Datasheet, PDF (1/24 Pages) Linear Technology – High-Voltage Synchronous Current Mode Step-Down Controller

FEATURES
■ _{Wide 4V to 60V Input Voltage Range}
■ _{Output Voltages up to 36V}
■ _{Adaptive Nonoverlap Circuitry Prevents Switch}
Shoot-Through
■ _{Reverse Inductor Current Inhibit for Discontinuous}
Operation Improves Efficiency with Light Loads
■ _{Output Slew Rate Controlled Soft-Start with}
Auto-Reset
■ _{100µA No Load Quiescent Current}
■ _{Low 10µA Current Shutdown}
■ _{1% Regulation Accuracy}
■ _{200kHz Operating Frequency}
■ _{Standard Gate N-Channel Power MOSFETs}
■ _{Current Limit Unaffected by Duty Cycle}
■ _{Reverse Overcurrent Protection}
■ _{16-Lead Thermally Enhanced TSSOP Package}
U
APPLICATIO S
■ _{12V and 42V Automotive and Heavy Equipment}
■ _{48V Telecom Power Supplies}
■ _{Avionics and Industrial Control Systems}
■ _{Distributed Power Converters}
LT3800
High-Voltage Synchronous
Current Mode Step-Down
DESCRIPTIO
Controller
The LT^®3800 is a 200kHz fixed frequency high voltage
synchronous current mode step-down switching regula-
tor 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.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark 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 APPLICATIO
12V 75W DC/DC Converter with Reverse Current Inhibit and Input UVLO
V_IN
20V TO 55V ₊
56µF
×2
V_IN
BOOST
1M
82.5k
TG
LT3800
SHDN
SW
1.5nF _200k
C_SS
20k
1%
174k
1%
BURST_EN V_CC
V_FB
BG
100pF 82.5k
680pF
V_C
PGND
SENSE^– SENSE⁺
SGND
1µF
×3
1µF
Si7850DP
BAS19
1N4148
1µF
Si7370DP
Efficiency and Power Loss
15µH
100
6
V_IN = 24V
95
V_IN = 36V
5
V_IN = 60V
90
4
V_IN = 48V
85
3
B160
80
2
LOSS (48V)
75
1
0.015Ω
+
10µF
V_OUT
12V AT 75W
270µF
3800 TA01a
70
0.1
1
I_LOAD (A)
0
10
3800 TA01b
3800fb
1