LTC3894
150V Low IQ Step-Down
DC/DC Controller with
100% Duty Cycle Capability
FEATURES
n Wide Operating VIN Range: 4.5V to 150V
n Wide VOUT Range: 0.8V to 60V
n 9μA IQ when Regulating 48VIN to 3.3VOUT
n 16μA IQ when Regulating 12VIN to 3.3VOUT
n Very Low Dropout Operation: 100% Duty Cycle
n Adjustable Input Overvoltage Lockout
n Programmable PGOOD Undervoltage Monitor
n RSENSE or Inductor DCR Current Sensing
n Selectable High Efficiency Burst Mode® Operation or
Pulse-Skipping Mode at Light Loads
n Programmable Fixed Frequency: 50kHz to 850kHz
n Phase-Lockable Frequency: 75kHz to 800kHz
n Internal Fixed Soft-Start and External Programmable
Soft-Start or Voltage Tracking
n Strong MOSFET Gate Driver with Selectable
Undervoltage Lockout Thresholds
n Optional External NMOS for Gate Driver Bias in High
Power Applications
APPLICATIONS
n Automotive and Industrial Power Systems
n Telecommunication Power Systems
n Distributed Power Systems
DESCRIPTION
The LTC®3894 is a high voltage step-down DC/DC switch-
ing regulator controller. It drives a P-channel power
MOSFET switch allowing 100% duty cycle operation. It
enables a low part count, simple, and robust solution for
high reliability, high voltage applications.
The LTC3894 operates over a wide input voltage range
from 4.5V to 150V and can regulate output voltages
from 0.8V to 60V. It offers excellent light load efficiency,
drawing only 9μA quiescent current while regulating the
output voltage with no load. Its peak current mode, con-
stant frequency architecture provides for good control of
switching frequency and output current limit. The switch-
ing frequency can be programmed from 50kHz to 850kHz
with an external resistor and can be synchronized to an
external clock from 75kHz to 800kHz.
The LTC3894 offers programmable output voltage soft-
start or tracking. Safety features include overvoltage,
overcurrent and overtemperature protection with a power
good output monitor with adjustable threshold.
The LTC3894 is available in a thermally enhanced 20-Pin
TSSOP package with leads removed to accommodate
high voltage creepage and clearance requirements.
All registered trademarks and trademarks are the property of their respective owners.
TYPICAL APPLICATION
High Efficiency 150V to 5V Step-Down Regulator
VIN
6V to 150V
12µF
×2
22µH 20mΩ
1nF 330µF
10µF
×2
0.47µF
3.3nF
5.76k
RUN GATE
VIN
CAP
OVLO
DRVUV/EXTG
EXTS
ITH GND FREQ
SENSE+ SENSE–
PGOOD
LTC3894
PGUV
VFB
TRACK/SS PLLIN/MODE
47pF
36.5k
0.1µF
100k
422k
80.6k
VOUT
5V, 3A
3894 TA01a
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Efficiency and Power Loss vs
Load Current
100
10k
90 Burst Mode OPERATION
80
1k
70
60
EFFICIENCY
100
50
40
10
30
POWER LOSS
20
10
0
0.0001
0.001 0.01
VIN = 12V
VIN = 24V
0.1
1
1
0.1
3
LOAD CURRENT (A)
3894 TA01b
Rev. A
1
