1
LTC1624
FEATURES
DESCRIPTIO
N
U
■
N-Channel MOSFET Drive
■
Implements Boost, Step-Down, SEPIC
and Inverting Regulators
■
Wide V
IN
Range: 3.5V to 36V Operation
■
Wide V
OUT
Range: 1.19V to 30V in Step-Down
Configuration
■
±
1% 1.19V Reference
■
Low Dropout Operation: 95% Duty Cycle
■
200kHz Fixed Frequency
■
Low Standby Current
■
Very High Efficiency
■
Remote Output Voltage Sense
■
Logic-Controlled Micropower Shutdown
■
Internal Diode for Bootstrapped Gate Drive
■
Current Mode Operation for Excellent Line and
Load Transient Response
■
Available in an 8-Lead SO Package
■
Notebook and Palmtop Computers, PDAs
■
Cellular Telephones and Wireless Modems
■
Battery-Operated Digital Devices
■
DC Power Distribution Systems
■
Battery Chargers
TYPICAL APPLICATIO
N
U
The LTC
®
1624 is a current mode switching regulator
controller that drives an external N-channel power MOSFET
using a fixed frequency architecture. It can be operated in
all standard switching configurations including boost,
step-down, inverting and SEPIC. Burst Mode
TM
operation
provides high efficiency at low load currents. A maximum
high duty cycle limit of 95% provides low dropout operation
which extends operating time in battery-operated systems.
The operating frequency is internally set to 200kHz, allowing
small inductor values and minimizing PC board space. The
operating current level is user-programmable via an external
current sense resistor. Wide input supply range allows
operation from 3.5V to 36V (absolute maximum).
A multifunction pin (I
TH
/ RUN) allows external
compensation for optimum load step response plus
shutdown. Soft start can also be implemented with the
I
TH
/RUN pin to properly sequence supplies.
Figure 1. High Efficiency Step-Down Converter
+
+
SENSE
–
I
TH
/RUN
V
FB
GND
V
IN
BOOST
TG
SW
LTC1624
1000pF
100pF
C
C
470pF
R
C
6.8k
D1
MBRS340T3
C
B
0.1
µ
F
R2
35.7k
R1
20k
C
OUT
100
µ
F
10V
×
2
M1
Si4412DY
L1
10
µ
H
R
SENSE
0.05
Ω
C
IN
22
µ
F
35V
×
2
V
OUT
3.3V
2A
V
IN
4.8V TO 28V
1624 F01
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
High Efficiency SO-8
N-Channel Switching
Regulator Controller
APPLICATIO
N
S
U
