Final Electrical Specifications
LT3433
High Voltage
Step-Up/Step-Down
DC/DC Converter
September 2003
FEATURES
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DESCRIPTION
The LT
®
3433 is a 200kHz fixed-frequency current mode
switching regulator that provides both step-up and step-
down regulation using a single inductor. The IC operates
over a 4V to 60V input voltage range making it suitable for
use in various wide input voltage range applications such
as automotive electronics that must withstand both load
dump and cold crank conditions.
Internal control circuitry monitors system conditions and
converts from single switch buck operation to dual switch
bridged operation when required, seamlessly changing
between step-down and step-up voltage conversion.
Optional Burst Mode
®
operation reduces no-load quies-
cent current to 100µA and maintains high efficiencies with
light loads.
Current limit foldback and frequency foldback help pre-
vent inductor current runaway during start-up. Program-
mable soft-start helps prevent output overshoot at start-up.
The LT3433 is available in a 16-lead thermally enhanced
TSSOP package.
Automatic Step-Up and Step-Down Conversion
Uses a Single Inductor
Wide 4V to 60V Input Voltage Range
V
OUT
from 3.3V to 20V
Dual Internal 500mA Switches
100µA No-Load Quiescent Current
Low Current Shutdown
±1%
Output Voltage Accuracy
200kHz Operating Frequency
Boosted Supply Pin to Saturate High Side Switch
Frequency Foldback Protection
Current Limit Foldback Protection
Current Limit Unaffected by Duty Cycle
16-lead Thermally Enhanced TSSOP Package
APPLICATIO S
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12V Automotive Systems
Wall Adapter Powered Systems
Battery Power Voltage Buffering
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
L1
100µH
CoEv DU1352-101M
4V to 60V to 5V DC/DC Converter
with Burst Mode Operation
B160A
V
OUT
5V
4V
≤
V
IN
≤
8.5V: 125mA
8.5V
≤
V
IN
≤
60V: 350mA
Maximum Output
Current vs V
IN
500
V
OUT
= 5V
MAXIMUM OUTPUT CURRENT (mA)
BUCK
400
1N4148
V
BST
V
IN
4V TO 60V
0.1µF
SW_H
V
IN
1nF100pF
68k
V
FB
100k
0.5%
305k
0.5%
SGND
0.01µF
SS
BURST_EN
V
C
PWRGND
V
OUT
LT3433
SW_L
B120A
47µF
+
2.2µF
300
EFFICIENCY (%)
1N4148
V
BIAS
0.1µF
SHDN
200
BRIDGED
100
0
0
10
20
3433 TA01
30
V
IN
(V)
40
50
60
3433 TA01c
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
U
U
U
Efficiency
90
80
V
IN
= 13.8V
70
60
50
40
30
20
0.1
V
IN
= 4V
10
100
1
OUTPUT CURRENT (mA)
1000
3433 TA01b
3433ia
1
LINER [ LINEAR TECHNOLOGY ]
