LT3430IFE Linear Technology, LT3430IFE Datasheet - Page 23

• Manufacturer Part Number: LT3430IFE
• Description: IC REG SW STDN 3A 200KHZ 16TSSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LT3430IFE

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.2 ~ 54 V
• Current - Output: 3A
• Frequency - Switching: 200kHz
• Voltage - Input: 5.5 ~ 60 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-TSSOP Exposed Pad, 16-eTSSOP, 16-HTSSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

APPLICATIONS INFORMATION
LT3430/LT3430-1 will consume their quiescent operating
current of 1.5mA. The V
any other components connected to the input line. If this
load is greater than 10mA or the input could be shorted to
ground, a series Schottky diode must be added, as shown
in Figure 12. With these safeguards, the output can be held
at voltages up to the V
BUCK CONVERTER WITH ADJUSTABLE SOFT-START
Large capacitive loads or high input voltages can cause
high input currents at start-up. Figure 13 shows a circuit
that limits the dv/dt of the output at start-up, controlling
the capacitor charge rate. The buck converter is a typical
confi guration with the addition of R3, R4, C
the output starts to rise, Q1 turns on, regulating switch
current via the V
C
pin to maintain a constant dv/dt at the
REMOVABLE
IN
INPUT
IN
absolute maximum rating.
pin will also source current to
INPUT
40V
54k
25k
30BQ060
Figure 12. Dual Source Supply with 25µA Reverse Leakage
D3
Figure 13. Buck Converter with Adjustable Soft-Start
C3
4.7µF
50V
CER
C3
4.7µF
V
SHDN
SS
SYNC
IN
0.022µF
BOOST
and Q1. As
LT3430
C
3.3k
V
SHDN
SYNC
GND
GND
C
0.022µF
R
IN
C
BIAS
LT3430
BOOST
3.3k
C
R
C
V
SW
C
FB
C
C
220pF
BIAS
F
0.68µF
V
SW
FB
C
C2
C
220pF
F
D1
30BQ060
OR B250A
Q1
output. Output rise time is controlled by the current through
C
regulation, Q1 turns off and the circuit operates normally.
R3 is transient protection for the base of Q1.
Using the values shown in Figure 10,
The ramp is linear and rise times in the order of 100ms are
possible. Since the circuit is voltage controlled, the ramp
rate is unaffected by load characteristics and maximum
output current is unchanged. Variants of this circuit can
be used for sequencing multiple regulator outputs.
SS
MMSD914TI
Rise Time
Rise Time
defi ned by R4 and Q1’s V
33µH
D1
30BQ060
D2
R4
47k
L1
100µF
C2
0.68µF
R3
2k
33µH
10V
L1: CDRH104R-220M
C1
15nF
C
+
SS
MMSD914TI
=
=
R1
15.4k
R2
4.99k
D2
( )(
(
R1
15.4k
R2
4.99k
R
47 10
3430 F13
4
+
•
C
5V, 2A
C1
100µF
10V
V
LT3430/LT3430-1
SS
3
BE
OUTPUT
5V
2A
)(
)(
0 7
15 10
V
.
OUT
ALTERNATE
•
SUPPLY
BE
. Once the output is in
)
3430 F12
–
9
)
( )
5
=
5
ms
23
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