Datasheet

LT3740
15
3740fc
APPLICATIONS INFORMATION
Which is adequately lower than the 35mV reverse current
comparator threshold.
C
IN
is chosen for an RMS current rating of about 5A at
85°C. The output capacitors are chosen for a low ESR
of 0.005Ω to minimize output voltage changes due to
inductor ripple current and load steps. The ripple voltage
will be only:
ΔV
OUT(RIPPLE)
= ΔI
L
• (ESR) = (3.47A)(0.005) = 17mV
However, a 0A to 10A load step will cause an output
change of up to:
ΔV
OUT(STEP)
= ΔI
LOAD
• (ESR) = (10A)(0.005Ω)= 50mV
An optional 100µF ceramic output capacitor is included to
minimize the effect of ESL in the output ripple.
For the step-up converter, at V
IN
= 7V, step-up inductor
current is about 27mA. Choose a 22µH inductor and a
1µF output capacitor.
The complete circuit is shown in Figure 4.
Figure 4. Design Example: 2.5V/10A Output
SWB
V
IN
SHDN
100k
100k
1
µF
XREF
RANGE
PGOOD
V
C
BGDP
BIAS
TGATE
SW
PGND
BGATE
GND
LT3740
SN
+
SN
–
FB
3740 F04
L1
2.0µH
C
B
1µF
V
OUT
2.5V
10A
V
IN
7V to 20V
M1
Si4840
M2
Si4840
R
S
12mΩ
100µF
6.3V
680µF
4V
s 2
C
IN
100µF
35V
L2
22µH
100k
100pF
18pF
10k
21k
D1
6CWQ03FN