LTM4600 LINER [Linear Technology], LTM4600 Datasheet - Page 18

• Manufacturer Part Number: LTM4600
• Description: 10A High Effi ciency DC/DC ?Module
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
LTM4600
inductor ripple current gets too high above 16V, and the
400ns minimum off-time is limited below 9V.
Equations for setting frequency:
t
~450kHz frequency or 2.22µs period is chosen for 5V to
3.3V. Frequency range is about 450kHz to 650kHz from
4.5V to 7V input.
18
OFF
I
frequency = (I
duty cycle is (V
t = t
switching period; t = 1/frequency
t
t
ON
ON
ON
must be greater than 400ns, or t – t
= V
= DC • t
= 0.66 • 2.22µs ≅ 1.46ns
ON
IN
+ t
– 0.7V/110k; for 5V input, I
OFF
ON
, t
OUT
/[2.4V • 10pF]) • DC; DC = duty cycle,
ON
U
/V
= on-time, t
IN
12V TO 5V AT 8A WITH f
)
5V TO 3.3V AT 8A WITH f
U
RUN/SOFT-START
RUN/SOFT-START
C3
10µF
25V
C3
10µF
25V
9V TO 16V
4.5V TO 7V
C1
10µF
25V
OFF
C1
10µF
25V
W
= off-time of the
ADJ
ON
ADJ
ON
= 15k
= 30.1k
EXTV
FCB
RUN/SS
COMP
EXTV
FCB
RUN/SS
COMP
= 39µA
> 400ns.
CC
CC
SGND
SGND
U
V
V
IN
LTM4600EV
IN
LTM4600EV
5V to 3.3V at 8A
12V to 5V at 8A
PGND
PGND
f
f
ADJ
ADJ
PGOOD
PGOOD
V
V
V
V
OSET
SV
30.1k
OSET
SV
C1, C3: TDK C3216X5R1E106MT
C2: TAIYO YUDEN, JMK316BJ226ML
C4: SANYO POS CAP, 6TPE330MIL
C1, C3: TDK C3216X5R1E106MT
C2: TAIYO YUDEN, JMK316BJ226ML
C4: SANYO POS CAP, 6TPE330MIL
4600 F19
4600 F18
15k
OUT
OUT
R1
R1
IN
IN
t
band.
Using the frequency = (I
I
calculated from 5V input was 39µA, so a resistor from f
to ground = (0.7V/30.1k) = 23µA. 39µA – 23µA = 16µA,
sets the adequate I
for the higher duty cycle conversion of 5V to 3.3V. Input
voltage range is limited to 4.5V to 7V. Higher input voltages
can be used without the 30.1k on f
current gets too high above 7V, and the 400ns minimum
off-time is limited below 4.5V.
ON
ON
t
OFF
= (450kHz • 2.4V • 10pF) • (1/0.66) ≅ 16µA. I
OPEN DRAIN
and t
OPEN DRAIN
= 2µs – 1.32ns ≅ 760ns
C5
100pF
OFF
C5
100pF
are above the minimums with adquate guard
5V AT 8A
3.3V AT 8A
R2
22.1k
1%
R2
13.7k
1%
ON
C2
22µF
C2
22µF
EFFICIENCY = 93%
EFFICIENCY = 93%
current for proper frequency range
ON
+
+
/[2.4V • 10pF]) • DC, solve for
C4
330µF
6.3V
C4
330µF
6.3V
ADJ
. The inductor ripple
ON
current
4600fa
ADJ