LTM4602IV#PBF Linear Technology, LTM4602IV#PBF Datasheet - Page 17

• Manufacturer Part Number: LTM4602IV#PBF
• Description: IC DC/DC UMODULE 6A 104-LGA
• Manufacturer: Linear Technology
• Series: µModuler
• Type: Point of Load (POL) Non-Isolatedr

Specifications of LTM4602IV#PBF

• Design Resources: LTM4602 Spice Model
• Output: 0.6 ~ 5 V
• Number Of Outputs: 1
• Power (watts): 30W
• Mounting Type: Surface Mount
• Voltage - Input: 4.5 ~ 20V
• Package / Case: 104-LGA
• 1st Output: 0.6 ~ 5 VDC @ 6A
• Size / Dimension: 0.59" L x 0.59" W x 0.11" H (15mm x 15mm x 2.8mm)
• Power (watts) - Rated: 30W
• Operating Temperature: -40°C ~ 85°C
• Efficiency: 92%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• 3rd Output: -
• 2nd Output: -

APPLICATIONS INFORMATION
from V
• 10pF and t
= DC/t
regulator duty cycle is inversely proportional to V
fore the step-down regulator will remain relatively constant
frequency as the duty cycle adjustment takes place with
lowering V
2.4V clamp. This will hold frequency relatively constant
with different output voltages up to 2.4V. The regulator
switching period is comprised of the on time and off time
as depicted in Figure 19.
The LTM4602 has a minimum (t
onds and a minimum (t
The 2.4V clamp on the ramp threshold as a function of
V
ratio of V
the fact the on time will not increase as V
past 2.4V. Therefore, if the nominal switching frequency
is 850kHz, then the switching frequency will increase
OUT
will cause the switching frequency to increase by the
ON
IN
C
IN
. The I
OUT
to f
IN
V
PGND
OFF
IN
Figure 18. Recommended PCB Layout
Figure 19. LTM4602 Switching Period
. The on time is proportional to V
ADJ
/2.4V for 3.3V and 5V outputs. This is due to
LOAD
ON
= t
(DC) DUTY CYCLE =
. The on time is equal to t
t
OFF
s
current is proportional to V
– t
PERIOD t
ON
V
OUT
OFF
. The frequency is equal to: Freq.
s
) off time of 400 nanoseconds.
t
TOP LAYER
ON
t
ON
t
s
ON
) on time of 100 nanosec-
4602 F19
DC =
FREQ =
t
ON
t
s
t
DC
ON
ON
=
V
OUT
4600 F16
V
OUT
IN
= (V
OUT
IN
increases
, and the
IN
OUT
, there-
up to a
/I
ON
)
to ~1.2MHz for 3.3V, and ~1.7MHz for 5V outputs due
to Frequency = (DC/t
increases to 1.2MHz, then the time period t
to ~833 nanoseconds and at 1.7MHz the switching period
reduces to ~588 nanoseconds. When higher duty cycle
conversions like 5V to 3.3V and 12V to 5V need to be
accommodated, then the switching frequency can be
lowered to alleviate the violation of the 400ns minimum
off time. Since the total switching period is t
t
from the f
the on time generator, thus allowing for a longer on time
and a lower switching frequency. 12V to 5V and 5V to
3.3V derivations are explained in the data sheet to lower
switching frequency and accommodate these step-down
conversions.
Equations for setting frequency for 12V to 5V:
t
1MHz frequency or 1μs period is chosen for 12V to 5V.
t
band.
Using the frequency = (I
I
calculated from 12V input was 103μA, so a resistor from
f
57μA, sets the adequate I
range for the higher duty cycle conversion of 12V to
5V. Input voltage range is limited to 9V to 16V. Higher
input voltages can be used without the 15k on f
inductor ripple current gets too high above 16V, and the
400ns minimum off-time is limited below 9V.
OFF
OFF
ON
ON
ADJ
I
frequency = (I
DC = duty cycle, duty cycle is (V
t
switching period; t
t
t
t
ON
S
ON
ON
OFF
and t
= (1MHz • 2.4V • 10pF) • (1/0.41) ≅ 58μA. I
will be below the 400ns minimum off time. A resistor
must be greater than 400ns, or t
to ground = (0.7V/15k) = 46μA. 103μA – 46μA =
= t
= (V
= DC • t
= 0.41 • 1μs ≅ 410ns
= 1μs – 410ns ≅ 590ns
ON
OFF
ADJ
IN
+ t
are above the minimums with adequate guard
– 0.7V)/110k; I
pin to ground can shunt current away from
S
OFF
, t
ON
ON
/[2.4V • 10pF]) • DC = 1.79MHz;
ON
S
= on-time, t
= 1/frequency
) When the switching frequency
ON
ON
/[2.4V • 10pF]) • DC, solve for
ON
current for proper frequency
= 103μA
OUT
OFF
S
/V
– t
LTM4602
= off-time of the
IN
ON
)
S
S
> 400ns.
= t
is reduced
ON
ON
ADJ
17
current
+ t
. The
4602fa
OFF
,