LTM4600HVMPV#PBF Linear Technology, LTM4600HVMPV#PBF Datasheet - Page 17

• Manufacturer Part Number: LTM4600HVMPV#PBF
• Description: IC DC/DC UMODULE 10A 104-LGA
• Manufacturer: Linear Technology
• Series: µModuler
• Type: Point of Load (POL) Non-Isolatedr

Specifications of LTM4600HVMPV#PBF

• Output: 0.6 ~ 5 V
• Number Of Outputs: 1
• Power (watts): 50W
• Mounting Type: Surface Mount
• Voltage - Input: 4.5 ~ 28 V
• Package / Case: 104-LGA
• 1st Output: 0.6 ~ 5 VDC @ 10A
• Size / Dimension: 0.59" L x 0.59" W x 0.11" H (15mm x 15mm x 2.8mm)
• Power (watts) - Rated: 50W
• Operating Temperature: -55°C ~ 125°C
• Efficiency: 92%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• 3rd Output: -
• 2nd Output: -

APPLICATIO S I FOR ATIO
LTM4600HV Frequency Adjustment
The LTM4600HV is designed to typically operate at 850kHz
across most input and output conditions. The control ar-
chitecture is constant on time valley mode current control.
The f
optional 1000pF capacitor. The switching frequency has
been optimized to maintain constant output ripple over the
operating conditions. The equations for setting the operat-
ing frequency are set around a programmable constant on
time. This on time is developed by a programmable current
into an on board 10pF capacitor that establishes a ramp
that is compared to a voltage threshold equal to the output
voltage up to a 2.4V clamp. This I
I
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 the following waveform. The on time is
equal to t
frequency is equal to: Frequency = DC/t
ON
= (V
ADJ
ON
IN
IN
. The I
C
to f
pin is typically left open or decoupled with an
ON
IN
IN
– 0.7V)/110k, with the 110k onboard resistor
OFF
Figure 20. Recommended PCB Layout
V
PGND
ADJ
. The on time is proportional to V
= (V
IN
= t
ON
LOAD
. The on time is equal to t
OUT
s
current is proportional to V
U
– t
/I
ON
ON
V
OUT
. The frequency is equal to: Freq.
) • 10pF and t
U
TOP LAYER
ON
W
current is equal to:
OFF
ON
ON
).
= t
4600hv F20
= (V
s
OUT
IN
– t
U
, and the
IN
OUT
ON
, there-
up to a
. The
/I
ON
)
The LTM4600HV has a minimum (t
nanoseconds and a minimum (t
nanoseconds. The 2.4V clamp on the ramp threshold as
a function of V
increase by the ratio of V
This is due to the fact the on time will not increase as V
increases past 2.4V. Therefore, if the nominal switch-
ing frequency is 850kHz, then the switching frequency
will increase to ~1.2MHz for 3.3V, and ~1.7MHz for 5V
outputs due to Frequency = (DC/t
frequency increases to 1.2MHz, then the time period t
reduced 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.
OFF
OFF
I
frequency = (I
DC = duty cycle, duty cycle is (V
t
switching period; t
t
ON
S
ON
will be below the 400ns minimum off time. A resistor
must be greater than 400ns, or t
= t
= (V
= DC • t
ON
ADJ
IN
+ t
– 0.7V)/110k; I
pin to ground can shunt current away from
S
(DC) DUTY CYCLE =
OFF
OUT
t
OFF
, t
ON
PERIOD t
will cause the switching frequency to
ON
/[2.4V • 10pF]) • DC = 1.79MHz;
S
= 1/frequency
= on-time, t
OUT
s
t
ON
/2.4V for 3.3V and 5V outputs.
t
ON
ON
t
s
= 103μA
LTM4600HV
ON
4602 F25
DC =
FREQ =
OFF
OUT
) When the switching
OFF
ON
S
) off time of 400
t
ON
t
/V
– t
s
) on time of 100
= off-time of the
t
DC
ON
=
IN
ON
V
V
)
OUT
IN
S
> 400ns.
= t
ON
17
+ t
4600hvfc
OUT
OFF
S
is
,