LTM4603IV-1#PBF Linear Technology, LTM4603IV-1#PBF Datasheet - Page 19

• Manufacturer Part Number: LTM4603IV-1#PBF
• Description: IC DC/DC UMODULE 6A 118-LGA
• Manufacturer: Linear Technology
• Series: µModuler
• Type: Point of Load (POL) Non-Isolatedr

Specifications of LTM4603IV-1#PBF

• Design Resources: LTM4603-1 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: 118-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: 93%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• 3rd Output: -
• 2nd Output: -

Example for 5V Output
Equations for setting frequency:
I
= ((4.8 • 10pF)/I
is 33.2k. Frequency = (V
~ 1MHz. The inductor ripple current begins to get high at
the higher input voltages due to a larger voltage across the
inductor. This is noted in the “Inductor Ripple Current vs
Duty Cycle” graph at ~5A at 25% duty cycle. The inductor
ripple current can be lowered at the higher input voltages by
adding an external resistor from f
the switching frequency. A 3A ripple current is chosen, and
the total peak current is equal to 1/2 of the 3A ripple current
plus the output current. The 5V output current is limited
to 5A, so total peak current is less than 6.5A. This is below
the 7A peak specifi ed value. A 150k resistor is placed from
f
33.2k equates to 27.2k. The I
and 20V input voltage equals 245μA. This equates to a t
of 196ns. This will increase the switching frequency from
1MHz to ~1.28MHz for the 20V to 5V conversion. The
minimum on time is above 100ns at 20V input. Since
the switching frequency is approximately constant over
input and output conditions, then the lower input voltage
range is limited to 10V for the 1.28MHz operation due to
the 400ns minimum off time. Equation: t
• (1/Frequency) equates to a 382ns on time, and a 400ns
off time. The “V
an operating range of 10V to 20V for 1.28MHz operation
with a 150k resistor to ground, and an 8V to 16V operation
for f
wider input voltage ranges for the 5V output designs while
limiting the inductor ripple current, and maintaining the
400ns minimum off time.
APPLICATIONS INFORMATION
fSET
SET
LTM4603 minimum on-time = 100ns;
t
LTM4603 minimum off-time = 400ns; t
where t = 1/Frequency
Duty Cycle = t
ON
SET
to ground, and the parallel combination of 150k and
= (V
= ((4.8 • 10pf)/I
fl oating. These modifi cations are made to provide
IN
/(3 • R
IN
fSET
fSET
ON
to V
), t
/t or V
)), for 20V operation, I
OUT
ON
fSET
OUT
= 239ns, where the internal R
Step-Down Ratio” curve refl ects
OUT
)
/(V
/V
IN
fSET
IN
• t
SET
ON
calculation with 27.2k
to ground to increase
)) = (5V/(20 • 239ns))
fSET
ON
OFF
= (V
= 201μA, t
= t – t
OUT
ON
/V
fSET
,
IN
ON
ON
)
Example for 3.3V Output
Equations for setting frequency:
I
t
R
• 164ns)) ~ 1MHz. The minimum on-time and minimum-
off time are within specifi cation at 164ns and 836ns. The
4.5V minimum input for converting 3.3V output will not
meet the minimum off-time specifi cation of 400ns. t
733ns, Frequency = 1MHz, t
Solution
Lower the switching frequency at lower input voltages to
allow for higher duty cycles, and meet the 400ns mini-
mum off-time at 4.5V input voltage. The off-time should
be about 500ns with 100ns guard band. The duty cycle
for (3.3V/4.5) = ~73%. Frequency = (1 – DC)/t
(1 – 0.73)/500ns = 540kHz. The switching frequency needs
to be lowered to 540kHz at 4.5V input. t
or 1.35μs. The f
and the I
33.2k. The I
operation. A resistor can be placed from V
lower the effective I
The f
82.5k will source 21μA into the f
I
and the 4.5V to 20V input operation for down converting
to 3.3V output. The frequency will scale from 540kHz to
1.2MHz over this input range. This provides for an effective
output current of 5A over the input range.
fSET
ON
fSET
fSET
LTM4603 minimum on-time = 100ns;
t
LTM4603 minimum off-time = 400ns;
t
Duty Cycle (DC) = t
ON
OFF
= ((3.3 • 10pf)/I
= (V
current to 24μA. This enables the 540kHz operation
SET
is 33.2k. Frequency = (V
= ((3.3 • 10pF)/I
= t – t
IN
pin is 4.5V/3 =1.5V and V
fSET
/(3 • R
fSET
ON
current equates to 45μA with the internal
LTM4603/LTM4603-1
, where t = 1/Frequency
SET
fSET
current needs to be 24μA for 540kHz
fSET
fSET
pin voltage compliance is 1/3 of V
)), for 20V operation, I
ON
fSET
), t
current out of the f
/t or V
ON
)
OFF
= 164ns, where the internal
OUT
OUT
= 267ns.
SET
/(V
/V
OUT
IN
IN
node and lower the
ON
• t
= 3.3V, therefore
ON
= DC/frequency,
SET
)) = (3.3V/(20
OUT
fSET
pin to 24μA.
to f
= 201μA,
19
OFF
SET
ON
4603fa
, or
IN
to
=
,