LTM4600HVMPV View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTM4600HVMPV' PDF : 24 Pages View PDF
LTM4600HV
applications information
tON = 0.41 • 1µs @ 410ns
tOFF = 1µs – 410ns @ 590ns
tON and tOFF are above the minimums with adequate guard
band.
Using the frequency = (ION/[2.4V • 10pF]) • DC, solve for
ION = (1MHz • 2.4V • 10pF) • (1/0.41) @ 58µA. ION current
calculated from 12V input was 103µA, so a resistor from
fADJ to ground = (0.7V/15k) = 46µA. 103µA – 46µA =
57µA, sets the adequate ION current for proper frequency
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 fADJ. The
inductor ripple current gets too high above 16V, and the
400ns minimum off-time is limited below 9V.
Equations for setting frequency for 5V to 3.3V:
ION = (VIN – 0.7V)/110k; ION = 39µA
frequency = (ION/[2.4V • 10pF]) • DC = 1.07MHz;
DC = duty cycle, duty cycle is (VOUT/VIN)
tS = tON + tOFF, tON = on-time, tOFF = off-time of the
switching period; tS = 1/frequency
tOFF must be greater than 400ns, or tS – tON > 400ns.
tON = DC • tS
~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.
tON = 0.66 • 2.22µs @ 1.46µs
tOFF = 2.22µs – 1.46µs @ 760ns
tON and tOFF are above the minimums with adequate guard
band.
Using the frequency = (ION/[2.4V • 10pF]) • DC, solve for
ION = (450kHz • 2.4V • 10pF) • (1/0.66) @ 16µA. ION current
calculated from 5V input was 39µA, so a resistor from fADJ
to ground = (0.7V/30.1k) = 23µA. 39µA – 23µA = 16µA,
sets the adequate ION current for proper frequency range
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 fADJ. The inductor ripple
current gets too high above 7V, and the 400ns minimum
off-time is limited below 4.5V.
5V to 3.3V at 8A
4.5V TO 7V
C3
10μF
25V
C1
10μF
25V
RUN/SOFT-START
R1
30.1k
VIN
EXTVCC
fADJ
VOUT
FCB
LTM4600HV
RUN/SS
VOSET
SVIN
COMP
SGND
PGOOD
PGND
4600 F22
C5
100pF
3.3V AT 8A
R2
22.1k
1%
EFFICIENCY = 94%
C2 +
22μF
C4
330μF
6.3V
OPEN DRAIN
5V TO 3.3V AT 8A WITH fADJ = 30.1k
LTM4600HV MINIMUM ON-TIME = 100ns
LTM4600HV MINIMUM OFF-TIME = 400ns
C1, C3: TDK C3216X5R1E106MT
C2: TAIYO YUDEN, JMK316BJ226ML
C4: SANYO POSCAP, 6TPE330MIL
For more information www.linear.com/LTM4600HV
4600hvfe
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