ltm4601ahv Linear Technology Corporation, ltm4601ahv Datasheet - Page 10

• Manufacturer Part Number: ltm4601ahv
• Description: 12a, 28vin Dc/dc ?module With Pll, Output Tracking And Margining
• Manufacturer: Linear Technology Corporation

LTM4601AHV
APPLICATIONS INFORMATION
The typical LTM4601AHV application circuits are shown in
Figures 19 and 20. External component selection is primar-
ily determined by the maximum load current and output
voltage. Refer to Table 2 for specifi c external capacitor
requirements for a particular application.
V
There are restrictions in the maximum V
down ratio that can be achieved for a given input voltage.
These constraints are shown in the Typical Performance
Characteristics curves labeled “V
Ratio”. Note that additional thermal derating may apply. See
the Thermal Considerations and Output Current Derating
section of this data sheet.
Output Voltage Programming and Margining
The PWM controller has an internal 0.6V reference voltage.
As shown in the Block Diagram, a 1M and a 60.4k 0.5%
internal feedback resistor connects V
together. The V
and the 60.4k resistor. The 1M resistor is used to protect
against an output overvoltage condition if the V
pin is not connected to the output, or if the remote sense
amplifi er output is not connected to V
voltage will default to 0.6V. Adding a resistor R
V
Table 1. Standard 1% Resistor Values
10
R
(kΩ)
V
IN
FB
(V)
OUT
SET
V
to V
pin to SGND pin programs the output voltage:
OUT
Open
OUT
0.6
=
0 6
.
Step-Down Ratios
V
60.4
1.2
OUT_LCL
60 4
.
R
40.2
k R
1.5
SET
+
pin is connected between the 1M
SET
30.1
1.8
25.5
IN
2
to V
OUT_LCL
OUT
19.1
2.5
IN
OUT
and V
and V
. The output
SET
Step-Down
13.3
3.3
OUT
from the
OUT_LCL
FB
8.25
step
pins
5
The MPGM pin programs a current that when multiplied
by an internal 10k resistor sets up the 0.6V reference ±
offset for margining. A 1.18V reference divided by the
RPGM resistor on the MPGM pin programs the current.
Calculate V
where %V
and V
where R
pin to ground.
The output margining will be ± margining of the value.
This is controlled by the MARG0 and MARG1 pins. See
the truth table below:
Input Capacitors
LTM4601AHV module should be connected to a low AC
impedance DC source. Input capacitors are required to
be placed adjacent to the module. In Figure 18, the 10μF
ceramic input capacitors are selected for their ability to
handle the large RMS current into the converter. An input
bulk capacitor of 100μF is optional. This 100μF capacitor is
only needed if the input source impedance is compromised
by long inductive leads or traces.
R
V
OUT MARGIN
PGM
OUT(MARGIN)
MARG1
HIGH
HIGH
LOW
LOW
(
PGM
=
OUT
OUT(MARGIN)
V
0 6
OUT
.
is the resistor value to place on the MPGM
is the percentage of V
V
)
=
•
is the margin quantity in volts:
V
%
OUT MARGIN
100
V
1 18
OUT
:
.
(
MARG0
HIGH
HIGH
LOW
LOW
V
•
V
OUT
)
•
OUT
10
k
you want to margin,
MARGIN DOWN
NO MARGIN
MARGIN UP
NO MARGIN
MODE
4601ahvf