Datasheet

LTM4612
11
4612fb
applicaTions inForMaTion
Output Voltage Programming and Margining
The PWM controller has an internal 0.6V reference voltage.
As shown in the Block Diagram, a 100k internal feedback
resistor connects the V
OUT
and V
FB
pins together. Adding a
resistor, R
FB
, from the V
FB
pin to the SGND pin programs
the output voltage.
V
OUT
= 0.6V •
100k
+
R
FB
R
FB
or equivalently,
R
FB
=
100k
V
OUT
0.6V
− 1
Table 1. R
FB
Standard 1% Resistor Values vs V
OUT
V
OUT
(V) 3.3 5 6 8 10 12 14 15
R
FB
(kW) 22.1 13.7 11 8.06 6.34 5.23 4.42 4.12
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
Table 2. Output Voltage Response vs Component Matrix (Refer to Figure 20)
TYPICAL MEASURED VALUES
VENDORS PART NUMBER VENDORS PART NUMBER
Murata GRM32ER61C476KEI5L (47µF, 16V) Murata GRM32ER71H106K (10µF, 50V)
Murata GRM32ER61C226KE20L (22µF, 16V) TDK C3225X5RIC226M (22µF, 16V)
V
OUT
(V)
C
IN
(CERAMIC)
C
IN
(BULK)
C
OUT1
(CERAMIC)
C
OUT2
(BULK)
V
IN
(V)
DROOP
(mV)
PEAK-TO-
PEAK (mV)
RECOVERY
TIME (µs)
LOAD STEP
(A/µs)
R
FB
(kΩ)
5 2 × 10µF 50V 100µF 50V 2 × 22µF 16V 150µF 25V 12 86 156 26 3 13.7
5 2 × 10µF 50V 100µF 50V 4 × 47µF 16V None 12 86 178 14.8 3 13.7
5 2 × 10µF 50V 100µF 50V 2 × 22µF 16V 150µF 25V 24 83 166 27 3 13.7
5 2 × 10µF 50V 100µF 50V 4 × 47µF 16V None 24 86 169 14.8 3 13.7
5 2 × 10µF 50V 100µF 50V 2 × 22µF 16V 150µF 25V 36 86 178 25 3 13.7
5 2 × 10µF 50V 100µF 50V 4 × 47µF 16V None 36 86 172 15.2 3 13.7
10 2 × 10µF 50V 100µF 50V 2 × 22µF 16V 150µF 25V 24 111 209 30 3 6.34
10 2 × 10µF 50V 100µF 50V 4 × 47µF 16V None 24 171 325 35 3 6.34
10 2 × 10µF 50V 100µF 50V 2 × 22µF 16V 150µF 25V 36 108 197 35 3 6.34
10 2 × 10µF 50V 100µF 50V 4 × 47µF 16V None 36 153 288 39 3 6.34
12 2 × 10µF 50V 100µF 50V 2 × 22µF 16V 150µF 25V 24 153 281 37 3 5.23
12 2 × 10µF 50V 100µF 50V 4 × 47µF 16V None 36 184 375 34.4 3 5.23
15 2 × 10µF 50V 100µF 50V 2 × 22µF 16V 150µF 25V 28 178 338 70 3 4.12
15 2 × 10µF 50V 100µF 50V 4 × 47µF 16V None 36 134 250 70 3 4.12
R
PGM
resistor on the MPGM pin programs the current.
Calculate V
OUT(MARGIN)
:
V
OUT(MARGIN)
=
%V
OUT
100
• V
OUT
Where %V
OUT
is the percentage of V
OUT
to be margined,
and V
OUT(MARGIN)
is the margin quantity in volts:
R
PGM
=
V
OUT
0.6V
•
1.18V
V
OUT(MARGIN)
• 10k
Where R
PGM
is the resistor value to place on the MPGM
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:
MARG1 MARG0 MODE
LOW LOW NO MARGIN
LOW HIGH MARGIN UP
HIGH LOW MARGIN DOWN
HIGH HIGH NO MARGIN