Advertisement
CONFIGURATION SETTINGS
Demonstration circuit SCP-LT3461-EVALZ features the
LT3461 in a 12V output boost converter which operates
from an input voltage of 3V to 6V. The maximum output
current is 70mA when powered from a 5.0V input and
40mA when powered from a 3.3V input.
The output of the SCP-LT3461-EVALZ is resistor-program-
mable from 5V to 38V. The board can be also configured
to drive VIOC-capable linear regulators.
OUTPUT VOLTAGE PROGRAMMING
R1
⎛
⎞
= 1 .2 5 5 V 1 +
V
⎝ ⎜
⎠ ⎟
OUT
R2
Table 2. Resistor Selection Guide for Common Output Voltages
V
(V)
OUT
5.0
6.0
7.0
8.0
9.0
10.0
11.0
12.0
13.0
14.0
15.0
16.0
17.0
18.0
19.0
20.0
21.0
22.0
23.0
24.0
25.0
30.0
35.0
38.0
DEMO MANUAL SCP-LT3461-EVALZ
R1 (Ω)
R2 (Ω)
45.3k
15.0k
61.9k
16.5k
84.5k
18.7k
102k
19.1k
140k
22.6k
191k
27.4k
221k
28.7k
261k
30.1k
274k
29.4k
287k
28.0k
301k
27.4k
316k
26.7k
332k
26.7k
348k
26.1k
365k
26.1k
383k
25.5k
402k
25.5k
422k
25.5k
442k
25.5k
464k
25.5k
487k
25.5k
536k
23.2k
634k
23.7k
681k
23.2k
SHDN PIN CONFIGURATION
The SHDN pin is tied to the optional SCP Run/Sequence
header P1. To create a harness for this function, use Molex
part 0510650300 with crimp pin 50212-8000.
To use an active run signal, use a 1.00M resistor for either
pull-up or pull-down resistors R4 and R5, short R6 with
0W, and use the drive signal from connector P1.
VOLTAGE INPUT-TO-OUTPUT CONTROL (VIOC)
IMPLEMENTATION
To implement the VIOC function for this regulator, set R7
to 0W. Refer to the "Configuration Settings" section in the
Demo Manual for the low-dropout (LDO) linear regulator
board and use the following configuration for this board.
Table 3. VIOC Cross-Reference Designators
VIOC SETTING REFERENCES
V
Reference Designators
OUT
V
− V
= V
= 1 .2 5 5 V
L DOIN
L DOOUT
VIOC
⎛
R
BOT
= 1 .2 5 5 V
V
(
)
⎝ ⎜
MAX
LDOIN
I
is the current through R
SINK
Since the divider current is fixed due to the internal low
side gain setting feedback resistor and is less than the rec-
ommended divider current of 100µA, the effect of the sink
current on the maximum linear regulator input voltage
cannot not be mitigated and should be taken into consid-
eration.
R
R
R
BOT
TOP
R2
R1
⎛
⎞
R
+ R
BOT
TOP
⎝ ⎜
⎠ ⎟
R
BOT
⎞
+ R
+ R
TOP
MAX
+ I
R
⎠ ⎟
SINK
MAX
R
BOT
which is typically 15µA.
MAX
MAX
R3
Rev. 0
3
Advertisement
