Analog Devices SCP-LT8604C-BEVALZ Demo Manual page 4

DEMO MANUAL SCP-LT8604C-BEVALZ
VOLTAGE INPUT-TO-OUTPUT CONTROL (VIOC)
IMPLEMENTATION
To implement the VIOC, set R19 = R13 = 0Ω and refer to
the configuration sheet for the VIOC for the V
age configuration values (set on the LDO board), and use
the following configuration for this board:
Table 3. VIOC Reference Designation
VIOC SETTING REFS
VOUT Refs
V − V = V
LDOIN LDOOUT VIOC

R
BOT
V 0.778V

( )
MAX LDOIN

I is the current through R
SINK
should be sized such that the divider current runs a mini-
mum of 100µA to minimize the I
4
LDOOUT
R R R
BOT TOP
R5 R4
 
R + R
BOT TOP
= 0.778V
 
R
 
BOT

+ +
R R
TOP MAX
+
I R

SINK MAX
R

BOT
, typically 15µA, so R
MAX
error term.
SINK
FREQUENCY PIN CONFIGURATION
The LT8604C allows the user to program an operating fre-
quency by a single resistor. The default operating fre-
volt-
quency is 2.0MHz. Note that changing the switching fre-
quency may affect other parameters and likely necessitate
a change in inductor and compensation component val-
ues. Contact the SCP team for applications support if
shifting the switching frequency greater than ±10%.
MAX
R8
Table 4. Resistor Selection Guide for Switching Frequency Setting
f
SW
200kHz
300kHz
400kHz
500kHz
600kHz
BOT
700kHz
800kHz
900kHz
1.00MHz
1.10MHz
1.20MHz
R2 (Ω) f
SW
221k 1.30MHz
143k 1.40MHz
110k 1.50MHz
86.6k 1.60MHz
71.5k 1.70MHz
60.4k 1.80MHz
52.3k 1.90MHz
46.4k 2.00MHz
40.2k 2.10MHz
36.5k 2.20MHz
33.2k
R2 (Ω)
30.1k
27.4k
25.5k
23.7k
22.1k
20.5k
19.1k
18.2k
16.9k
16.2k
Rev. 0