LX7178 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA (800) 713-4113, (949) 380-6100
Page 6
Copyright
2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Recommended Operating Conditions
Description
Symbol
Min
Max
Unit
Input Voltage
V
IN
3
5.5
V
Output Current
I
OUT
5
A
Operating Ambient Temperature
T
A
0
85
°C
Enable Chip
EN
V
IN
Shut Down Chip
EN
Pull to GND
Enabling Regulator from I
2
C Bus
In addition to the EN pin, the regulator can be enabled and disabled via the I
2
C bus by
programming the control register. During disable, the regulator and most of the support circuitry
is turned off. However, the I
2
C bus circuitry is still active and maybe programmed.
Setting the Output Voltage
Using the I
2
C interface you can adjust VOUT from 0.6V to 1.2V. When I
2
C interface is
implemented, the reference voltage is programmed with the I
2
C bus VSEL register value.
Where N
SEL
is the decimal value of the 7 VSEL bits.
In case a higher output voltage is needed, it must be programmed through an external resistor
divider connected from SW to VOUT then to GND. For noise immunity, the lower resistor R2
from VOUT to GND should be greater than 100kΩ. The formula below calculates the value of
VOUT based on the resistor divider R1 & R2.
V
REF
is determined by the chip, for example, to set the LX7178-01CSP to a VOUT = 0.96V,
given V
REF
= 0.8V. First pick the lower resistor R
2
=150k, calculate the upper resistor R1=30.1k.
