Fujitsu ASSP Product
7/14
Power Management
MB39C026 Evaluation Board
8. Initialization
8. Initialization
(
)
(
)
V
2
1
=
k
100
k
100
+
k
300
×
V
3
0
=
6
R
6
R
+
5
R
×
ref
V
=
1
VO
.
.
Ω
Ω
Ω
FB 6
VO1
R5-2
0R
R5-1
300k
or
499k
C3
22pF
R6
100k
C2
4.7uF
(1)
Output Voltage Setting
EN1
Set EN1 to VIN to start the buck DC/DC converter (VO1). R1 pull-down EN1 to
GND and disable VO1 if EN1 has no input.
EN2
Set EN2 to VIN to start the LDO converter (VO2). R2 pull-down EN2 to GND
and disable VO2 if EN2 has no input.
Power On Reset (POR)
R3 and R4 are the pull-up resistors for POR (Pin 4). A 1M
resistor is required
to placed at either R3 or R4. When R3 has a 1M
resistor and R4 is open; the
POR will be connected VIN. When R4 has a 1M
resistor and R3 is open; the
POR pin will be connected to VO1.
By default, only R3 require a 1M
resistor while R4 is open.
(2)
Input Signal Setting
(
)
(
)
1.8V
=
100k
100k
+
499k
×
0.3V
=
R6
R6
+
R5
×
ref
V
=
VO1
The output voltage of VO1 can be adjusted by
the external resistor divider.
As illustrated below: