Table of Contents
Advertisement
Outline of Operations
(1) Power Switch, DC/DC Block
VC
VCON
33uF
As shown in Truth Table 1, in the power switch, the VB1 and VB2 voltages are output to the VB terminal by the combination
of D0 and D1. The power MOS making up the switch has an approximately 0.2 Ω ON resistor which can output current up to
600 mA. However, as this power MOS also incorporates a parasitic PN junction diode from the source to the drain, the VB2
voltage must be higher than VB1–0.5V.
The DC/DC section can be combined with MPC1830 to construct a switching regulator. MPC1830 determines the operation
mode while monitoring VB1, VB2, and the output voltage VC, and outputs the voltage as D0 and D1. By the combination of
D0 and D1, the operations of the power-MOSFET are set as shown in Truth Table 2. "PWM" and "PWMB" in the table
indicate outputs with the same phase and opposite phase with the 176 kHz PWM signal input to the PWM terminal are
obtained respectively. a 176 kHz, duty 70% fixed pulse is also output
to the L2L terminal.
Truth Table 1 (Power Switch)
D0
D1
M1
L
OFF
L
L
H
ON
H
L
OFF
H
H
OFF
Truth Table 2 (Power Switch)
D0
D1
M7
L
L
OFF
L
H
PWMB
H
L
OFF
H
H
OFF
VB
PWM
AM3
Li+
10uH
47uH
GND
GND
GND
Fig. 1 Power Switch, DC/DC Section
M2
VB
OFF
Z
OFF
VB1
ON
VB2
ON
VB3
M3
M8, 9
L1
OFF
Z
OFF
OFF
PWM
PWMB
PWM
OFF
Z
PWM
PWM
OFF
Z
PWM
VG
D0
Slep-Up/Down
1
D1
72
/Power SW
71
Decoder
VG
M2
VB
Power SW
4
M1
Pre driver
VB
5
VB1
2
VB1
VG
3
M3
VB2
6
L2H
M4
7
Slep-Up/Down
8
DCC2
Pre driver
M6
L2L
9
M5
VO
10
VG
VO
M7
11
Slep-Up
L1
12
Pre driver
M8
13
DCC1
14
DCC1
L1
15
M9
M4
L2H
M6
M5
OFF
Z
OFF
OFF
OFF
Z
OFF
OFF
PWM
ON
OFF
PWM
70%
30%
— 67 —
L2L
Z
* Standby state
* Step-up
Z
VO
* Step-down
* Step-up/down
70%
Advertisement
Table of Contents
