ak4184a AKM Semiconductor, Inc., ak4184a Datasheet - Page 28

• Manufacturer Part Number: ak4184a
• Description: Tsc With Keypad Scanner And Gpio Expander
• Manufacturer: AKM Semiconductor, Inc.

■
The AK4184A contains an oscillator and a PWM control circuit for controlling the brightness of an LED by
modulating the “on” time. The brightness is determined by the PWM basic frequency (f
PWM block divides the internal oscillator frequency (fosc) and modulates this output. The range of PWM frequency
(fpwm) is 80Hz minimum. The modulating range is provided by 32 duty cycle steps from the PWM logic controller.
The output control is determined by the PACT bit. The duty cycle width of the PWM frequency is controlled by the
BRV and DIV bits. The PWM signal stays constant on normal mode until duty cycle, PWM frequency changed.
The output type is possible to select either CMOS or Open Drain, set by the LPU bit. After reset, the PWM block is in
power-down state and the BRCONT pin outputs a “L” level.
Example BRV [4:0] =11H setting
■ PWM Control Register (PAGE 1)
Addr
MS0947-E-00
18H
Internal
PWM
Counter
LED contrast control
BRCONT
PWMCTRL
14:13
12:8
Bits
Name
5:3
2:0
15
7
6
0
PACT
Name
BRV
LPU
DIV
Oscillator
1
MSB
LPU
D15
2
Output type Open drain / CMOS
Reserved
Bright Control Value
The period of “H” output level is (control value + 1) cycle in unit of (fpwm/32)
Reserved
Oscillator and PWM Logic Controller Power Up
Reserved
PWM clock divider index
D14
3
0
0: CMOS type (default)
1: Open Drain type
0: Power Down State (default)
1: Normal mode (Oscillator power up and enable output)
fpwm(typ.)=fosc/2
8
f
osc
Duty Cycle BR[4:0] =11H
PWM frequency(f
D13
0
9
Table 35. PWM Control Register Format
10
Figure 17. PWM output waveform
2
Table 36. PWM Control Register
Divider
D12
(DIV[2:0]+7)
Figure 16. PWM output block
11
12 13 14
D11
[DIV + 7]
BRV[4:0]
pwm
D10
- 28 -
) = fosc / 2
f
pwm
15
D9
Description
16 17
PWM Logic
(DIV[2:0]+7)
Controller
D8
18
D7
0
8
PACT
D6
24 25
f
brcont
D5
pwm
0
26
BRCONT
) and duty cycles. The
27
D4
0
28
D3
0
29 30
D2
[AK4184A]
DIV[2:0]
2008/04
31
D1
0
LSB
D0