PCF84C443 查看數據表（PDF） - Philips Electronics

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PCF84C443

8-bit microcontrollers with OSD and VST

Philips Electronics 

Philips Semiconductors

8-bit microcontrollers with OSD and VST

Product specification

84C44X; 84C64X; 84C84X

8 ANALOG CONTROL

8.1 6-bit PWM DACs

Five PWM outputs are available for analog control

purposes e.g. volume, balance, brightness, saturation, etc.

The block diagram of a typical 6-bit PWM DAC is shown in

Fig.8. Each PWM output can generate pulses of

programmable length that have a repetition frequency of

1⁄64 × fPWM, where fPWM = 1⁄3 × fXTAL.

8.1.1 PIN SELECTION FOR PWM OUTPUTS

The PWM outputs PWM1 to PWM5, share the same pins

as the Derivative Port lines DP0.1 to DP0.5.

Setting the (relevant PWM enable) bit PWMnE to:

• Logic 1, selects the relevant PWMx output function

• Logic 0, selects the relevant DP0.x Port function.

8.1.2 POLARITY OF THE PWM OUTPUTS

The polarity of all five PWM outputs is selected by the state

of the polarity control bit P6LVL.

Setting the control bit P6LVL to:

• Logic 0, sets the PWMx outputs to the default polarity

• Logic 1, inverts all the PWMx outputs.

8.1.3 ANALOG OUTPUT VOLTAGE

A DC voltage proportional to the PWM control setting may

be obtained by connecting an integrating network to each

of the PWM outputs (see Fig.9).

The analog value is calculated as follows:

VA = t--H----tI--Gr---H-- × VO

Where:

•

tHIGH = t0 × PWMDL = HIGH time of the PWM pulse

• tr = t0 × 64 = repetition time of the PWM pulse

• t0 = f--X----T3---A---L-

• PWMDL is the decimal value of the contents of the

PWM data latch.

Therefore, the analog output voltage is:

VA = --P----W---6---M-4----D----L-- × VO

handbook, full pagewidth

f PWM

6-BIT PWM DATA LATCH

Q

6-BIT DAC PWM

CONTROLLER

Q

DP0.x data

I/O

PWMnE

DP0.x/PWMx

P6LVL

polarity control bit

MCD176

1996 Nov 29

Fig.8 Block diagram of the 6-bit PWM DAC.

10

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