PCA84C441 datasheet(10/40 Pages) PHILIPS

10 / 40 page

1996 Nov 29

Philips Semiconductors

Product speciﬁcation

8-bit microcontrollers with OSD and VST

84C44X; 84C64X; 84C84X

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

⁄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:

Where:

•

• PWMDL is the decimal value of the contents of the

PWM data latch.

Therefore, the analog output voltage is:

HIGH

--------------

HIGH

PWMDL

HIGH time of the PWM pulse

repetition time of the PWM pulse

XTAL

--------------

PWMDL

------------------------

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

handbook, full pagewidth

MCD176

DP0.x data

I/O

DP0.x/PWMx

6-BIT PWM DATA LATCH

P6LVL

PWMnE

6-BIT DAC PWM

CONTROLLER

polarity control bit

f PWM

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