MC14489 データシートの表示（PDF） - Motorola => Freescale

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MC14489

Multi-Character LED Display/Lamp Driver

Motorola => Freescale 

a through h (Pins 1, 2, 4 – 7, 19, 20)

Anode–Driver Current Sources. These outputs are close-

ly–matched current sources which directly tie to the anodes

of external discrete LEDs (lamps) or display segment LEDs.

Each output is capable of sourcing up to 35 mA.

When used with lamps, outputs a, b, c, and d are used to

independently control up to 20 lamps. Output h is used to

control up to 5 lamps dependently. (See Figure 17.) For

lamps, the No Decode mode is selected via the configuration

register, forcing e, f, and g inactive (low).

When used with segmented displays, outputs a through g

drive segments a through g, respectively. Output h is used to

drive the decimals. If unused, h must be left open. Refer to

Figure 10.

Bank 1 through Bank 5 (Pins 9, 13, 15, 16, 17)

Diode–Bank FET Switches. These outputs are low–resis-

tance switches to ground (VSS) capable of handling currents

of up to 320 mA each. These pins directly tie to the common

cathodes of segmented displays or the cathodes of lamps

(wired with cathodes common).

The display is refreshed at a nominal 1 kHz rate to achieve

optimum brightness from the LEDs. A 20% duty cycle is uti-

lized.

Special design techniques are used on–chip to accommo-

date the high currents with low EMI (electromagnetic interfer-

ence) and minimal spiking on the power lines.

POWER SUPPLY

VSS (Pin 14)

Most–negative supply potential. This pin is usually ground.

Resistor Rx is externally tied to ground (VSS). Therefore,

the chip’s VSS pin does not contain the Rx current compo-

nent.

VDD (Pin 13)

Most–positive supply potential.

To guarantee data integrity in the registers and to ensure

the serial interface is functional, this voltage may range from

3 to 6 volts with respect to VSS. For example, within this volt-

age range, the chip could be placed in and out of the low–

power mode.

To adequately drive the LEDs, this voltage must be 4.5 to

6 volts with respect to VSS.

The VDD pin contains the Rx current component plus the

chip’s current drain. In the low–power mode, the current mir-

ror and clock oscillator are turned off, thus significantly re-

ducing the VDD current, IDD.

MOTOROLA

MC14489

7

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