M66503 View Datasheet(PDF) - MITSUBISHI ELECTRIC

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Description

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M66503

16-BIT CONSTANT CURRENT LED DRIVER with SHIFT REGISTER AND LATCH

MITSUBISHI ELECTRIC  

MITSUBISHI 〈DIGITAL ASSP〉

M66503ASP/AGP

16-BIT CONSTANT CURRENT LED DRIVER with SHIFT REGISTER AND LATCH

OPERATION

1. LED Drive Current Settings

The M66503A has an internal power supply, which pro-

vides a constant current to each bit output. The output

value of the constant current is set by means of a load re-

sistor, RC,connected between the RC pin and GND and is

approximated by the equation below.

IO (Qn) =5·VCC/(2·RC +100)

2. Switching Operation

If the output data of the latch is “H”, LED lights up. The

value of the LED drive current is IO(Qn). If the output data

of the latch is “L”, LED goes off, and the LED drive current

becomes nearly zero, irrespective of the value of IO(Qn).

3. How to Use the OEA and OEB Inputs

If OEA = “L” and OEB = “L”, all output currents are turned

off. Accordingly, it is possible to prevent a large current

from flowing through LESs by, for example, fixing both

OEA and OEB to “L” until VCC, after turned on, reaches a

steady state. If OEA =“H”, all output currents turn on. This

function facilitates the checking of LEDs for failure. When

OEA =“L” and OEB =“H”, each output current turns on and

off according to the output data of the latch.

4. VCC and GND Pins

Pins related to the power supply function are VCC and

GNDs 1-5 (GNDs 1-3 for the M66503AGP). The role of

these pins in terms of the internal circuits are as follows.

VCC

: commonly used by both digital and

analog circuits

GND 1

: used by digital circuits

GNDs 2-5 (2-3) : used by analog circuits

In practical wiring, the following should be noted.

(1) Secure as much width as possible for conductors and

avoid lengthy wiring.

(2) Allocate electrolytic capacitors for stable voltage near VCC

and GNDs 2-5 (2-3).

(3) Allocate by-pass capacitor near VCC and GND1.

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