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AS1112

Datasheet - D e t a i l e d D e s c r i p t i o n

Power Dissipation

To ensure proper operation of the device, the total power dissipation of the AS1112 must be below the power dissipation rating of the device

package. Total power dissipation is calculated as:

Where:

VCC is the device supply voltage;

ICC is the device supply current;

VOUT is the device OUTn voltage when driving LED current;

IMAX is the LED current adjusted by RIREF;

DCn is the maximum dot correction value for OUTn;

n is the number of OUTn driving LED at the same time;

dPWM is the duty cycle defined by pin OEN or the greyscale PWM value.

Operating Modes

The AS1112 operates in two modes (see Table 10). Greyscale operating mode (see Figure 14 on page 13) and the shift registers are in reset

state at power-up.

Setting Dot Correction

The AS1112 can perform independent fine-adjustments to the output current of each channel, i.e., dot correction. Dot correction is used to adjust

brightness deviations of LEDs connected to the output channels (OUT0:OUT15).

The device powers up with the following default seetings: DC = 63 and GS = 4095.

The 16 channels can be individually programmed with a 6-bit word. The channel output can be adjusted in 64 steps from 0 to 100% of the maxi-

mum output current (IMAX). The output current for each OUTn channel can be calculated as:

Where:

IMAX is the maximum programmable output current for each output;

DCn is the programmed dot correction value for output (DCn = 0 to 63);

n = 0 to 15

Dot correction data are simultaneously entered for all channels. The complete dot correction data format consists of 16 x 6-bit words, which

forms a 96-bit serial data packet (see Figure 11). Channel data is put on one by one, and the data is clocked in with the MSB first.

Figure 11. Dot Correction Data Packet Format

Table 10. Operating Modes

Mode

Input Shift Register

Operating Mode

0

192-bit

Greyscale PWM Mode

1

96-bit

Dot Correction Data Input Mode

PD = (VCC x ICC) + (VOUT x IMAX x n x

DCn

63

(EQ 2)

dPWM)

IOUTn = IMAX x

DCn

63

(EQ 3)

DC0.0

DC0.5

DC1.0

DC14.5

DC15.0

DC15.5

LSB

DC OUT0

DC OUT14:DC OUT1

...

...

...

DC OUT15

MSB

95

90

89

6

5

0