AS1112
Datasheet - Detailed Description
Figure 8. Error Detection Timing (GS=FFFFHEX, DC=3FHEX
)
LD
>1µs
OEN
GSCLK
SID
LODn, LSDn
LODn+1, LSDn+1
Error
Detection
Start
Error
Detection
End
Note: The rising edge of LD latches new data into the internal registers depending on the logic level of the pin
MODE. If the pin MODE is tied GND, the greyscale registers are updated. If the pin MODE is tied to VCC, the
dot correction registers are updated.
Delay Between Outputs
The AS1112 uses graduated delay circuits between OUTn outputs. These circuits are contained in the constant-current
driver block of the AS1112 (see Figure 1 on page 1). The average-delay time is 30ns (typ).
The maximum delay is 450ns (typ) from OUT0 to OUT15. The delay scheme works by switching on and switching off
each output channel. Thus the on/off time of each channel is the same regardless of the delay. These delays prevent
large inrush currents and switching noise that can reduce bypass capacitance when the outputs are switched on.
OUTn Enable
All OUTn channels can be collectively switched off with one signal. When OEN is set to 1, all OUTn channels are dis-
abled, regardless of the device logic operations. The greyscale counter is also reset when OEN is set to 1.
When OEN is set to 0, all OUTn channels are in normal operation.
Table 10. Pin OEN Truth Table
OEN
OUT0:OUT15
Normal Operation
Disabled
0
1
Setting Maximum Channel Current
The maximum output current per channel is programmed by a single resistor, RIREF, which is placed between pin IREF
and GND. The voltage on pin IREF is set by an internal band gap VIREF (1.24V typ). The maximum channel current is
equivalent to the current flowing through RIREF multiplied by a factor of 31.5. The maximum output current is calculated
as:
VIREF
IMAX =
x 31.5
(EQ 1)
RIREF
Where:
VIREF = 1.24V;
RIREF = User-selected external resistor.
Figure 5 on page 7 shows the maximum output current IOUT versus RIREF, where RIREF is the value of the resistor
between IREF terminal to GND, and IOUT is the constant output current of OUT0:OUT15.
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