cxa2108q Sony Electronics, cxa2108q Datasheet - Page 14

• Manufacturer Part Number: cxa2108q
• Description: Constant-current Driver For Full Color Led Display
• Manufacturer: Sony Electronics

3. Drive current data (Dd)
Even when driving LEDs of the same color with the same current value, individual differences in characteristics
result in an uneven emitting intensity. In addition, the required current value also differs according to the
emitting color (RGB). That is to say, the necessary current differs for each LED. This drive current IOUT
corresponds to the amplitude of the IOUT output PWM waveform as shown in Fig. 1. The CXA2108Q can set
this current independently for each LED using Coarse Adj. (2 bits: D8, D9) and Fine Adj. (8 bits: D0 to D7). The
maximum drive current (Io (FFh): IOUT @ D0 to D7 = FFh) is set by Coarse Adj. (2 bits: D8, D9). The
minimum drive current (Io (00h): IOUT @ D0 to D7 = 00h) is approximately 1/2 of Io (FFh), and the range from
the minimum to the maximum drive current can be set at an accuracy of 8 bits (D0 to D7 = 256 steps).
Note that this drive current is generated using the Iref described in 6. as the reference.
The relationship between the Fine Adj. (8 bits: D0 to D7) data and the drive current, and the drive current data
(D0 to D9) to drive current correspondence table are shown below.
Luminance data (Dv)
1
D9
Drive current data (Dd)
Nv = Tv/T
0000000000
0000000001
0000000010
1000000000
1111111111
D7
D9 to 0
00000000 (00h)
10000000 (80h)
11111111 (FFh)
:
:
D7 to 0
Table 3. Relationship Between Luminance Data, Brightness Data and Emitting Duty
CLK
Fig. 2. Relationship Between Fine Adj. (8 bits: D0 to D7) Data and Drive Current
Table 4. Drive Current Data (D0 to D9) to Drive Current Correspondence Table
:
:
D0
= Dv
Brightness (D3 to 0) = 0000
D0
1023
512
Db
Nv
0
1
2
:
:
(Maximum drive current)
(Minimum drive current)
D9
400
600
800
0
Emitting duty [%]
:
:
Iref
Iref
Iref
Io (FFh)/2
D8
0.006
0.012
3.125
6.244
Io (FFh)
Io (00h)
0
0
Drive current
:
:
1200
1600
D9
800
0
0
00h
01h
Drive current
:
:
Iref
Iref
Iref
D8
Fine Adj. (8 bits: D0 to D7) data
1
Brightness (D3 to 0) = 0111
– 14 –
1200
1800
2400
D9
1
Nv
• •
4096
8184
Nv
16
0
8
1
:
:
:
:
(256 steps)
1 LSB
= (Io (FFh)
and emitting duty
D8
Iref
Iref
Iref
– Io (00h))/255
0
1600
2400
3200
D9
1
Emitting duty [%]
• •
0.049
0.098
25.00
49.95
:
:
0
:
:
FEh
Iref
Iref
Iref
D8
1
FFh
Maximum drive current Io (FFh)
Minimum drive current Io (00h)
Brightness (D3 to 0) = 1111
16368
8192
Nv
16
32
0
:
:
Emitting duty [%]
0.098
0.195
50.00
99.90
CXA2108Q
0
:
: