TLC5970 Datasheet, PDF (36/48 Pages) Texas Instruments – 3-Channel, 12-Bit, PWM LED Driver with Buck DC/DC Converter and Differential Signal Interface

TLC5970
SBVS140 – MARCH 2010
www.ti.com
EEPROM1 and EEPROM2 Write Data Latch
Each data latch bit length is 36 bits. The EEPROM1 write data latch sets the buck converter maximum on-duty
ratio, VFB target voltage, and the EEPROM differential interface mode. The EEPROM2 write data latch is used
to set the EEPROM DC default value.
EEPROM1 Write Data Latch (Register Address = 1100b)
The data bit assignments of the EEPROM write data latch 1 are shown in Table 11 and Figure 29.
BIT NUMBER
2-0
7-3
9-8
13-10
27-14
35-28
Table 11. EEPROM1 Write Data Latch Bit Assignment
BIT NAME
ONDUTY
FBVOLT
DSIMOD
LATTIM
—
WRCMD1
DESCRIPTION
PH on-duty (data = 0h to 7h, factory default = 0h)
FB target voltage (data = 00h to 1Fh, factory default = 00h)
Differential signal interface (DSI) timing mode (data = 0h to 3h, factory default
= 0h)
Internal latch generation delay time (data = 0h to Fh, factory default = Fh)
No EEPROM bits (14-bit data). The data cannot be stored in these bits even
if data are written to these bits.
Write command. When data are written to the EEPROM1 write data latch,
these data must be A5h (10100101b).
EEPROM1 Write Data Latch
MSB
35
28
27
14
13
10
9
8
7
LSB
3
2
1
0
Write
Write
No
No
Latch
Latch
DSI
¼ ¼ ¼ _Command
Command EEPROM
EEPROM Delay Time
Delay Time Timing
DSI FB Target
FB Target PH on PH on PH on
¼ _{Timing Voltage}
Voltage Duty Data Duty Data Duty Data
Bit 7
Bit 0
Bit 13
Bit 0
Bit 3
Bit 0 Mode Bit 1 Mode Bit 0 Data Bit 4
Data Bit 0 Bit 2
Bit 1
Bit 0
Figure 29. EEPROM1 Write Data Latch Bit Assignment
Maximum On-Duty Data for Buck Converter
The TLC5970 buck converter always operates with the Pulse Frequency Modulation (PFM) mode. Therefore, the
PH on-duty should be set to the value calculated by Table 12 to avoid inductor current saturation at the inductor.
ON-DUTY DATA (Binary)
000
001
010
011
100
101
110
111
Table 12. Maximum On-Duty Selection Truth Table
ON-DUTY DATA (Decimal)
0
1
2
3
4
5
6
7
ON-DUTY DATA (Hex)
0
1
2
3
4
5
6
7
ON-DUTY AT PH (%, Typical)
18
30
42
55
67
80
86
86
36
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