Ap3156, Serial digital interface – Diodes AP3156 User Manual
Page 11
AP3156
HIGH EFFICIENCY 1X/1.5X/2X CHARGE PUMP
FOR WHITE LED APPLICATIONS
AP3156 Rev. 1
11 of 15
SEPTEMBER 2009
©
Diodes Incorporated
SDI Command Timing Protocol
For the SDI command to be successfully received by the AP3156, all SDI timing specifications must be satisfied.
When no command is being sent, the SDI pin should be held High. If the SDI pin goes Low and stays Low for a time length between
T
SLO
(min) and T
SLO
(max) and then goes High and stays High for the length between T
SHI
(min) and T
SHI
(max), one falling edge is
registered by the AP3156. The total number of falling edges registered before the SDI pin is held High for longer than the maximum
separation time T
SEP(max)
identifies the command that has been received by the AP3156. The next series of falling edges before
another separation time of T
SEP
represents the next command. In other words, the AP3156 counts the number of consecutive falling
edges on the SDI pin and a different number represents a different command.
Each command is executed after it is successfully received. If at any time the SDI pin is held Low for longer than the maximum chip
disable time T
OFF(max)
, then the AP3156 will be turned off and enters the shutdown mode. Setting the SDI pin switching from Low to High
will re-enable the AP3156 and leave the shutdown mode. If the SDI pin is held on for a time duration over T
SEP
, then an end of a
sequence (EOS) occurs with a number of pulse conformed to specified timing.
A valid dual-sequence command occurs when one valid sequence is defined as an instruction, and the other is defined as data. Both
sequences have number of pulses less than 33. Also, a valid single-sequence command occurs when the sequence has number of
pulses greater than 32.
Channel 1 in
dimming control
T
SLO
T
SHI
T
SEP
SDI
Channel D2
1
2
9
10
8
2
1
Second Sequence
Channel D3
Channel D4
Channel D1
Channel Selection
Current Setting
Set Channel 1 to current level 2.
Channel D5
Channel D6
Channel 2 in
dimming control
Set Channel 2 to current level 2.
Channel 3 in
dimming control
Set Channel 3 to current level 2.
Channel 4 in
dimming control
Set Channel 4 to current level 2.
Channel 5 in
dimming control
Set Channel 5 to current level 2.
Channel 6 in
dimming control
Set Channel 6 to current level 2.
First Sequence
T
SEP
Figure 1: Dimming Control Selection (Dual-Sequence Command)
Serial Digital Interface