TLC5926 Datasheet, PDF (16/29 Pages) Texas Instruments – 16-CHANNEL CONSTANT-CURRENT LED SINK DRIVERS

TLC5926, TLC5927
SLVS677 – JULY 2008 ....................................................................................................................................................................................................... www.ti.com
Operation Phases
Operation Mode Switching
In order to switch between its two modes, TLC5926/TLC5927 monitors the signal OE(ED2). When a
one-clock-wide pulse of OE(ED2) appears, TLC5926/TLC5927 enters the two-clock-period transition phase, the
Mode Switching phase. After power on, the default operation mode is the Normal Mode (see Figure 12).
Switching to Special Mode
Switching to Normal Mode
1
2
3
4
5
CLK
1
2
3
4
5
CLK
OE(ED2) ¹
0
1
1
1
OE(ED2) ¹
0
1
1
1
LE(ED1) ⁰
0
0
1
0
LE(ED1) ⁰
0
0
0
0
Actual Mode
Mode
Special
Phase _{(Normal or Special) Switching Mode}
Actual Mode
Mode
Normal
Phase _{(Normal or Special) Switching Mode}
Figure 12. Mode Switching
As shown in Figure 12, once a one-clock-wide short pulse (101) of OE(ED2) appears, TLC5926/TLC5927 enters
the Mode Switching phase. At the fourth rising edge of CLK, if LE(ED1) is sampled as voltage high,
TLC5926/TLC5927 switches to Special mode; otherwise, it switches to Normal mode.The signal LE(ED1)
between the third and the fifth rising edges of CLK cannot latch any data. Its level is used only to determine into
which mode to switch. However, the short pulse of OE(ED2) can still enable the output ports. During mode
switching, the serial data can still be transferred through SDI and shifted out from SDO.
NOTES:
1. The signal sequence for the mode switching may be used frequently to ensure that the TLC5926/TLC5927 is
in the proper mode.
2. The 1 and 0 on the LE(ED1) signal are sampled at the rising edge of CLK. The X means its level does not
affect the result of mode switching mechanism.
3. After power on, the default operation mode is Normal mode.
Normal Mode Phase
Serial data is transferred into TLC5926/TLC5927 via SDI, shifted in the Shift Register, and output via SDO.
LE(ED1) can latch the serial data in the Shift Register to the Output Latch. OE(ED2) enables the output drivers to
sink current. These functions differ only as described in Operation Mode Switching, in which case, a short pulse
triggers TLC5926/TLC5927 to switch the operation mode. However, as long as LE(ED1) is high in the Mode
Switching phase, TLC5926/TLC5927 remains in the Normal mode, as if no mode switching occurred.
Special Mode Phase
In the Special mode, as long as OE(ED2) is not low, the serial data is shifted to the Shift Register via SDI and
shifted out via SDO, as in the Normal mode. However, there are two differences between the Special Mode and
the Normal Mode, as shown in the following sections.
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