TLC5926-Q1_16 Datasheet, PDF (18/36 Pages) Texas Instruments – TLC592x-Q1 16-Channel Constant-Current LED Sink Drivers

TLC5926-Q1, TLC5927-Q1
SLVS973A – SEPTEMBER 2009 – REVISED JULY 2015
www.ti.com
9.4.1 Operation Mode Switching
In order to switch between its two modes, TLC592x-Q1 monitors the signal OE(ED2). When a one-clock-wide
pulse of OE(ED2) appears, TLC592x-Q1 enters the two-clock-period transition phase, the Mode Switching
phase. After power on, the default operation mode is the Normal Mode (see Figure 13).
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 13. Mode Switching
As shown in Figure 13, once a one-clock-wide short pulse (101) of OE(ED2) appears, TLC592x-Q1 enters the
Mode Switching phase. At the fourth rising edge of CLK, if LE(ED1) is sampled as voltage high, TLC592x-Q1
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.
NOTE
1. The signal sequence for the mode switching may be used frequently to ensure that
the TLC592x-Q1 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.
9.4.2 Normal Mode Phase
Serial data is transferred into TLC592x-Q1 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 TLC592x-Q1 to switch the operation mode. However, as long as LE(ED1) is high in the Mode Switching
phase, TLC592x-Q1 remains in the Normal mode, as if no mode switching occurred.
9.4.3 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.
9.4.3.1 Reading Error Status Code in Special Mode
When OE(ED2) is pulled low while in Special mode, error detection and load error status codes are loaded into
the Shift Register, in addition to enabling output ports to sink current. Figure 14 shows the timing sequence for
error detection. The 0 and 1 signal levels are sampled at the rising edge of each CLK. At least three zeros must
be sampled at the voltage low signal OE(ED2). Immediately after the second 0 is sampled, the data input source
of the Shift Register changes to the 16-bit parallel Error Status Code register, instead of from the serial data on
SDI. Normally, the error status codes are generated at least 2 μs after the falling edge of OE(ED2). The
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