TM1620 LED chip pin-out

14 June 2026
After figuring out the Titan Microelectronics TM1637 I also obtained other chips within the same general family and one of these is the TM1620. Unlike the other chips the data-sheet for this one was only in Chinese or rather dubious machine translations but it was similar enough to the other data-sheets that I was able to work things out via a combination of familiarity and experimentation, and the purpose of this article is purely documentation of the specifics of the chip so that the information is at hand should it ever end up being selected for a project of mine.

TM1620 test circuit

Compared to the TM1637 the polarity of the segment and grid pins is swapped with the former being anode connections and the latter cathode, in other words common-cathode, and two of the six grid pins can be reconfigured as extra segments. There is also a third serial communications pin that that the TM1637 does not have which I think could be used as a chip-select to drive multiple units. However as a trade-off the TM1620 does not have any button input capability.

TM1620 pin-out

Below is a reproduction of the pin-out from the data-sheet for the TM1620. Compared to the TM1637 the most notable difference is Pin 1 being ground rather than V_cc which is odd as almost all other pins that appear on both chips are either in the same place or the place next to it. Having the segment and grid pins in order and almost in one contiguous block is a nice touch. Pins 10 and 11 can be independently configured either as segments or grids.

Serial			LED common		Ground	LED common		Ground	Seg 14 Grid 5
STB	CLK	DIO	Grid 1	Grid 2	Ground	Grid 3	Grid 4	Ground	Seg 14 Grid 5
20	19	18	17	16	15	14	13	12	11
1	2	3	4	5	6	7	8	9	10
V_cc	Seg 1	Seg 2	Seg 3	Seg 4	Seg 5	Seg 6	Seg 7	Seg 8	Seg 13 Grid 6
V_cc	LED segments (anode)								Seg 13 Grid 6

Command protocol

Whereas the TM1672 used a protocol that resembles I²C the TM1620 instead has a third control wire named STB which I think stands for Start Transmit Bit as this pin is used to signal the start and end of a command transmission. Getting my existing TM1637 firmware working can be summed up as changing the start and stop to set this STB pin high/low instead of pulling/releasing clock/data, and removal of acknowledgement handling from byte transmission. Note that in this case a restart is simply a stop followed by a start. Since there is no situation with this chip where the clock/data line is read it should be possible to dispense with the pull-up resistors and instead drive the communication lines directly rather than using a pseudo open-drain setup.

Command set

Below is a condensed and simplified command set that shows the command combinations that are of practical use with the TM1720, with things such as test mode and the presumably-unimplemented key-scan reading excluded. Aside from some commands that other chip-sets have but are not implemented here, and conversely commands here that other chip-sets do not implement, this command set has been the same on all TM16xx data-sheets I have read so far.

Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0	Function
0	0	Unused (set to zero)				0	0	Use Seg 13 & Seg 14
						0	1	Use Seg 13 & Grid 5
						1	0	Use Grid 6 & Grid 5
0	1	Unused (set to zero)		0	0	0	0	Enable address auto-increment
0	1	Unused (set to zero)		0	1	0	0	Disable address auto-increment
1	0	Unused (set to zero)			0	0	0	Set pulse width 1/16
					0	0	1	Set pulse width 2/16
					0	1	0	Set pulse width 4/16
					0	1	1	Set pulse width 10/16
					1	0	0	Set pulse width 11/16
					1	0	1	Set pulse width 12/16
					1	1	0	Set pulse width 13/16
					1	1	1	Set pulse width 14/16
				0	One of above			Display off
				1	One of above			Display on
1	1	Unused (set to zero)		Address (0x0 – 0xb)				Set display address

After issuing set display address which is byte value 0b1100xxxx the segment data is transmitted using the mapping in the next section.

LED data memory layout

Each byte pair corresponds to the segments that are lit on a grid and the grids are done in order, as summerised in the table below. This differs from the TM1637 which only has a single byte per grid, and the presence of unused bits is due to the same protocol being used on other chips within the family that have more segments available.

	First byte								Second byte
	Bit 0	Bit 1	Bit 2	Bit 3	Bit 4	Bit 5	Bit 6	Bit 7	Bit 0	Bit 1	Bit 2	Bit 3	Bit 4	Bit 5	Bit 6	Bit 7
Grid 1 (0x00)	Seg1	Seg2	Seg3	Seg4	Seg5	Seg6	Seg7	Seg8	Unused				Seg13	Seg14	Unused
Grid 2 (0x02)
Grid 3 (0x04)
Grid 4 (0x06)
Grid 5 (0x08)
Grid 6 (0x0a)

Remarks

At first I thought that the STB serial line was just a chip-enable but I then realised upon re-reading the data-sheet that the wire-line protocol is different, and actually prefer it to the corrupted variant of I²C that the TM1637 uses. Experimenting with this chip was a one-day project that was limited to getting the chip working, so doing things like checking whether it was possible to drive multiple chips via common serial/clock lines has been left for a future project as this will require a potentially major firmware rewrite rather than just a bit of hacking. This future project will use the TM1668 since from what I have read about it so far it seems to be a more useful chip.