Specifications
| Type | Bidirectional logic level converter, one MOSFET per channel, no direction or enable pin |
|---|---|
| Channels | 6: L1 to L6 on the 3.3 V side, each opposite H1 to H6 on the 5 V side |
| Transistors | BSS138, gate on 3V3; switches on from 0.8 to 1.6 V on its gate |
| Pull-ups | 10 kΩ on every pin: L pins to 3V3, H pins to 5V. None needed for I2C |
| Supply | 5V and GND only, from your board's 5 V pin (VBUS on a Pico) |
| 3V3 pin | An output: the regulator's 3.3 V, for a 3.3 V block in the socket. Never wire a board's 3V3 to it |
| Regulator | ME6211C33, 3.3 V ±2 %. Rated 500 mA, but from 5 V its 300 mW package limit comes at about 176 mA |
| Speed | A LOW crosses at once; a HIGH is finished by a 10 kΩ. Serial and I2C fine; SPI about 4 MHz on short wires |
| Socket | 8-way right-angle female, on the 3.3 V side: GND, 3V3, L1 to L6, GND on the square pad |
| Header | 8-pin right-angle male, on the 5 V side: GND, 5V, H1 to H6. Its square pad is H6 |
| Board | 22.4 × 30.4 mm, laid landscape with a connector on each long edge; two 4.8 mm LEGO holes 24 mm apart |
| In the box | 1 × TK97 block. It also ships in the TinkerBlock 46-piece kit |
What it does
It lets a 5 V board and a 3.3 V part share signals without the 5 V reaching the 3.3 V pins, in both directions, on six lines at once. A 5 V Uno can drive a 3.3 V display through it; a 3.3 V ESP32 can talk to a 5 V module.
Each channel is a BSS138 transistor with a 10 kΩ pull-up on each side. A LOW on either side pulls the other side LOW; at rest each side sits at its own HIGH. The board also carries an ME6211 regulator, which makes the 3.3 V side's supply from the header's 5V. That is the thing to know before wiring it: the socket's 3V3 pin is an output.
The page this replaces said four channels, named LV and HV pins the board does not have, and told you to wire the 3V3 pin to your 3.3 V device's supply, which on a 3.3 V microcontroller ties two regulators together.
Two things to know before wiring
- It needs 5V and GND, and nothing else. From a 3.3 V board that means its 5V pin, or VBUS on a Pico, to the header's 5V.
- Your board's 3V3 pin goes nowhere. A 3.3 V block in the socket takes its power from the TK97's 3V3.
Wiring, in four lines
- GND to your board's GND.
- 5V on the header to your board's 5V, or VBUS on a Pico.
- A 5 V board (an Uno): its signals on H1 to H6, the 3.3 V block in the socket.
- A 3.3 V board (an ESP32, an ESP32-S3, a Pico): its signals on L1 to L6, the 5 V part on H1 to H6.
Where to start
The handbook below is nine short articles, each with a working figure. The two rows is the pinout, and the 3V3 pin is an output the wiring rule. A 5 V board and a 3.3 V block and a 3.3 V board and a 5 V part are the two builds, each with a sketch that proves the wiring. If nothing crosses, when nothing crosses.
For the 27-pack of loose converters and the TXB0108 and TXS0108 boards, see the logic level converter handbook.
When it doesn’t work
- Where do I connect the 3V3 pin?
- To a 3.3 V block's VCC, which a block plugged into the socket does by itself, and to nothing else. It is the output of the TK97's own regulator. On a 3.3 V board such as an ESP32 or a Pico, leave the board's 3V3 pin off it and wire the board's 5V (VBUS on a Pico) to the header's 5V.
- Does it need 3.3 V as well as 5 V?
- No. Only 5V and GND. The regulator on the board makes the 3.3 V side's supply from 5V; without 5V, neither side works.
- How many channels, and which way do they go?
- Six, and each works both ways with no direction pin: a LOW on either side pulls the other side LOW, and each side's 10 kΩ makes its own HIGH. I2C, where the two ends take turns, works through it.
- Is it fast enough for SPI?
- For a few MHz on short wires, yes: an Uno driving a TK89 display through it is the owner's own wiring. Past that, a HIGH made by a 10 kΩ runs out of time, faster in the 5 V to 3.3 V direction than the other. Slow the clock first.
- How much can a block in the socket draw?
- About 176 mA from a 5 V supply before the regulator's package passes its 300 mW rating, though the data sheet's front page says 500 mA. A sensor or an I2C block takes a few milliamps.
- How is it different from the logic level converters in the 27-pack?
- The channels are the same circuit. The 27-pack's boards have LV and HV pins that you feed yourself; the TK97 takes only 5V and makes its own 3.3 V, and has a socket a 3.3 V block plugs into. The llc handbook covers the 27-pack and the TXB0108 and TXS0108 boards.
