There are two hardware models of the TI Keyboard for graphing calculators: one with production codes listed on the back of the format F-MMYY and one without. The ones without contain a PCB branded with Silitek and the ones with TI-KEYBOARD-8. See Teardown of the TI-Keyboard over on the Cemetech forums for pictures and more details about the keyboard matrix.
The two hardware models appear to use the same schematic, with the only exception that the newer TI-KEYBOARD-8 model uses EM78P451S (PDF) instead of EM78P451 (PDF).
Full schematic of the PCB is included in this repository as Silitek Rev 1 PDF or KiCad
Below is a picture of the Silitek PCB including ping annotation and top and bottom routing.
| RefDes | Marking | Datasheet | Description |
|---|---|---|---|
| F1 | 500mA | - | Littlefuse 500mA power fuse |
| D4 | 3F | CH461F | Power diode |
| C3 | 10/16V | - | Bypass cap |
| CN1 | - | - | Keyboard matrix row connector |
| CN2 | - | - | Keyboard matrix col connector |
| U2 | EM78P451AQ | EM78P451 | ELAN EM78 series microcontroller |
| C4 | - | - | Bypass cap |
| C5 | (not pop.) | - | External oscillator C |
| R3 | 273 | - | 27kΩ external oscillator R |
| R4 | 331 | - | 330Ω LED current limiting R |
| R7 | 103 | - | 10kΩ /INT pin pullup |
| R8 | 103 | - | 10kΩ I/O pin pullup |
| D2 | - | - | Caps-Lock green LED |
| J2 | - | - | Graph link 2.5mm 3 conductor jack |
| R5/R6 | 103 | - | Graph link pullup for J2 |
| L4/L6 | - | - | Graph link L/C filter for J2 |
| C6/C7 | - | - | Graph link L/C filter for J2 |
| D3 | D3G | RB471E | Graph link diodes for J2 |
| U3 | H8 | IMH8A | Graph link NPN transistors for J2 |
| L5 | - | - | Graph link GND inductor for J2 |
| J1 | (not pop.) | - | Graph link 2.5mm 3 conductor jack |
| R1/R2 | (not pop.) | - | Graph link pullup for J1 |
| L1/L2 | (not pop.) | - | Graph link L/C filter for J1 |
| C1/C2 | (not pop.) | - | Graph link L/C filter for J1 |
| D1 | (not pop.) | - | Graph link diodes for J1 |
| U1 | (not pop.) | - | Graph link NPN transistors for J1 |
| L3 | (not pop.) | - | Graph link GND inductor for J1 |