WACOM W6005S Tablet RX Analog Front End ASIC
This is an analog front end ASIC used in the early WACOM ArtPad and Intuos series tablets. It contains a programmable gain amplifier (PGA), two mixers, and two integrators (opamps with the positive input tied to VREF) to perform the quadrature demodulation of the FM signal received from the pen. The integration capacitors and reset switches are external to the chip.
Intuos 3:

Pinout
| Pin | Name | Description |
|---|---|---|
| 1 | VCNT | Gain control |
| 2 | GND | Ground |
| 3 | VREF | Internal reference voltage, 1/2 VDD |
| 4 | VCC | Supply |
| 5 | MOE | Mixer output enable |
| 6 | MIN1 | Mixer 1 input |
| 7 | MC1 | Mixer 1 clock |
| 8 | MOUT1 | Mixer 1 output |
| 9 | SIN1 | Integrator 1 input |
| 10 | SOUT1 | Integrator 1 output |
| 11 | SOUT2 | Integrator 2 output |
| 12 | SIN2 | Integrator 2 input |
| 13 | MOUT2 | Mixer 2 output |
| 14 | MC2 | Mixer clock 2 |
| 15 | MIN2 | Mixer 2 input |
| 16 | FOUT | Unknown, connected to FIN |
| 17 | FIN | Unknown, connected to FOUT |
| 18 | VOUT | PGA output |
| 19 | VIN- | PGA input - |
| 20 | VIN+ | PGA input + |
References
- https://fccid.io/HV4GD0405U GD-0405 Schematics
- EP0967566A2, Figure 27