Table of Contents
SA572 stereo audio compander
Datasheet: https://www.alldatasheet.com/datasheet-pdf/pdf/18876/PHILIPS/SA572.html or https://www.onsemi.com/pdf/datasheet/sa572-d.pdf
Package
TL [Philips] SA572N HA [Logo] GGW1791 AN 9814nH ID
Topmark decodes as (per 2000 Philips Quality Manual, repeated at https://www.dutchaudioclassics.nl/TDA1541-Product-manufacturing-codes-and-markings/):
- Commercial part number: SA572N (SA572, 16-pin dual in-line package)
- Diffusion lot GGW17, assembly sequence 91
- Date of manufacture 1998, week 14. Diffused at Philips Semiconductors Nijmegen (H), assembled in Bangkok (n)
Later parts carry the more recent (~2000) Philips line-3 topmark format of YYWWDAR – Year, Week, Diffusion, Assembly, (centre of) Responsibility. These later parts usually indicate “centre of responsibility” being Sunnyvale, i.e. Signetics. This matches up with the Philips datasheet indicating that this is a Signetics part.
Decap
Decap took three attempts.
- First: rosin decap left residue stuck to the die surface.
- Second: Blowtorch caused thermal damage to the die.
- Third: rosin decap with hotter boil successfully decapped the chip.
Die
Circuit analysis notes
- The circuit is mirrored roughly down the centre.
- A 2.5V bandgap voltage reference is shared by both channels. This is likely the non-quite-symmetrical centre section.
- Bipolar process with extensive use of polysilicon resistors
The SA571 is a mono version of this chip. A SPICE model is available from jorg on the Mod Wiggler forums, including a transistor-level schematic. This may make it easier to follow the circuitry on the IC.