SSC050-01 Datasheet, PDF (77/79 Pages) Maxim Integrated Products – Two-Wire Serial Backplane Controller

Electrical Characteristics
AC Characteristics
SSC050-01
Data Sheet
Optional External Tach Filter
The fan tach inputs of the SSC050-01 utilize schmitt trigger input buffers and are also internally
digitally filtered. However, excessive external noise on a tach input can result in inaccurate fan speed
current count values. The use of an external low pass filter along with the use of the extended tach filter
mode (Tach Filter Extend, bit 6 of register FDh) of the SSC050-01 will eliminate inaccurate current
count values. The following circuit provides excellent noise rejection at all possible RPM ranges
supported by the SSC050-01.
Vdd
Fan Tach Output
3.3K ohm
330 ohm
0.1 uF
SSC050-01
P2.4-P2.7
Vss
Figure 5-6. Optional External Tach Filter
Revision 4.0
November 10, 2004
5-10