TS2012FC View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
TS2012FC Datasheet PDF : 31 Pages
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Application information
TS2012FC
4.4
Low frequency response
If a low frequency bandwidth limitation is required, it is possible to use input coupling
capacitors. In the low frequency region, the input coupling capacitor Cin starts to have an
effect. Cin forms, with the input impedance Zin, a first order high-pass filter with a -3 dB cut-
off frequency (see Table 5 to Table 7):
FCL
=
---------------------1-----------------------
2 ⋅ π ⋅ Zin ⋅ Cin
So, for a desired cut-off frequency FCL, Cin is calculated as follows:
Cin = -2----⋅------π-----⋅------Z1---i--n----⋅------F----C---L-
with FCL in Hz, Zin in Ω and Cin in F.
The input impedance Zin is for the whole power supply voltage range and it changes with the
gain setting. There is also a tolerance around the typical values (see Table 5 to Table 7).
Figure 36. Cut-off frequency vs. input capacitor
Tamb=25°C
100
G=24dB
Zin=7.5kΩ typ.
10 G=18dB
Zin=15kΩ typ.
G=6dB, G=12dB
Zin=30kΩ typ.
1
0.1
1
Input Capacitor Cin (μF)
4.5
Decoupling of the circuit
Power supply capacitors, referred to as CS1 and CS2 are needed to correctly bypass the
TS2012.
The TS2012 has a typical switching frequency of 280 kHz and output fall and rise time about
5 ns. Due to these very fast transients, careful decoupling is mandatory.
A 1 µF ceramic capacitor (CS1) between PVCC and PGND and one additional ceramic
capacitor 0.1 µF (CS2) are enough. A 1 µF capacitor must be located as close as possible to
the device PVCC pin in order to avoid any extra parasitic inductance or resistance created
by a long track wire. Parasitic loop inductance, in relation with di/dt, introduces overvoltage
that decreases the global efficiency of the device and may cause, if this parasitic inductance
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