Functions, pins and components description TDA7570
12/17
4 Functions, pins and components description
4.1 Components with critical placement and type:
● Ci-L1, Ci-L2, Ci-R1, Ci-R2 must be placed as near as possible to the sources of the
respective power MOS. If 2 power MOS in parallel are needed, can be useful to place a
couple of capacitors for each couple of power MOS. These capacitors are needed to
absorb the high di/dt current present during the Pchannel/Nchannel and
Nchannel/Pchannel transition that can cause high peak voltages on the power supply
wiring connection due to their parasitic inductance.
● The capacitors placed between +Vs to GND and to -Vs are distributed along the power
lines. With P.C. board with very short connections, some of these capacitors can be
avoided (Cvs-1, Cvs-2, Cd3, Cd4, Cd5, Cd6).
● The current sensing resistors Rsens-N-L, Rsens-P-L, Rsens-P-R and Rsens-N-R must
be not inductive components, as example, made by a costant an wire.
4.2 Input capacitors
● The value of the input capacitors (Cin-L+, Cin-L-, Cin-R+, Cin-R- depends on the
desired -3dB high pass cutoff frequency, following the formula:
4.3 Short circuit protection current calculation
Figure 4. Short circuit protection current diagram (example for the N-channel)
if Rp2 is not used
F3dB
1
6.28 10000 C
in
----------------------------------------------=
Cfil (typ 2.2nF)
to -Vs
Rsens
(not inductive resistor)
Typ. Values = 10 – 30 mOhm
Rfil (typ. 100 Ohm)
Rp1 (typ=4.7kOhm)
Rp2
Vfil = Ispx1 x Rfil = 20mV Typ
SPx1 pin
SPx2 pin
TDA7570
Vp=100mV Typ
comparator
Imos
I
lim
1
Rsens
------------------
Vpx Rp1 Rp2+
Rp2
------------------------------------------------- - Vfil+
=
I
lim
1
Rsens
------------------
Vpx Vfil+=
