TDA5345HT Datasheet, PDF (26/44 Pages) NXP Semiconductors – 5 V spindle & VCM driver combo

Philips Semiconductors
5 V spindle & VCM driver combo
Shock Sensor
R_HPF
C_{sensor (55)} ^Cgain _ShockAmpOut
-
ShockInput ₁
+
+
(54) ²
-
Amplifier x16.3
(50)
ShockRef
2V
Preliminary specification
TDA5345HT
Amplifier x20
Window
comparator
+
3
-
(53)
(ext.)
ShockFiltOut
ShockCompOut
R
(51)
380kΩ _{C 4}
(52)
20kΩ
ShockCom
C_com
programmable
threshold
Fig.18 Shock sensor control circuitry
The first amplifier gain is given by : G = C_gain/C_sensor. It has to be set so that the sensor voltage sensitivity becomes
220 µV/G on the 1 st stage output.
The 2^nd amplifier stage gain is internally set to 16.3. The 3^rd amplifier stage gain is internally set to 20. The external
capacitor C_com and R_HPF have to be chosen so that : C_comx20 kΩ = C_gainxR_HPF. This time constant makes the input high
pass filter pole. The internal RC low pass filter pole is 8 kHz typical. The window of the comparator input (ShockCompInP)
is programmable through the serial interface. The values are given in the following table:
Table 16 Window comparator threshold versus ShockThresh[1:0] (bits [9,8] in register #4):
SHOCKTHRESH[1:0]
000
001
010
011
100
101
110
111
WINDOW
74 mV
148 mV
222 mV
296 mV
370 mV
444 mV
518 mV
592 mV
2ND STAGE INPUT
SENSITIVITY
227 µV
454 µV
681 µV
908 µV
1.135 mV
1.362 mV
1.589 mV
1.816 mV
Temperature monitor:
The TDA5345HT includes an analog circuitry that monitors the junction temperature.
Figure 25 shows its diagram:
1999 June 10
26