TDA5345HT Datasheet, PDF (28/44 Pages) NXP Semiconductors – 5 V spindle & VCM driver combo

Philips Semiconductors
5 V spindle & VCM driver combo
Preliminary specification
TDA5345HT
Power on reset
The Power On Reset circuit monitors the voltage level of +5 V supply voltage (pin named VddAna1).
The PorN output (pin #25) is set HIGH when the +5 V supply voltage arise above a specified voltage threshold plus an
hysteresis. This LOW to HIGH transition is delayed by a time T_C that is determined by the external PorCap capacitor
(connected to pin #26).
This PorN output remains HIGH until +5 V supply drops below its voltage threshold. PorN output immediately becomes
LOW. A brake after retract is initiated and the digital section is reset while PorN remains LOW.
The C_PorCap capacitor is charged by a constant current I_PorCap. The voltage on PorCap pin is compared to the POR circuit
reference voltage V_PorRef. The T_C time is set then by the following equation:
T_C = C_PorCap × ^V-I--_P--^P-_o--^o-_r--^rC--^R--_a-^e-_p--^f = C_PorCap × _2--1---â‹-.-2-1---3-0--V-_–---₆- = C_PorCap × 615 ⋅ 10³
(19)
The T_C time value only depends on the external C_PorCap capacitor value.
VDD
V_hysteresis
1V
POR_N
T_c
T_c
threshold
t
t
Fig.21 Power on reset timing
The value of the +5 V supply threshold voltage can be adjusted by adding an external resistor divider on the Por5Adj(28)
. Internally, pin is designed as it is described in figure 20.
Fig.22 Por5vAdj pin
(24)
VddAna1
Por5Adj
(28)
R_H5
R_L5
to the POR circuit
(32)
GndAna2
It is advised to connect external capacitors on pins Por5Adj to filter the power supplies noise. See figure 21.
1999 June 10
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