1999 June 10

28

Philips Semiconductors

Preliminary specification

5 V spindle & VCM driver combo

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

(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.

(19)

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.

It is advised to connect external capacitors on pins Por5Adj to filter the power supplies noise. See figure 21.

T

C

C

PorCap

V

PorRef

I

PorCap

-------------------

×

C

PorCap

1.23V

2 10

6

–

⋅

-------------------

×

C

PorCap

615 10

3

⋅

×

=

=

=

Fig.21 Power on reset timing

VDD

threshold

t

t

POR_N

1 V

VddAna1

Por5Adj

to the POR circuit

Fig.22 Por5vAdj pin

GndAna2

(32)

(24)

(28)