TC2001 datasheet(23/34 Pages) TRIPATH

23 / 34 page

Tr i p ath Technol ogy, I n c. - Techni cal In fo rma t io n

TK2150 – Rev. 1.0/12.02

VPPSENSE (pin 19) performs the over and undervoltage sensing for the positive supply, VPP.

VNNSENSE (pin 17) performs the same function for the negative rail, VNN. When the current

through RVPPSENSE (or RVNNSENSE) goes below or above the values shown in the Electrical

Characteristics section (caused by changing the power supply voltage), the TK2150 will be

muted. VPPSENSE is internally biased at 2.5V and VNNSENSE is biased at 1.25V.

Once the supply comes back into the supply voltage operating range (as defined by the supply

sense resistors), the TK2150 will automatically be unmuted and will begin to amplify. There is a

hysteresis range on both the VPPSENSE and VNNSENSE pins. If the amplifier is powered up in

the hysteresis band the TK2150 will be muted. Thus, the usable supply range is the difference

between the over-voltage turn-off and under-voltage turn-off for both the VPP and VNN supplies.

It should be noted that there is a timer of approximately 200mS with respect to the over and

under voltage sensing circuit. Thus, the supply voltage must be outside of the user defined

supply range for greater than 200mS for the TK2150 to be muted.

Figure 5 shows the proper connection for the Over / Under voltage sense circuit for both the

VPPSENSE and VNNSENSE pins.

VPP1

VNN

VNN1

VPP1

VNN2

VPPSENSE

VNNSENSE

VPP

TC2001

Figure 5: Over / Under voltage sense circuit

The equation for calculating RVPP1 is as follows:

VPPSENSE

VPP1

VPP

Set

VPP1

VPP2

The equation for calculating RVNNSENSE is as follows:

VNNSENSE

VNN1

VNN

Set

VNN1

VNN2

IVPPSENSE or IVNNSENSE can be any of the currents shown in the Electrical Characteristics

table for VPPSENSE and VNNSENSE, respectively.

The two resistors, RVPP2 and RVNN2 compensate for the internal bias points. Thus, RVPP1 and

RVNN1 can be used for the direct calculation of the actual VPP and VNN trip voltages without

considering the effect of RVPP2 and RVNN2.

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