Charge Pump Flying Capacitor and PVSS Capacitor

Decoupling Capacitors

Gain setting resistors ranges

Input-Blocking Capacitors

fc

1

2p R

C

1

2p fc

or

(3)

Supply Voltage Limiting At 4.5 V

Capacitive load

DRV601

The charge pump flying capacitor serves to transfer charge during the generation of the negative supply voltage.

The PVSS capacitor must be at least equal to the charge pump capacitor in order to allow maximum charge

transfer. Low ESR capacitors are an ideal selection, and a value of 1µF is typical. Capacitor values that are

smaller than 1µF can be used, but the maximum output voltage may be reduced and the device may not operate

to specifications.

The DRV601 is a DirectPath™ Line Driver amplifier that require adequate power supply decoupling to ensure

that the noise and total harmonic distortion (THD) are low. A good low equivalent-series-resistance (ESR)

decoupling capacitor close to the DRV601 is important for the performance of the amplifier. For filtering lower

frequency noise signals, a 10-µF or greater capacitor placed near the audio power amplifier would also help, but

it is not required in most applications because of the high PSRR of this device.

high increases the noise of the amplifier. Table 1 lists the recommended resistor values for different gain

settings.

Table 1. Recommended Resistor Values

Gain

-1 V/V

10 k

Ω

10 k

Ω

-1.5 V/V

10 k

Ω

15 k

Ω

-2 V/V

10 k

Ω

20 k

Ω

-10 V/V

4,7 k

Ω

47 k

Ω

DC input-blocking capacitors are required to be added in series with the audio signal into the input pins of the

DRV601. These capacitors block the DC portion of the audio source and allow the DRV601 inputs to be properly

biased to provide maximum performance.

Equation 3. For this calculation, the capacitance used is the input-blocking capacitor and the resistance is the

input resistor chosen from the gain table above, then the frequency and/or capacitance can be determined when

one of the two values are given.

The DRV601 have a built-in charge pump which serves to generate a negative rail for the line driver. Because

the line driver operates from a positive voltage and negative voltage supply, circuitry has been implemented to

protect the devices in the amplifier from an overvoltage condition. Once the supply is above 4.5 V, the DRV601

can shut down in an overvoltage protection mode to prevent damage to the device. The DRV601 resume normal

operation once the supply is reduced to 4.5 V or lower.

The DRV601 has the ability to drive a high capacitive load up to 330pF directly, higher capacitive loads can be

accepted by adding a series resistor of 10

Ω or larger. The figure below shows a 10kHz signal into a 470pF

capacitor using the 10R series resistor.

Copyright © 2008, Texas Instruments Incorporated

9

Product Folder Link(s): DRV601