DRV601_08 Datasheet, PDF (9/16 Pages) Texas Instruments – DIRECTPATH™ STEREO LINE DRIVER, ADJUSTABLE GAIN

DRV601
www.ti.com ................................................................................................................................................ SLOS553A – JANUARY 2008 – REVISED AUGUST 2008
Charge Pump Flying Capacitor and PVSS Capacitor
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.
Decoupling Capacitors
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)
ceramic capacitor, typically 2.2µF, placed as close as possible to the device V_DD lead works best. Placing this
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.
Gain setting resistors ranges
The gain setting resistors, R_in and R_fb, must be chosen so that noise, stability and input capacitor size of the
DRV601 is kept within acceptable limits. Voltage gain is defined as R_fb divided by R_in.
Selecting values that are too low demands a large input ac-coupling capacitor, C_IN . Selecting values that are too
high increases the noise of the amplifier. Table 1 lists the recommended resistor values for different gain
settings.
Gain
-1 V/V
-1.5 V/V
-2 V/V
-10 V/V
Table 1. Recommended Resistor Values
Input Resistor Value, R_in
10 kΩ
10 kΩ
10 kΩ
4,7 kΩ
Feedback Resistor Value, R_fb
10 kΩ
15 kΩ
20 kΩ
47 kΩ
Input-Blocking Capacitors
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.
These capacitors form a high-pass filter with the input resistor, R_in. The cutoff frequency is calculated using
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.
fc_IN
+
2p
1
R_IN
C_IN
or
C_IN
+
2p
1
fc_IN
R_IN
(3)
Supply Voltage Limiting At 4.5 V
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.
Capacitive load
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 10Ω or larger. The figure below shows a 10kHz signal into a 470pF
capacitor using the 10R series resistor.
Copyright © 2008, Texas Instruments Incorporated
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Product Folder Link(s): DRV601