參數(shù)資料
型號: TPA0252PWPR
廠商: TEXAS INSTRUMENTS INC
元件分類: 音頻控制
英文描述: 2 CHANNEL(S), VOLUME CONTROL CIRCUIT, PDSO24
封裝: GREEN, PLASTIC, HTSSOP-24
文件頁數(shù): 9/34頁
文件大小: 851K
代理商: TPA0252PWPR
www.ti.com
CLK
VOLUME
4 cycles per step
UP
V
AUX
V
DD
System
V
AUX
CVAUX
VAUX
9
INPUT RESISTANCE
TPA0252
SLOS288B – JUNE 2000 – REVISED SEPTEMBER 2004
Figure 33. External Clock (4 Cycles Per Volume Change)
VAUX is used to keep power to the volume control memory. As long as the voltage at the VAUX pin is greater
than 3 V, the device remembers what volume setting it was in, even when shut-down or powered down. The
amplifier then returns to that volume setting after being powered up. If VAUX is pulled low, the device resets to a
volume setting of -10 dB in BTL and -16 dB in SE mode. If VAUX is pulled below ground, the device could be
damaged. Even if VAUX is connected to just one voltage, it must be connected through a diode so VAUX is not
pulled below ground. The recommended circuit to keep VAUX high when power down is shown below.
To ensure proper operation, the VAUX voltage must not drop below 1.5 V. If the voltage falls below 1.5 V, the
stability of the TPA0252 could be compromised. However, this does not damage the device; normal functionality
resumes once the VAUX voltage is at or above 1.5 V.
Figure 34. Recommended System VAUX Circuit
The diodes in Figure 34 need to have a low threshold voltage and low leakage current. This circuit allows VAUX
to remain high even when VDD and system VAUX are removed. The formula for calculating how long the volume is
remembered if VDD and system VAUX is removed or pulled low is shown below. The diode used in the example
has a forward voltage, VF of 0.7 V and 25 nA of leakage current, IR.
tdecay = CVAUX× ((VDD or system VAUX) - VF - VAUXmin) / (2 × IR + IDD(VAUX))
tdecay = 0.47 F × (5V - 0.7 V - 3V)/(25 nA × 2 + 0.7 nA)
tdecay = 12 seconds
The gain is set by varying the input resistance of the amplifier, which can range from its smallest value to over
six times that value. As a result, if a single capacitor is used in the input high pass filter, the –3 dB or cut-off
frequency also changes by over six times. Connecting an additional resistor from the input pin of the amplifier to
ground, as shown in Figure 35, reduces the cutoff-frequency variation.
17
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