TB2902HQ Просмотр технического описания (PDF) - Toshiba
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TB2902HQ Datasheet PDF : 38 Pages
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TB2902HQ
Caution and Application Information (description is made referring only on the single
channel.)
1. Voltage Gain Adjustment
This IC has no NF (negative feedback) Pins. Therefore, the voltage gain can not be adjusted (except by
software). However, this feature makes possible space and cost saving.
Input
Amp. 1
Amp. 2A
Amp. 2B
Figure 1 Block Diagram
The amplifier gain, GV = 26dB, is calculated using the expression below:
The voltage gain of amp.1: GV1 = 0dB
The voltage gain of amp.2A, B: GV2 = 20dB
The voltage gain of BTL connection: GV (BTL) = 6dB
Therefore, the total voltage gain is decided by expression below.
GV = GV1 + GV2 + GV (BTL) = 0 + 20 + 6 = 26dB
In the case when GV = 12dB selected via I2C, GV1 changed from 0dB to −14dB so that the output
dynamic range is reduced as the output of Amp.1 is attenuated.
2. Muting Time Constant and Pop Noise Suppression when VCC Rapidly Falls (pin 16)
The capacitor C4 at pin 16 is for muting time
constant to suppress the pop noise. The larger
value capacitor is used, the lower pop noise
becomes but the longer the muting time from the
mute ON command sent to muting an output
16
sound actually. The charge period, which makes
To mute circuit
the delay of muting after "Mute On" command is
written, is MIN=30msec, MAX=180msec in case
of C4 (Pin 16) = 1 uF, Vcc=9 to 18V and Tj = -40
to 150 degrees condition.
From low voltage
muting circuit
As the VCC is rapidly falling, the IC internal low
voltage muting operates to eliminate the large
pop noise basically.
If the effect of the internal low voltage muting
is not enough in such a case, make this pin 16 set
at low: 5 V and less by external circuit for more
Figure 2 Pin 16 Muting Circuit
effective to suppress the pop noise.
In this case, this pin 16 has to be released from setting at low before going back to play mode.
Additionally, the initial state after turning the amplifier “ON” or after turning stand by “off” by I2C Bus
is muted, so that it is necessary to send a “mute off” command to change from this condition to play mode.
Caution on the use of the muting function
The audio muting function is enabled when pin 16 is not set Low. While the time constant of the muting
function is determined by the value of C4, the designer should take into account the possible generation of
pop noise during switching operations. The pop noise which is generated when the power or muting
function is turned ON/OFF will vary according to the time constant set by capacitor C4 value.
In the case when C4 value is large and the time constant is long, pop noise will be suppressed during the
time interval when the voltage on pin 16 is falling.
However, the pop noise may become apparent as a “peaky” sound if the mute ON or OFF command is
sent from µController while the voltage at pin 16 is rising.
3
2004-08-18
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