BH7881EFV-E2 Datasheet BH7881EFV-E2 | P4-P6

Technical Note

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BH7881EFV

●Description of operations

1. LINE Amplifier

1) The voltage gain of the LINE amplifier is calculated by the following equations:

GAIN = 20×LOG(68k/R4 +1k)) [dB]

GAIN = 20×LOG(68k/R9 +1k)) [dB]

R4 and R9 are resistances connected to PIN4 and PIN9

2) In order to make it operable with mixing input, the LINE amplifier can be realized by connecting multiple resistors to

PIN4 and PIN9. Since the input pin is also the feedback of an inverting differential amplifier, each individual signal is

simply added.

3) To configure LPF and remove unnecessary frequency components, the LINE amplifier can be realized by connecting

capacitors between PIN3 and PIN4, and between PIN9 and PIN10. The LPF cut-off frequency at that time is calculated

by the following equation:

fc = 1/(2×π×C×68k) [Hz]

2. SP Amplifier (HP Amplifier)

1) The voltage gain of the SP amplifier for Non-Boost is about 12 [dB] (SE: Single end).

2) The voltage gain of the SP amplifier for Bass-Boost is calculated by the following equations:

GAIN = 20×LOG((40k+R22-23)/10k) [dB]

Where R22-23 is the resistance connected between PIN22 and PIN23.

GAIN = 20×LOG((40k+R14-15)/10k) [dB] Where R14-15 is the resistance connected between PIN14 and PIN15.

3) The cut-off frequency for Bass-Boost is calculated by the following equations:

fc = 1/(2×π×C22-23×R22-23) [Hz]

Where RC22-23 is connected between PIN22 and PIN23.

fc = 1/(2×π×C14-15×R14-15) [Hz] Where RC14-15 is connected between PIN14 and PIN15.

4) Apply power to RCHVCC (PIN13), for MONO only.

3. Regulator

1) The REG output voltage is calculated by the following equation, and numeric values are shown below:

V = 1.15 [V]×(1+R(VLEV)/R(VREF)) [V]

REG setting voltage 3.0 3.3 3.6 4.0 4.6 V

Supply voltage(VCC) 3.3 3.6 4.0 5.0 5.0 V

R(VLEV) 30k 30k 30k 30k 30k Ω

R(VREF) 18k 16k 14k 12k 10k Ω

Use 1% resistors to eliminate errors in actual output voltages.

2) The REG maximum output current is determined by the external Tr capability (hFE) of the IC. If more current is

necessary, select one ICMAX with large hFE. Drive output current to the base is about 5 mA.

3) When using the regulator, connect REG output to PIN6. The LINE amplifier, BIAS, and other sections essential to tone

quality, are driven by the REG voltage. Clear sound output is obtained even if a digital power supply is the VCC.

4) When using the regulator for an application, other than this IC, and driving the IC by VCC only, apply VCC at PIN6.

5) When not using the regulator, it is set to OFF mode by connecting PIN 19 to OPEN and PIN18 to OPEN. Apply VCC at

PIN6.

6) Do not set a VCC applied voltage that is smaller than the set voltage of the regulator. Since the REG output transistor

operates in a saturation region, an abnormal circuit current occurs.

7) For the REG output transistor, Rohm transistors 2SA1900 and 2SA933 are recommended.

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BH7881EFV

4. Short circuit detection

1) Overview of SP amplifier VCC/GND short circuit detection.

If the output pin of the SP amplifier is short circuited to VCC or GND, the detection function operates to suspend the

output stage of the SP amplifier.

If the SP output pin is short circuited to REG output, the detection function does not operate. It is configured so that it

resets automatically if the short circuit is canceled. Moreover, although a short circuit is detected from the DC voltage

of the output pin, and there is a short delay distinguishing it from maximum output amplitude, malfunction may occur

due to factors such as power supply voltage and load. In this case, connect “PIN7” to GND. The short circuit function

is set to the OFF mode.

2) SP amplifier VCC/GND short circuit detection cautions

When the output pin of the SP amplifier is short circuited with VCC or GND, excessive current flows in the IC and stress

is applied to the chip. Accordingly, if it is shorted a number of times, the IC gradually deteriorates and is finally

destroyed. The short circuit detection function does not guarantee operation after numerous shorts.

3) Regulator short circuit detection

If the output pin of the regulator is short circuited to GND, the detection function operates to suspend the output stage

of the regulator. If the output pin of the regulator is short circuited to VCC, an abnormal current does not occur in any

circuit. After the short circuit, the regulator resets automatically, due to the pull-up resistance (for example, 2.2 k)

connected to PIN1, as shown in the full option example of the sample application circuit.

(Example: 3.9 kΩ is the resistance load for lowering the output impedance of the regulator when it is no load.)

5. Pop noise

1) The following table shows the sequence for eliminating the pop noise that occurs from turning the power supply

ON or OFF, or turning control pins ON or OFF.

Order VCC ACT/SPND SP/HP Conditions

1 OFF SUSPEND HP Power Supply ON

2 ON SUSPEND HP Turning on in the suspend

3 ON ACTIVE HP SP MUTE～countermeasure

4 ON ACTIVE SP+HP MUTE cancellation～operation

5 ON ACTIVE SP+HP Operation

6 ON ACTIVE HP SP MUTE～counter measure

7 ON SUSPEND HP Turning off in the suspend

8 OFF SUSPEND HP Power Supply OFF

2) In speaker MUTE state, pop noise does not occur even when starting or changing modes. It is recommended to use

speaker MUTE (headphone) mode during conditions where pop noise can occur.

3 ) Any changes of the components values in the sample application circuit can the effect the pop noise cut-off function.

6. Bypass and bias capacitor

1) Although this IC is designed so that bypass capacitors are not needed, when bypass capacitors are in fact necessary,

place them close to the VCC~GND pins.

2) Similarly, place a bias capacitor close to the GND pin.

7. Capacitive load drive

1) Do not connect a capacitive load to the SP amplifier, HP amplifier, or IC pin. There is a possibility of oscillation.

2) Adding RC to the HP amplifier output, as in the sample application circuit, makes the output noise, voltage, and

distortion sensitive to oscillation.

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BH7881EFV

8. Pop noise at start/end when switching ACTV/SPND

Pop noise can be suppressed by mode transition due to software as in “Pop noise” above, or by hardware as shown below.

This is realized (in SP mode) by forcibly setting HP mode temporarily, using the CR differential circuit.

Fig.2

9. Power package

1) In order to expand the power dissipation of the package, make the GND pattern, directly below the IC, as wide as

possible and solder the GND pattern to the back of the IC.

2) Power dissipation of the package varies greatly depending on factors such as the number of layers, area, film thickness,

and material quality of the board used.

10. Other

Beween voltages of VCC=1.4～1.6 V, momentary oscillation sometimes is observed at the SPOUT pin. Nevertheless, this

occurrence is not reproduced on a momentary rise or fall of VCC. When slowly raising VCC pay attention to transient

voltage. In order to avoid such occurrences, a sample circuit is illustrated below:

Fig.3

P1-P3 P4-P6 P7-P9 P10-P10

BH7881EFV-E2

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