BD5446EFV_11 Datasheet, PDF (29/32 Pages) Rohm – Class-D Speaker Amplifier for Digital Input

BD5446EFV
Technical Note
●Notes for use
1 ) Absolute maximum ratings
Use of the IC in excess of absolute maximum ratings such as the applied voltage or operating temperature range may result in IC
damage. Assumptions should not be made regarding the state of the IC (short mode or open mode) when such damage is suffered. A
physical safety measure such as a fuse should be implemented when use of the IC in a special mode where the absolute maximum
ratings may be exceeded is anticipated.
2 ) Power supply lines
As return of current regenerated by back EMF of output coil happens, take steps such as putting capacitor between power supply and
GND as a electric pathway for the regenerated current. Be sure that there is no problem with each property such as emptied capacity at
lower temperature regarding electrolytic capacitor to decide capacity value. If the connected power supply does not have sufficient
current absorption capacity, regenerative current will cause the voltage on the power supply line to rise, which combined with the product
and its peripheral circuitry may exceed the absolute maximum ratings. It is recommended to implement a physical safety measure such
as the insertion of a voltage clamp diode between the power supply and GND pins.
3 ) GND potential(Pin 6, 36, 37, 45, 46).
Any state must become the lowest voltage about GND terminal and VSS terminal.
4 ) Input terminal
The parasitic elements are formed in the IC because of the voltage relation. The parasitic element operating causes the wrong operation
and destruction. Therefore, please be careful so as not to operate the parasitic elements by impressing to input terminals lower voltage
than GND and VSS. Please do not apply the voltage to the input terminal when the power-supply voltage is not impressed.
5 ) Setting of heat
Use a thermal design that allows for a sufficient margin in light of the power dissipation (Pd) in actual operating conditions. This IC
exposes its frame of the backside of package. Note that this part is assumed to use after providing heat dissipation treatment to improve
heat dissipation efficiency. Try to occupy as wide as possible with heat dissipation pattern not only on the board surface but also the
backside.
Class D speaker amplifier is high efficiency and low heat generation by comparison with conventional Analog power amplifier. However,
In case it is operated continuously by maximum output power, Power dissipation (Pdiss) may exceed package dissipation. Please
consider about heat design that Power dissipation (Pdiss) does not exceed Package dissipation (Pd) in average power (Poav). (Tjmax :
Maximum junction temperature=150℃, Ta : Peripheral temperature[℃], θja : Thermal resistance of package[℃/W], Poav : Average
power[W], η : Efficiency)
Package dissipation : Pd(W)=(Tjmax - Ta)/θja
Power dissipation : Pdiss(W)= Poav ×(1/η- 1)
6 ) Actions in strong magnetic field
Use caution when using the IC in the presence of a strong magnetic field as doing so may cause the IC to malfunction.
7 ) Thermal shutdown circuit
This product is provided with a built-in thermal shutdown circuit. When the thermal shutdown circuit operates, the output transistors are
placed under open status. The thermal shutdown circuit is primarily intended to shut down the IC avoiding thermal runaway under
abnormal conditions with a chip temperature exceeding Tjmax = 150℃.
8 ) Shorts between pins and misinstallation
When mounting the IC on a board, pay adequate attention to orientation and placement discrepancies of the IC. If it is misinstalled and
the power is turned on, the IC may be damaged. It also may be damaged if it is shorted by a foreign substance coming between pins of
the IC or between a pin and a power supply or a pin and a GND.
9 ) Power supply on/off (Pin 25, 28, 29, 53, 54)
In case power supply is started up, RESETX(Pin 12), MUTEX(Pin 13) and PDX (Pin 14) always should be set Low. And in case power
supply is shut down, it should be set Low likewise. Then it is possible to eliminate pop noise when power supply is turned on/off. And also,
all power supply terminals should start up and shut down together.
10 ) ERROR terminal(Pin 24)
A error flag is outputted when Output short protection and DC voltage protection in the speaker are operated. These flags are the
function which the condition of this product is shown in.
11 ) N.C. terminal(Pin 26, 30, 34, 35, 41, 47, 48, 52)
N.C. terminal (Non Connection Pin) does not connect to the inside circuit. Therefore, possible to use open.
12 ) TEST terminal(Pin 19, 20)
TEST terminal connects with ground to prevent the malfunction by external noise.
13 ) Precautions for Spealer-setting
If the impedance characteristics of the speakers at high-frequency range while increase rapidly, the IC might not have stable-operation
in the resonance frequency range of the LC-filter. Therefore, consider adding damping-circuit, etc., depending on the impedance of
the speaker.
14) Notes about the phase of SYS_CLK (Pin7) and BCLK (Pin8)
If the rising edge of SYS_CLK (Pin7) and BCLK (Pin8) becomes simultaneous, noise or sound shutdown may occur.
Please cope with it, when the rising edge of CYC_CLK and BCLK becomes simultaneous. (Example: Insert RC filter in BCLK)
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2011.06 - Rev.C