NXP Semiconductors TDA8944J Specification Sheet

Contents

NXP Semiconductors TDA8944J Specification Sheet Manual pdf 6 page image

NXP Semiconductors TDA8944J2 x 7 W stereo BTL audio amplifierProduct specification Rev. 02 — 14 February 2000 6 of 229397 750 06861 © NXP B.V. 2010. All rights reserved.Mute — In this mode the amplifier is DC-biased but not operational (no audio output);the DC level of the input and output pins remain on half the supply voltage. Thisallows the input coupling and Supply Voltage Ripple Rejection (SVRR) capacitors tobe charged to avoid pop-noise. The device is in mute mode when3 V < V MODE < (V CC − 1.5 V).Operating — In this mode the amplifier is operating normally. The operating mode isactivated at V MODE < 0.5 V.8.3.1 Switch-on and switch-offTo avoid audible plops during supply voltage switch-on or switch-off, the device is setto standby mode before the supply voltage is applied (switch-on) or removed(switch-off).The switch-on and switch-off time can be influenced by an RC-circuit on the MODEpin. Rapid on/off switching of the device or the MODE pin may cause ‘click- andpop-noise’. This can be prevented by proper timing of the RC-circuit on the MODEpin.8.4 Supply Voltage Ripple Rejection (SVRR)The SVRR is measured with an electrolytic capacitor of 10 μF on pin SVR at abandwidth of 10 Hz to 80 kHz. Figure 13 on page 11 illustrates the SVRR as functionof the frequency. A larger capacitor value on the SVR pin improves the ripplerejection behaviour at the lower frequencies.8.5 Built-in protection circuitsThe TDA8944J contains two types of protection circuits, i.e. short-circuit and thermalshutdown.8.5.1 Short-circuit protectionShort-circuit to ground or supply line — This is detected by a so-called ‘missingcurrent’ detection circuit which measures the current in the positive supply line andthe current in the ground line. A difference between both currents larger than 0.4 A,switches the power stage to standby mode (high impedance).Short-circuit across the load — This is detected by an absolute-currentmeasurement. An absolute-current larger than 2 A, switches the power stage tostandby mode (high impedance).8.5.2 Thermal shutdown protectionThe junction temperature is measured by a temperature sensor; at a junctiontemperature of approximately 150 °C this detection circuit switches the power stageto standby mode (high impedance).