| Rl | Inverting input resistance to provide AC gain in conjunction with RF. This input is biased at the BIASCAP voltage (approximately 2.5VDC). |
| cl | AC input coupling capacitor which, in conjunction with Ri, forms a highpass filter at fc = 1/(2RiCi) . |
| RFB | Feedback resistor connected from either the half-bridge output to FDBKN1 (FDBKN2) or speaker ground to GNDKELVINl (GNDKELVIN2). The value of this depends on the supply voltage range and sets the TDA2500 gain in conjunction with Ri. It should be noted that the feedback resistor from the half-bridge output must have a power rating of greater that PDISS = VPP2/2RFB. Please see the Modulator Feedback Design paragraphs in the Application Information Section. |
| CFB | Feedback delay capacitor that both lowers the idle switching frequency and filters very high frequency noise from the feedback signal, which improves amplifier performance. The value of CFB should be offset between channel l and channel 2 so that the idle switching difference is greater than 40kHz. Please refer to the Application / Test Circuit. |
| ROFA | Potentiometer used to manually trim the DC offset on the output of the TDA2500. |
| ROFB | Resistor that limits the manual DC offset trim range and allows for more precise adjustment. |
| COF | Decoupling capacitor which low pass filters the offset trim voltage from noise and power supply fluctuations. |
| Cs | Supply decoupling for the power supply pins. For optimum performance, these components should be located close to the TDA2500 and returned to their respective ground as shown in the Application/Test Circuit. |
| Rs | Over-current sense resistor. Please refer to the section, Setting the Over-current Threshold, in the Application Information for a discussion of how to choose the value of Rs to obtain a specific current limit trip point. |
| ROCR | Over-current "trim" resistor, which, in conjunction with Rs, sets the current trip point. Please refer to the section, Setting the Over-current Threshold, in the Application Information for a discussion of how to calculate the value of ROCR. |
| CHBR | Supply decoupling for the high current Half-bridge supply pins. These components must be located as close to the output MOSFETs as possible to minimize output ringing which causes power supply overshoot. By reducing overshoot, these capacitors maximize both the TDA2500 and output MOSFET reliability. These capacitors should have good high frequency performance including low ESR and low ESL. In addition, the capacitor rating must be twice the maximum VPP voltage. |
| Qo | Output MOSFET. This is the main output switching device and to a large extent, sets the amplifier's limitations. This device must be a switching grade device with a good compromise between gate charge and on resistance while being able to withstand the full supply range. Please refer to the recommended devices in the Applications Information section. |
| Do | Output diode, which is used to minimizes output overshoots/undershoots on the output node. These devices clamp the output to low impedance node formed by the close connection of CHBR. Note the connection shown in the Application/Test Circuit. The "drain to drain" diode protects the bottom side device from excessive BVDSS due to overshoots on the output node. The "source to source" diode protects the top side device from excessive BVDSS due to undershoots on the output node. This device must be an ultra fast rectifier capable of sustaining the entire supply range (VPP-VNN) and high peak currents. |
| RG | Gate resistor, which is used to control the MOSFET rise/ fall times. This resistor serves to dampen the parasitics at the MOSFET gates, which, in turn, minimizes ringing and output overshoots. The typical power rating is l watt. |
| Cz | Zobel capacitor, which in conjunction with Rz, terminates the output filter at high frequencies. Use a high quality film capacitor capable of sustaining the ripple current caused by the switching outputs. |
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