TDA8358J Full bridge vertical deflection output circuit in ... - Laro

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Philips SemiconductorsFull bridge vertical deflection output circuitin LVDMOS with east-west amplifierProduct specificationTDA8358JPINNINGSYMBOL PIN DESCRIPTIONINA 1 positive vertical inputINB 2 negative vertical inputV P 3 supply voltageOUTB 4 vertical output voltage BINEW 5 east-west input voltageVGND 6 vertical groundEWGND 7 east-west groundOUTEW 8 east-west output voltageV FB 9 flyback supply voltageOUTA 10 vertical output voltage AGUARD 11 guard output voltageFEEDB 12 input measuring resistorCOMP 13 input compensation currenthandbook, halfpageINAINBV POUTBINEWVGNDEWGNDOUTEWV FBOUTAGUARDFEEDBCOMP12345678910111213TDA8358JMGL867The die has been glued to the metal block of the package. If the metalblock is not insulated from the heatsink, the heatsink shall only beconnected directly to pin VGND.FUNCTIONAL DESCRIPTIONVertical output stageThe vertical driver circuit has a bridge configuration. Thedeflection coil is connected between the complimentarydriven output amplifiers. The differential input circuit isvoltage driven. The input circuit is specially designed fordirect connection to driver circuits delivering a differentialsignal but it is also suitable for single-ended applications.For processors with output currents, the currents areconverted to voltages by the conversion resistorsR CV1 and R CV2 (see Fig.3) connected to pins INAand INB. The differential input voltage is compared withthe voltage across the measuring resistor R M , thusproviding feedback information. The voltage across R M isproportional with the output current. The relationshipbetween the differential input voltage and the outputcurrent is defined by:V i(dif)(p-p) = I o(p-p) × R M ; V i(dif)(p-p) = V INA − V INBThe output current should not exceed 3.2 A (p-p) and isdetermined by the value of R M and R CV . The allowableinput voltage range is 100 mV to 1.6 V for each input. Theformula given does not include internal bondwireresistances. Depending on the value of R M and the internalbondwire resistance (typical value 50 mΩ) the actual valueof the current in the deflection coil will be about 5% lowerthan calculated.Flyback supplyThe flyback voltage is determined by the flyback supplyvoltage V FB . The principle of two supply voltages (class G)allows to use an optimum supply voltage V P for scan andan optimum flyback supply voltage V FB for flyback, thusvery high efficiency is achieved. The available flybackoutput voltage across the coil is almost equal to V FB , dueto the absence of a coupling capacitor which is notrequired in a bridge configuration. The very short rise andfall times of the flyback switch are determined mainly bythe slew rate value of more than 300 V/µs.ProtectionThe output circuit contains protection circuits for:• Too high die temperature• Overvoltage of output A.Fig.2 Pin configuration.2002 Sep 25 4
Philips SemiconductorsFull bridge vertical deflection output circuitin LVDMOS with east-west amplifierProduct specificationTDA8358JGuard circuitA guard circuit with output pin GUARD is provided.The guard circuit generates a HIGH-level during theflyback period. The guard circuit is also activated for oneof the following conditions:• During thermal protection (T j ≈ 170 °C)• During an open-loop condition.The guard signal can be used for blanking the picture tubeand signalling fault conditions. The verticalsynchronization pulses of the guard signal can be used byan On Screen Display (OSD) microcontroller.Damping resistor compensationHF loop stability is achieved by connecting a dampingresistor R D1 (see Fig.4) across the deflection coil. Thecurrent values in R D1 during scan and flyback aresignificantly different. Both the resistor current and thedeflection coil current flow into measuring resistor R M ,resulting in a too low deflection coil current at the start ofthe scan.The difference in the damping resistor current valuesduring scan and flyback have to be externallycompensated in order to achieve a short settling time.For that purpose a compensation resistor R CMP isconnected between pins OUTA and COMP. The value ofR CMP is calculated by:( VR FB – V loss( FB)– V P ) × R D1 ×( R S + 300)CMP = -------------------------------------------------------------------------------------------------------------( V FB– V loss( FB)– I coil( peak)× R coil) × R Mwhere:• R coil is the coil resistance• V loss(FB) is the voltage loss between pins V FB and OUTAat flyback.East-west amplifierThe east-west amplifier is current driven. The output canonly sink currents of the diode modulator circuit.A feedback resistor (see Fig.4) has to be connectedbetween the input and output of the inverting east-westamplifier in order to convert the east-west correction inputcurrent into an output voltage. The output voltage of theeast-west circuit at pin OUTEW is given by:V OUTEW ≈ I INEW × R EWF +V INEWThe maximum output voltage is V o(max) = 68 V, while themaximum output current of the circuit is I o(max) = 750 mA.2002 Sep 25 5
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