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| IC for Switched-Mode Power Supplies (SMPS) TDA 4714 C TDA 4716 C Bipolar IC Features q q q q q q q q q q Push-pull outputs (open collector) Double pulse suppression Dynamic current limitation Overvoltage protection IC undervoltage protection Reference voltage source Reference overload protection Soft start Feed-forward control Operational amplifier (TDA 4716 C) P-DIP-14-1 P-DIP-16-1 Type s TDA 4714 C s TDA 4716 C s Not for new design Ordering Code Q67000-A8312 Q67000-A8313 Package P-DIP-14-1 P-DIP-16-1 These versatile SMPS ICs comprise digital and analog functions which are required to design high-quality flyback, single-ended, and push-pull converters in normal, halfbridge and full-bridge configurations. The components can also be used in single-ended voltage multipliers and speed-controlled motors. Malfunctions in electrical operation are recognized by the integrated op amps which activate protective functions. Semiconductor Group 1 09.94 TDA 4714 C TDA 4716 C Pin Configurations (top view) TDA 4714 C TDA 4716 C Semiconductor Group 2 TDA 4714 C TDA 4716 C Pin Definitions and Functions (TDA 4714 C) Pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Symbol Function Reference voltage Supply voltage Output Q2 Output Q1 Soft start VCO RT VCO CT Ramp generator RR Ramp generator CR Input comparator Input overvoltage Dynamic current limitation (-) Dynamic current limitation (+) Ground Pin Definitions and Functions (TDA 4716 C) Pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Symbol Function Reference voltage VREF Supply voltage VS Output Q2 Output Q1 Soft start VCO RT VCO CT Ramp generator RR Ramp generator CR Operational amplifier output Operational amplifier input (-) Operational amplifier input (+) Input overvoltage Dynamic current limitation (-) Dynamic current limitation (+) Ground VREF + VS Q2 Q1 VREF VS Q2 Q1 Csoft start RT CT RR CR I COMP I OV - IDYN + IDYN GND Csoft start RT CT RR CR Q op amp - I op amp + I op amp I OV - IDYN + IDYN GND Semiconductor Group 3 TDA 4714 C TDA 4716 C Circuit Description The following is a description of the individual functional units and their interaction. Voltage Controlled Oscillator (VCO) The VCO generates a sawtooth voltage. The duration of the falling edge is determined by the value of CT. The duration of the rising edge of the waveform and, therefore, approximately the frequency, is determined by the value of RT. During the fall time, the VCO provides a trigger signal for the ramp generator, as well as an L signal for a number of IC parts to be controlled. Ramp Generator The ramp generator is triggered by the VCO and oscillates at the same frequency. The duration of the falling edge of the ramp generator waveform is to be shorter than the fall time of the VCO. To control the pulse width at the output, the voltage of the rising edge of the ramp generator signal is compared with a DC voltage at comparator K2. The slope of the rising edge of the ramp generator signal is controlled by the current through RR. This offers the possibility of an additional, superimposed control of the output duty cycle. This additional control capability, called "feed-forward control", is utilized to compensate for known interference such as ripple on the input voltage. Push-Pull Flipflop The push-pull flipflop is switched by the falling edge of the VCO. This ensures that only one output of the two push-pull outputs is enabled at a time. Comparator K2 The two plus inputs of the comparator are switched such that the lower plus level is always compared with the level of the minus input. As soon as the voltage of the rising sawtooth edge exceeds the lower of the two plus levels, both outputs are disabled via the pulse turn-OFF flipflop. The period during which the respective, active output is low can be infinitely varied. As the frequency remains constant, this process corresponds to a change in duty cycle. Operational Amplifier K1 (TDA 4716 C) The op amp K1 is a high-quality amplifier. Fluctuations in the output voltage of the power supply are amplified by K1 and applied to the free positive input of comparator K2. Variations in output voltage are, in this way, converted to a corresponding change in output duty cycle. K1 has a common-mode input voltage range between 0 V and + 5 V. Semiconductor Group 4 TDA 4714 C TDA 4716 C Pulse Turn-OFF Flipflop The pulse turn-OFF flipflop enables the outputs at the start of each half cycle. If an error signal from comparator K7 or a turn-off signal from K2 is present, the outputs will immediately be switched off. Comparator K3 Comparator K3 limits the voltage of capacitance Csoft start (and also at K2!) to a maximum of + 5 V. The voltage at the ramp generator output may, however, rise to 5.5 V. With a corresponding slope of the rising ramp generator edge, the duty cycle can be limited to a desired maximum value. Comparator K4 The comparator has its switching threshold at 1.5 V and sets the error flipflop with its output if the voltage at capacitance Csoft start is below 1.5 V. However, the error flipflop accepts the set signal only if no reset pulse (error) is applied. In this way the outputs cannot be turned on again as long as an error signal is present. Soft Start The lower one of the two voltages at the plus inputs of K2 is a measure for the duty cycle at the output. At the instant of turning on the component, the voltage at capacitor Csoft start equals 0 V. As long as no error is present, this capacitor is charged with a current of 6 A at the maximum value of 5 V. In case of an error, Csoft start is discharged with a current of 2 A. A set signal is pending at the error flipflop below a charge of 1.5 V and the outputs are enabled if no reset signal is pending simultaneously. As the minimum ramp generator voltage, however, is 1.8 V, the duty cycle at the outputs is actually increased slowly and continuously not before the voltage at Csoft start exceeds 1.8 V. Error Flipflop Error signals, which are led to input R of the error flipflop cause an immediate disabling of the outputs, and after the error has been eliminated, the component to switch on again by the soft start. Comparator K5, K8, VREF Overcurrent Load These are error detectors which cause immediate disabling of the outputs via the error flipflop when an error occurs. After elimination of the error, the component switches on again by the soft start. Semiconductor Group 5 TDA 4714 C TDA 4716 C Comparator K7 K7 serves to recognize overcurrents. This is the reason why both inputs of the operational amplifier have been brought out. Turning on is resumed after error recovery at the beginning of the next half period but without using the soft start. K7 has a commonmode input voltage range between 0 V and + 4 V. The delay time between occurrence of an error and disabling of the outputs is only 250 ns. Outputs Both outputs are transistors with open collectors and operate in a push-pull arrangement. They are actively low. The time in which only one of the two outputs is conductive can be varied infinitely. The length of the falling edge at VCO is equal to the minimum time during which both outputs are disabled simultaneously. The minimum L voltage is 0.7 V. Reference Voltage The reference voltage source is a highly constant source with regard to its temperature behavior. It can be utilized in the external wiring of the op amp, the error comparators, the ramp generator, or other external components. Semiconductor Group 6 TDA 4714 C TDA 4716 C Block Diagram (TDA 4714 C) Semiconductor Group 7 TDA 4714 C TDA 4716 C Block Diagram (TDA 4716 C) Semiconductor Group 8 TDA 4714 C TDA 4716 C Absolute Maximum Ratings Parameter Symbol Limit Values min. Supply voltage Voltage at Q1, Q2 Current at Q1, Q2 Input RT Input CT Input RR Input CR Input comparator K2, K5, K7 Output K5 Input op amp TDA 4716 C Output op amp TDA 4716 C Reference voltage Input Csoft start Junction temperature Storage temperature Thermal resistance system - air Operating Range Supply voltage Ambient temperature Frequency VCO frequency Ramp generator frequency max. 33 33 70 - 0.3 - 0.3 - 0.3 - 10 - 0.3 - 0.3 - 0.3 - 0.3 - 0.3 - 0.3 - 55 7 7 7 10 33 33 33 V V mA V V V mA V V V V V V V C C K/W Unit Test Condition VS VQ IQ VI RT VI CT VI RR II CR VI K2, 5, 7 VQ K5 VI Op Amp VQ Op Amp VQ REF VI soft start Tj Tstg Rth SA - 0.3 - 0.3 Q1, Q2 high Q1, Q2 low VS - 1 max. 7 VREF 7 150 125 70 VS TA f fVCO fRG 10.5 - 25 40 40 40 30 85 100 250 250 V C kHz kHz kHz Semiconductor Group 9 TDA 4714 C TDA 4716 C Characteristics 11 V < VS < 30 V; - 25 C < TA < 85 C Parameter Symbol min. Supply current CT = 1 nF fVCO = 100 kHz Reference Reference voltage, TA = 25 C IREF = 1 mA, VS = 12 V Voltage change VS = 14 V 20 % Voltage change VS = 25 V 20 % Voltage change1) 0 mA < IREF < 5 mA Temperature coefficient Response threshold of IREF overcurrent Oscillator (VCO) Frequency range Frequency change VS = 14 V 20 % Frequency change VS = 25 V 20 % Tolerance RT = 0; CT = 0 Fall time sawtooth CT = 1 nF CT = 10 nF RC combination VCO 1) Limit Values typ. max. 20 Unit IS 8 mA VREF VREF VREF VREF 2.475 2.500 8 15 2.525 V mV mV 15 0.25 10 0.4 mV mV/K mA TC IREF f 40 0.5 -1 -7 100 f/f f/f f/f kHz % % % s s nF k 1 7 1 10 CT RT 0.82 5 47 700 Between 0 C and 70 C ambient temp. VREF is reduced to max. 5 mV. Semiconductor Group 10 TDA 4714 C TDA 4716 C Characteristics (cont'd) 11 V < VS < 30 V; - 25 C < TA < 85 C Parameter Symbol min. Ramp Generator Frequency range Maximum voltage at CR Minimum voltage at CR Input current through RR Current transformation ratio Comparator K2 Input current Turn-OFF delay time1) Input voltage Duty cycle D = 0 D = max Common-mode input voltage range Soft Start K3, K4 Charge current for Csoft start Discharge current for Csoft start Upper limiting voltage Switching voltage K4 Operational Amplifier (TDA 4716 C) Open-loop voltage gain Input offset voltage Temperature coefficient of VIO Input current Common-mode input voltage range Output current Rise time of output voltage Transition frequency Phase of fT Output voltage - 3 mA < I < 1.5 mA 1) Limit Values typ. max. Unit fRG VH VL IRR IRR/ICR 40 5.5 1.8 0 1/4 100 400 kHz V V A - IK2 tD OFF VI K2 1.8 5 2 500 A ns V V V VIC 0 5.5 Ich Idch Vlim VK4 6 2 5 1.5 A A V V GV0 VIO TC - II VIC IQ fT T 60 - 10 - 30 0 -3 80 10 30 2 5 1.5 1 3 120 V/t VQ H/L 1.5 5.5 dB mV V/K A V mA V/s MHz degr. V At the input: step function V = - 100 mV V = + 100 mV 11 Semiconductor Group TDA 4714 C TDA 4716 C Characteristics (cont'd) 11 V < VS < 30 V; - 25 C < TA < 85 C Parameter Symbol min. Output Stages Q1, Q2 Output voltage IQ = 20 mA Output leakage current VQH = 30 V Dynamic Current Limitation K7 Common-mode input voltage range Input offset voltage Input current Turn-OFF delay time2) Error detection time2) Overvoltage K5 Switching voltage Input current Turn-OFF delay time1) Error detection time1) Supply Undervoltage Turn-ON threshold for VS, rising Turn-ON threshold for VS, rising (0 C < TA < 70 C) Turn-OFF threshold for VS, falling Turn-ON threshold for VS, falling (0 C < TA < 70 C) 1) 2) Limit Values typ. max. Unit VQH VQL IQ 30 1.1 2 V V A VIC VIO - II tD OFF t 0 - 10 250 50 4 10 2 V mV A ns ns V - II VREF - 0.03 250 VREF + 0.03 V 2 tD OFF t A ns ns VS VS VS VS 8.8 11 10.5 10.5 10 V V V V 8.5 At the input: step function VREF = - 100 mV At the input: step function V = - 100 mV VREF = + 100 mV V = + 100 mV Semiconductor Group 12 TDA 4714 C TDA 4716 C Dimensioning Notes for RC Network 1. Determination of the minimum time during which both outputs must be disabled selection of CT; selection of CR CT. 2. Determination of the VCO frequency = 2 x output frequency selection of RT. 3. Determination of the rated slope of the rising ramp generator voltage, which the maximum possible turn-on period per half wave depends on selection of RR. 4. Duration of the soft start process selection of Csoft start 5. Wiring of the operational amplifier according to the dynamic requirements (TDA 4716 C). Semiconductor Group 13 TDA 4714 C TDA 4716 C Pulse Diagram Semiconductor Group 14 TDA 4714 C TDA 4716 C VCO Frequency versus RT and CT Semiconductor Group 15 TDA 4714 C TDA 4716 C VCO Temperature Response VS = 12 V; D = max. f VCO ---------------- [ 1 K ] with CT as parameter fK x K Semiconductor Group 16 |
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