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TEA5170 датащи(PDF) 4 Page - STMicroelectronics |
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TEA5170 датащи(HTML) 4 Page - STMicroelectronics |
4 / 9 page ELECTRICAL CHARACTERISTICS (TA = 25 oC, VCC = 12V, unless otherwise specified) (continued) Symbol Parameter Test Conditions Min. Typ. Max. Unit VCC MONITOR VSTART Turn-on Threshold 3.60 4 4.40 V VHYST Hysteresis Voltage 100 mV VSTOP Turn-off Threshold 3.50 V TOTAL DEVICE ICC Supply Current RT = 100k Ω ± 0%, CT = 1.2nf ± 0% No Load on Pin 3, VCC = 12V 712 25 mA GENERAL DESCRIPTION The TEA5170 takes place in the secondary part of an isolated off-line SMPS. During normal mode operation, it sends pulses to the slave circuit lo- cated in the primary side (TEA2164, TEA2260/61) through a pulse transformer to achieve a very precisely regulated voltage by duty cycle control. The main blocs of the circuit are : - an error voltage amplifier - an RC oscillator - an output stage -a VCC monitor - a voltage reference bloc - a pulse width modulator - two logic blocs - a soft start and Duty cycle limiting bloc PRINCIPLE OF OPERATION The TEA5170 sends pulses continuously to the slave circuit in order to insure a proper behaviour of the primary side. - According to this, the output duty cycle is varying between DON (min.) (0.05) and DON (max.) (0.75) : then even in case of open load, pulses are still sent to the slave circuit. MASTER CIRCUIT SLAVE CIRCUIT PWM MASTER-SLAVE ARCHITECTURE Figure 1 : Basic Concept ASYNCHRONIZED MODE (Figure 2) The regulated voltage image is compared to 2V vol-tage reference. The error voltage amplifier out- put and the RC oscillator voltage ramp are applied to the internal Pulse Width Modulator Inputs. The PWM logic Output is connected to a logic bloc which behaves like a RS latch, sets by the PWM output and resets when Ct downloading occurs. Finally, the push-pull output bloc delivers square wave signal whom output leading edge occurs during Ct uploading time, and output trailing edge at Ct downloading time end. The duty cycle is limited to 75% of oscillator period as maximum value and to Ct downloading time/oscillator period as minimum value (Figure 2). OSCILLATOR RAMP V1 POWER OUTPUT V T1 t max. T2 = Ton min. V2 Ton max. Figure 2 SYNCHRONIZED MODE (see Figure 3) The TEA5170 will enter the Synchronized Mode when it receives one pulse through Rt during Ct discharge. At that time Ct charging current will be multiplied by 0.75 and period will increase up to To x 1.26. A pulse occuring during the synchro window, com- mands the Ct downloading. If none, the TEA5170 will return to normal mode at the end of the period. TEA5170 4/9 |
Аналогичный номер детали - TEA5170 |
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Аналогичное описание - TEA5170 |
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