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TL5001A-Q1 Folha de dados(PDF) 3 Page - Texas Instruments |
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TL5001A-Q1 Folha de dados(HTML) 3 Page - Texas Instruments |
3 / 19 page DETAILED DESCRIPTION VOLTAGE REFERENCE ERROR AMPLIFIER To PWM Comparator Vref = 1 V 4 VI(FB) 3 + − R2 R1 COMP FB Compensation Network TL5001/A GND 8 OSCILLATOR/PWM DEAD-TIME CONTROL (DTC) R DT + (Rt ) 1250) [D(Vosc max * Vosc min) ) Vosc min] V RT ; V RT + 1 V (1) TL5001A-Q1 www.ti.com .............................................................................................................................................. SLVS603B – AUGUST 2005 – REVISED FEBRUARY 2009 A 2.5-V regulator operating from VCC is used to power the internal circuitry of the TL5001A and as a reference for the error amplifier and SCP circuits. A resistive divider provides a 1-V reference for the error amplifier noninverting input which typically is within 2% of nominal over the operating temperature range. The error amplifier compares a sample of the dc-to-dc converter output voltage to the 1-V reference and generates an error signal for the PWM comparator. The dc-to-dc converter output voltage is set by selecting the error-amplifier gain (see Figure 1), using the following expression: VO = (1 + R1/R2) (1 V) Figure 1. Error-Amplifier Gain Setting The error-amplifier output is brought out as COMP for use in compensating the dc-to-dc converter control loop for stability. Because the amplifier can only source 45 µA, the total dc-load resistance should be 100 kΩ or more. The oscillator frequency (fosc) can be set between 20 kHz and 500 kHz by connecting a resistor between RT and GND. Acceptable resistor values range from 15 k Ω to 250 kΩ. The oscillator frequency can be determined by using the graph shown in Figure 5. The oscillator output is a triangular wave with a minimum value of approximately 0.7 V and a maximum value of approximately 1.3 V. The PWM comparator compares the error-amplifier output voltage and the DTC input voltage to the triangular wave and turns the output transistor off whenever the triangular wave is greater than the lesser of the two inputs. DTC provides a means of limiting the output-switch duty cycle to a value less than 100%, which is critical for boost and flyback converters. A current source generates a reference current (IDT) at DTC that is nominally equal to the current at the oscillator timing terminal (RT). Connecting a resistor between DTC and GND generates a dead-time reference voltage (VDT), which the PWM/DTC comparator compares to the oscillator triangle wave as described in the previous section. Nominally, the maximum duty cycle is 0% when VDT is 0.7 V or less and 100% when VDT is 1.3 V or greater. Because the triangle wave amplitude is a function of frequency and the source impedance of RT is relatively high (1250 Ω), choosing RDT for a specific maximum duty cycle (D) is accomplished using the following equation and the voltage limits for the frequency in question as found in Figure 11 (Voscmax and Voscmin are the maximum and minimum oscillator levels): Where RDT and Rt are in Ω, D is in decimal Copyright © 2005–2009, Texas Instruments Incorporated Submit Documentation Feedback 3 Product Folder Link(s): TL5001A-Q1 |
Nº de peça semelhante - TL5001A-Q1_15 |
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Descrição semelhante - TL5001A-Q1_15 |
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