AN8028AN8028, elektronika, A ukł scsalone
[ Pobierz całość w formacie PDF ]
Voltage Regulators AN8028 Self-excited RCC pseudo-resonance type AC-DC switching power supply control IC Unit: mm 2.4±0.25 3.3±0.25 Overview The AN8028 is an IC developed for controlling the self-excited switching power supply employing the RCC pseudo-resonance type control method. It is compact, equipped only with the necessary mini- mum functions. The maximum on-period and the minimum off-pe- riod can be set separately by using the external capacitor and resistor respectively. It is suitable for the power supply of AV equipment. 6.0±0.3 9 8 7 6 5 4 3 2 1 Features · Operating supply voltage range: Stop voltage (8.6 V typical) to 34 V · Output block employs the totem pole system. · Power MOSFET can be directly driven. (output peak current: ±1 A maximum) · Small pre-start operating current (95 mA typical) allows using a small size start resistor. · Built-in pulse-by-pulse overcurrent protection function · Incorporating the protection circuit against malfunction at low voltage (start/stop: 14.9 V/8.6 V) · Built-in overvoltage protection function (externally resettable) · Built-in timer latch function · Equipped with frequency (VF) control function. · 9-pin single inline package expands the freedom of board design 0.3 +0.1 –0.05 3.0±0.3 SIP009-P-0000C Applications · Televisions, facsimiles, printers, scanners, video equipment n Block Diagram Signal U.V.L.O. V REF (7.1 V) 8. V 1. V Current source TIM/OVP 8 Switch diode TIM 9 I FB Q Q 6 FB IN IN V OUT RS latch 0.1 V 5 GND R 1 TDL 4 CLM CLM Low-side clamp 0 V High-side clamp 2.8 V S 0.32 V 0.7 V 1 n n n AN8028 Voltage Regulators n Pin Descriptions Pin No. Symbol Description 1 TDL Transformer reset detection 2 TOFF Pin for connecting C and R to set minimum off-period 3 TON Pin for connecting C to set minimum on-period 4 CLM Input pin for overcurrent protection detection 5 GND Grounding pin 6 V OUT Output pin 7 V CC Power supply voltage pin 8 TIM/OVP Pin for use both overvoltage protection circuit and timer latch 9 FB Photocoupler connection pin for error voltage feedback n Absolute Maximum Ratings Parameter Symbol Rating Unit Supply voltage V CC 35 V Peak output current I 6PEAK ±1 A Power dissipation P D 874 mW Operating ambient temperature * T opr -30 to +85 °C Storage temperature * T stg -55 to +150 °C Note) * : Expect for the operating ambient temperature and storage temperature, all ratings are for T a = 25°C. n Recommended Operating Range Parameter Symbol Range Unit Supply voltage V CC From stop voltage to 34 V n Electrical Characteristics at V CC = 18 V, T a = 25 C Parameter Symbol Conditions Min Typ Max Unit U.V.L.O. start supply voltage V 7START 13.4 14.9 16.4 V U.V.L.O. operation stop supply voltage V 7STOP 7.7 8.6 9.5 V U.V.L.O. start to stop supply voltage DV 7 5.7 6.3 6.9 V OVP operation threshold voltage V 8OVP 6.1 7.3 8.5 V OVP release voltage V 7OVP 7.4 8.2 9 V OVP operating circuit current 1 I 7OVP1 V CC = 9.1 V, V OVP = 8.5 V 0.56 0.79 1.02 mA OVP operating circuit current 2 I 7OVP2 V CC = 20 V, V OVP = 8.5 V 5.9 7.7 9.5 mA TDL threshold voltage V 1TDL 0.22 0.32 0.42 V TDL upper limit clamp voltage V 1TDL/H I TDL = 3mA 2 2.8 3.6 V TDL lower limit clamp voltage V 1TDL/L I TDL = -3mA - 0.3 0 0.3 V CLM threshold voltage V 4CLM -220 -200 -180 mV 2 ° Voltage Regulators AN8028 n Electrical Characteristics at V CC = 18 V, T a = 25 C (continued) Parameter Symbol Conditions Min Typ Max Unit TON maximum on-period current I 3TON FB terminal = open -135 -110 -85 mA TON terminal = GND TON upper limit voltage V 3TON/H FB terminal = open 0.55 0.7 0.85 V TON lower limit voltage V 3TON/L FB terminal = open - 0.1 0.05 0.2 V TOFF upper limit voltage V 2TOFF/H 0.7 0.9 1.1 V TOFF lower limit voltage V 2TOFF/L - 0.1 0.05 0.2 V Output oscillation frequency f OSC C ON = 2 200 pF, R OFF = 1.5 kW 55 65 75 kHz C OFF = 1 000 pF Output current feedback current gain G IFB I FB = -1 mA 5.05 6.8 8.55 ¾ Pre-start low-level output voltage V 6STB/L V CC = 10 V, I OUT = 10 mA ¾ 1 1.25 V Low-level output voltage 1 V 6L(1) I OUT = 10 mA ¾ 0.9 2 V Low-level output voltage 2 V 6L(2) I OUT = 100 mA ¾ 1.1 2.2 V High-level output voltage 1 V 6H(1) I OUT = -10 mA 15.7 16.5 ¾ V High-level output voltage 2 V 6H(2) I OUT = -100 mA 15.5 16.3 ¾ V Pre-start circuit current I 7STB V CC = 12V 55 95 135 mA Circuit current 1 I 7OPR(1) V CC = 18 V 8.55 11.5 14.3 mA TON terminal = GND FB terminal = open Circuit current 2 I 7OPR(2) V CC = 34 V 9.6 12.5 15.4 mA TON terminal = GND FB terminal = open TDL flowing-out current I 1TDL V TDL = 0.5 V -5 0 ¾A n Terminal Equivalent Circuits Pin No. Equivalent circuit Description I/O 1 V REF TDL: I Transformer reset detection terminal. When the transformer reset is detected and low is inputted into the terminal, the output of the IC (V OUT ) becomes high. However, low-level sig- nal under the minimum off-period determined by the T OFF is ignored. 1 High- side clamp Low- side clamp 2 TOFF: ¾ V CC Terminal for connecting the resistor and capaci- tor for determining the minimum off-period (low) of the IC output (V OUT ). An equation for approximate calculation of the minimum off-period (T OFF ) is as follows: T OFF Comp. 0.1 V 2 = 2.2 R C: External capacitance R: External resistance ´ C ´ 3 ° AN8028 Voltage Regulators n Terminal Equivalent Circuits (continued) Pin No. Equivalent circuit Description I/O 3 TON: ¾ V REF V CC Terminal for connecting the capacitor for deter- mining the maximum on-period (high) of the IC output (V OUT ). An equation for approximate calculation of the maximum on-period (T ON ) is as follows: T ON = 6 500 ´ C C: External capacitance Comp. 0.7 V 3 FB 4 CLM: I V REF Input terminal for detection of the pulse-by- pulse overcurrent protection. Normally, it is recommended that a filter be attached externally. Comp. 4 (-) 5 GND: ¾ 5 Grounding terminal. 6 V CC V OUT : O Output terminal for directly driving the power MOSFET. It uses the totem pole type output. The maximum rating of the output current: Peak: ±1 A DC: ±150 mA 6 7 V CC : ¾ 7 Terminal for applying power supply voltage. It monitors the supply voltage and has the opera- tion threshold of start/stop/OVP reset. 4 Voltage Regulators AN8028 n Terminal Equivalent Circuits (continued) Pin No. Equivalent circuit Description I/O 8 TIM/OVP: I V CC Terminal for use both OVP (overvoltage protec- tion circuit) and timer latch. [OVP] When overvoltage signal of the power supply is detected and high is inputted to the terminal, it turns off the internal circuit. At the same time, it holds that condition (latch). To reset the OVP latch, the V CC should be decreased to a voltage lower than the release voltage. [Timer latch] It detects the output voltage fall due to the overcurrent condition of the power supply out- put through the current level inputted to IFB. When the I IFB decreases under the current of certain value, the charge current flows in the capacitor which is connected to this terminal. Then, when the capacitor is charged up to the threshold voltage of the OVP, the OVP works so that the IC could keep the operation stop condi- tion. Comp. 7.3 V 5 mA 8 9 V CC FB: I Terminal for connecting the photocoupler for error voltage feedback of the power supply out- put. It is possible to cancel about 180 mA of the dark current of photocoupler. TON 9 Application Notes [1] Operation descriptions 1. Start/stop circuit block · After AC rectification Start resistance R1 Start mechanism When AC voltage is applied and the supply voltage reaches the start voltage through the current from start resistor, the IC starts opera- tion. Then the power MOSFET driving starts. Thereby, bias is generated in the transformer and the supply voltage is given from the bias coil to the IC. (This is point a in figure 1 ) During the period from the time when the start voltage is reached and the voltage is gen- erated in the bias coil to the time when the IC is provided with a sufficient supply voltage, the supply voltage of the IC is supplied by the capacitor (C8) connected to V CC . V CC V OUT GND C8 Before start Start Voltage supplied from bias coil Start voltage Stop voltage a Start condition b c Start failure Figure 1 5 n [ Pobierz całość w formacie PDF ] |
Podobne
|