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| Voltage Regulators AN8021NS External excitation flyback AC-DC switching power supply control IC s Overview The AN8021S is a switching power supply control IC that controls the power supply from the primary side. It is optimal for relatively small switching power supplies. All rarely used functions have been removed from the AN8021S and as a result it is an extremely easy-to-use compact device. Furthermore, internal settings are implemented as many as we can, cost cut is possible with reduced external parts. 5.010.20 Unit: mm 8 5 (1.05) 4.300.20 6.400.20 0.15 -0.05 +0.10 0 to 10 0.500.20 1 4 0.100.10 1.450.10 1.75max. s Features * Supports operation at switching frequencies up to 700 kHz and achieves a 35 ns output rise time and a 25 ns output fall time. * Extremely low pre-startup current consumption of 70 A (typical) allows a significantly smaller startup resistor to be used. * Totem pole circuit structure adopted in the output block. * Output current absolute maximum rating of 1.0 A (peak) for direct driving of power MOSFET. * Pulse-by-pulse overcurrent protection circuit * Low voltage malfunction prevention circuit On/off: 14.2 V/9.2 V * Timer latch and overvoltage protection functions * Package: SONF-8D (0.60) 1.27 0.10 Seating plane 0.40 -0.05 +0.10 SOP008-P-0225C s Applications * Switching power supplies s Block Diagram 2V CC TIM/OVP 3 OVP Start/Stop VREF 4.2 V OSC OCL FB PWM Drive CT RT 6 5 1 8 VOUT GND CLM Reset CLM 7 IFB 4 1 AN8021NS s Pin Descriptions Pin No. 1 2 3 Symbol VOUT VCC TIM/OVP Direct power MOSFET drive output Description Voltage Regulators Power supply. This pin monitored, and has threshold voltages for startup, stop, OVP reset, and other functions. OVP (overvoltage protection) and timer latch functions. OVP: Accepts a power supply overvoltage detection signal. When a high-level signal is input, internal circuits are turned off and this state is latched. To reset this OVP latched state, the VCC voltage should be lowered to below the release voltage. Timer latch: The IC detects output voltage drops due to overcurrent states in the power supply output by monitoring the magnitude of the current input to the IFB pin. In particular, when the current IIFB has fallen below a certain level, a charge current flows into the capacitor connected to this pin externally. When that capacitor is charged to the OVP threshold voltage, OVP operates and the IC keeps a stopped state. 4 5 6 7 8 IFB RT CT CLM GND Input for the current feedback signal provided from a photocoupler of the power supply output. Connection for the resistor that determines the charge and discharge currents of the triangular wave. In this device, the charge and discharge currents are the same. Connection for the capacitor used to generate the triangular wave. Pulse-by-pulse overcurrent protection input. Normally, an external filter is required. Ground s Absolute Maximum Ratings Parameter Supply voltage OVP pin allowable application voltage CLM pin allowable application voltage Supply current Steady-state output current Peak output current IFB pin allowable application current Power dissipation *2 *1 Symbol VCC VOVP VCLM ICC IO IOP IFB PD Topr Tstg Rating 35 VCC - 0.3 to +7.0 +150 1 000 -5 122 -30 to +85 -55 to +150 Unit V V V mA mA mA mA mW C C Operating temperature Storage temperature Notes) *1 1. *1: Items other than the storage temperature and operating temperature are all stipulated for an ambient temperature Ta = 25C. *2: Applies when Ta = 85C for the independent IC without a heat sink. 2. Currents or voltages may not be applied to any pins not stipulated above. For circuit currents, a positive (+) value indicates current flowing into the IC, and a negative (-) value indicates current flowing out of the IC. 2 Voltage Regulators s Recommended Operating Range Parameter Supply voltage Symbol VCC Range The stop voltage to 34 AN8021NS Unit V s Electrical Characteristics at Ta = 25C Parameter Start voltage Stop voltage Standby mode bias current Operating bias current OVP operating bias current 1 OVP operating bias current 2 OVP operating threshold voltage OVP release supply voltage Timer latch charge current Timer latch start feedback current Overcurrent protection threshold voltage Pre-startup low-level output voltage Low-level output voltage High-level output voltage Oscillator frequency * Symbol STRT VCC STOP VCC STB ICC OPR ICC OVP1 ICC OVP2 ICC CVP VTH OVPC VCC TIM ICH TIM IFB Conditions Min 13.0 8.5 Typ 14.2 9.2 70 7.8 3.0 0.55 6.0 8.4 -25 Max 15.4 9.9 105 9.6 3.6 0.66 6.6 9.2 -35 Unit V V A mA mA mA V V A mA mV V V V kHz % mA mA VCC = 12 V VCC = 34 V VCC = 20 V VCC = 10 V VCC = 18 V VCC = 18 V, RT = 19 k VCC = 18 V VCC = 12 V, IO = 10 mA VCC = 18 V, IO = 100 mA VCC = 18 V, IO = -100 mA VCC = 18 V VCC = 18 V VCC = 18 V 50 5.9 2.4 0.44 5.4 7.6 -15 - 0.37 - 0.5 - 0.63 -180 15.0 170 62 -1.1 -200 0.8 1.3 16.5 180 66 -1.5 -220 1.8 1.8 190 70 -1.9 CLM VTH VCC = 18 V STB VOL VOL VOH fOSC1 Dmax Dmin. IFB Maximum duty factor Feedback current at 0% duty Feedback current at maximum duty Note ) *: Provisional rating Dmax. IFB VCC = 18 V - 0.37 - 0.5 - 0.63 * Design reference data Note) The characteristics listed below are theoretical values based on the IC design and are not guaranteed. Parameter Oscillator frequency 2 Symbol fOSC2 Conditions Ta = -30C to +85C, VCC = 18 V VCC = 18 V, no load. VCC = 18 V, no load. Min 160 Typ 200 50 25 Max 240 Unit kHz ns ns ns Overcurrent protection delay time CLM tDLY VCC = 18 V, no load. Output voltage rise time Output voltage fall time tr tf 3 AN8021NS s Application Circuit Example Voltage Regulators 68 k 2 VCC AC 1 k 15 V Zener diode TIM/ 0.22 F OVP 3 100 F OVP Start/Stop VREF 33 220 pF 19 k CT 6 RT 5 OSC OCL 4.2 V FB PWM Drive 1 VOUT 8 GND Reset IFB 4 CLM 7 CLM 130 0.47 PC 220 2 200 pF CNCIS101(ON3131 *) etc. Note) 1. The external circuits and circuit constants are provided as an example of a possible design. No guarantees are made with respect to these items for use in mass produced end products. 2. *: Former part number s Usage Notes 1. Direct connection with the power supply pin (shorting to VCC) In this device, pins other than pin 3 cannot be connected directly to the power supply pin (pin 2). Connection of any other pins to VCC will result in permanent damage to the device. 2. Direct connection with the ground pin (shorting to ground) In this device, pin 1 cannot be connected directly to the ground pin (pin 8). Connection of this pin to ground will result in permanent damage to the device. 4 |
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