Voltage Regulators AN8021NS External excitation flyback AC-DC switching power supply control IC ■ Overview Unit: mm 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. 5.01±0.20 5 8 +0.10 0.15 –0.05 4.30±0.20 6.40±0.20 (1.05) 0° to 10° 0.50±0.20 ■ 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 µA (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) +0.10 1.27 0.40 –0.05 1.75max. 4 0.10±0.10 1.45±0.10 1 0.10 Seating plane SOP008-P-0225C ■ Applications • Switching power supplies 2 V CC ■ Block Diagram RT OVP Start/Stop 4.2 V 6 5 VREF PWM Drive OSC OCL FB 1 8 Reset CLM 7 VOUT GND CLM 4 CT 3 IFB TIM/OVP 1 AN8021NS Voltage Regulators ■ Pin Descriptions Pin No. Symbol Description 1 VOUT Direct power MOSFET drive output 2 VCC Power supply. This pin monitored, and has threshold voltages for startup, stop, OVP reset, and other functions. 3 TIM/OVP 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 IFB Input for the current feedback signal provided from a photocoupler of the power supply output. 5 RT 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. 6 CT Connection for the capacitor used to generate the triangular wave. 7 CLM Pulse-by-pulse overcurrent protection input. Normally, an external filter is required. 8 GND Ground ■ Absolute Maximum Ratings Parameter Symbol Rating Unit Supply voltage VCC 35 V OVP pin allowable application voltage VOVP VCC V CLM pin allowable application voltage VCLM − 0.3 to +7.0 V Supply current ICC mA Steady-state output current IO +150 mA Peak output current IOP ±1 000 mA IFB pin allowable application current IFB −5 mA PD 122 mW Topr −30 to +85 °C Tstg −55 to +150 °C Power dissipation *2 Operating temperature Storage temperature Notes) 2 *1 *1 1. *1: Items other than the storage temperature and operating temperature are all stipulated for an ambient temperature Ta = 25°C. *2: Applies when Ta = 85°C 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. Voltage Regulators AN8021NS ■ Recommended Operating Range Parameter Symbol Range Unit VCC The stop voltage to 34 V Supply voltage ■ Electrical Characteristics at Ta = 25°C Parameter Symbol Conditions Min Typ Max Unit Start voltage STRT VCC 13.0 14.2 15.4 V Stop voltage STOP VCC 8.5 9.2 9.9 V Standby mode bias current STB ICC VCC = 12 V 50 70 105 µA Operating bias current OPR ICC VCC = 34 V 5.9 7.8 9.6 mA OVP operating bias current 1 OVP1 ICC VCC = 20 V 2.4 3.0 3.6 mA OVP operating bias current 2 OVP2 ICC VCC = 10 V 0.44 0.55 0.66 mA OVP operating threshold voltage CVP VTH VCC = 18 V 5.4 6.0 6.6 V 7.6 8.4 9.2 V −15 −25 −35 µA OVP release supply voltage OVPC VCC Timer latch charge current TIM ICH VCC = 18 V, RT = 19 kΩ Timer latch start feedback current TIM IFB VCC = 18 V Overcurrent protection threshold voltage CLM VTH VCC = 18 V Pre-startup low-level output voltage STB VOL Low-level output voltage High-level output voltage − 0.37 − 0.5 − 0.63 mA -180 -200 -220 mV VCC = 12 V, IO = 10 mA 0.8 1.8 V VOL VCC = 18 V, IO = 100 mA 1.3 1.8 V VOH VCC = 18 V, IO = −100 mA 15.0 16.5 V * fOSC1 VCC = 18 V 170 180 190 kHz Maximum duty factor Dmax VCC = 18 V 62 66 70 % Feedback current at 0% duty Dmin. IFB VCC = 18 V −1.1 −1.5 −1.9 mA Feedback current at maximum duty Dmax. IFB VCC = 18 V Oscillator frequency − 0.37 − 0.5 − 0.63 mA Note ) *: Provisional rating • Design reference data Note) The characteristics listed below are theoretical values based on the IC design and are not guaranteed. Parameter Symbol Conditions Min Typ Max Unit fOSC2 Ta = −30°C to +85°C, VCC = 18 V 160 240 kHz Overcurrent protection delay time CLM tDLY VCC = 18 V, no load. 200 ns Oscillator frequency 2 Output voltage rise time tr VCC = 18 V, no load. 50 ns Output voltage fall time tf VCC = 18 V, no load. 25 ns 3 AN8021NS Voltage Regulators ■ Application Circuit Example AC 2 VCC 15 V Zener diode 68 kΩ 1 kΩ TIM/ 0.22 µF OVP 3 220 pF CT 6 19 kΩ RT 5 OVP Start/Stop 100 µF VREF 4.2 V PWM Drive OSC OCL FB IFB 4 33 Ω 8 GND Reset CNCIS101(ON3131 *) etc. 1 VOUT CLM 7 CLM 130 Ω 220 Ω 2 200 pF 0.47 Ω PC 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 ■ 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