CMOS IC(For Switching Power Supply Control)

FA13842,13843,13844,13845 s Description The FA1384X series are CMOS current mode control ICs for off-line and DC-to-DC converters. These ICs can reduce start-up circuit loss and are optimum for high efficiency power supplies because of the low power dissipation achieved through changes in the CMOS fabrication process. These ICs can drive a power MOSFET directly. The high-performance, compact power supply can be designed with minimal external components . CMOS IC FA13842, 13843, 13844, 13845 For Switching Power Supply Control s Dimensions, mm SOP-8 8 5 1 4 4.9 +0.1 –0.05 s Features • • • • • • • CMOS process Low-power dissipation Standby current 2µA (max.), start-up current 30µA (max.) Pulse-by-pulse current limiting 5V bandgap reference UVLO (Undervoltage lockout) with hysteresis Maximum duty cycle FA13842, 13843: 96% FA13844, 13845: 48% • Pin-for-pin compatible with UC384X Note: Pins are fully compatible, but characteristics are not. When our ICs are applied to a power supply circuit designed for other manufactures' 384X series, the characteristics and safety features of the power supply must be checked. 6.0±0.2 3.9 0.4±0.1 1.27±0.2 DIP-8 8 5 s Types of FA1384X series Type UVLO Start threshold Stop threshold FA13842P 16.5V±1V 9V±1V FA13842N FA13843P 9.6V±1V 9V±1V FA13843N FA13844P 16.5V±1V 9V±1V FA13844N FA13845P FA13845N 9.6V±1V 9V±1V Maximum duty Package cycle 96% DIP SOP 96% DIP SOP 48% DIP SOP 48% DIP SOP 1 9.3 1.5 4 6.4 3.0min 4.5max 3.3 0~8° 0.05 0.25 – +0.1 7.62 2.54±0.25 0.46±0.1 0~15 ˚ 0~1 5˚ 1.7max 0.20 1 FA13842, 13843, 13844, 13845 s Block diagram FA13842, 13843 VCC 7 30V UVLO OUTPUT ENB Pin No. Symbol Function 1 COMP Compensating UVLO VCC 5V REF ENB 2.5V 8 VREF 2 3 4 FB ISNS RT/CT 6 OUT RT/CT 4 ER AMP FB 2 COMP 1 ISNS 3 2R 1R OSC 5 GND 1V S Q FF R QB 5 6 7 8 GND OUT VCC VREF 5V Controlled block FA13844, 13845 VCC 7 30V UVLO OUTPUT ENB Description Error amplifier output, available for loop compensation circuit Feedback Inverting input of the error amplifier Current sensing Input voltage proportional to inductor current Oscillator control Setting oscillation frequency and maximum duty-cycle with resistor RT and capacitor CT Ground Ground Output Output for driving a power MOSFET Power supply Power supply Reference voltage Reference voltage and current source charging capacitor C T through resistor RT UVLO VCC 5V REF ENB 2.5V 8 VREF 6 OUT RT/CT 4 ER AMP FB 2 COMP 1 ISNS 3 2R 1R OSC 5 GND 1V S Q FF R QB TFFQ CLK QB 5V ControlIed block s Absolute maximum ratings (Ta=25˚C) Item Supply voltage Zener current Output peak current FB/ISNS terminal input voltage Error amplifier sink current Total power dissipation Thermal resistance Junction temperature Ambient temperature Storage temperature Symbol VCC IZ IO VIN I SINK Pd Rθ j-a Tj Ta Tstg Test condition Low impedance source Zener clamp (Icc<10mA) Source current Sink current FB, ISNS at Ta < 50˚C Junction-air DIP SOP DIP SOP Rating 28 Self limiting 10 400 1 –0.3 to 5.3 10 800 400 125 250 150 –25 to 85 –40 to 150 Unit V V mA mA A V mA mW ˚C/W ˚C ˚C ˚C 2 FA13842, 13843, 13844, 13845 s Recommended operating conditions Item Supply voltage Oscillation timing capacitor Oscillation timing resistor Oscillation frequency Symbol VCC CT RT fOSC Min. 10 0.47 2.0 10 Max. 25 10 100 500 Unit V nF kΩ kHz s Electrical characteristics (Vcc=15V, RT=10kΩ, CT=3.3nF, Ta=25˚C) Reference voltage section Item Reference voltage Line regulation Load current regulation Temperature regulation Output current at short-circuit Symbol VREF LINE LOAD VTC IOS Test condition Tj=25˚C, IL=1mA Vcc=10 to 25V IL=0 to 20mA Ta=–25 to 85˚C Tj=25˚C Min. 4.75 Typ. 5.00 ±3 ±3 ±0.3 60 Max. 5.25 ±20 ±25 Unit V mV mV mV/˚C mA Oscillator section Item Oscillation frequency Voltage stability Temperature stability Oscillation amplitude Discharge current Symbol fOSC fdv fdt VOSC IDISCHG Test condition Tj=25˚C Ta=–25 to 85˚C Vcc=10 to 25V Ta=–25 to 85˚C Tj=25˚C Tj=25˚C Min. 49 47 Typ. 52 ±0.25 –0.07 1.6 8.4 Max. 55 57 ±1 Unit kHz kHz % %/˚C V mA Error amplifier section Item Input voltage Input leak current Open-loop gain Unity gain bandwidth Output source current Output sink current Output voltage Symbol VFB IFB AV fT ISOURCE ISINK VH COMP VL COMP Test condition COMP=2.5V, Tj=25˚C Min. 2.4 65 0.7 –0.8 2 4.0 Typ. 2.5 72 1 –1.0 15 4.5 80 Max. 2.6 ±2 Unit V µA dB MHz mA mA V mV FB=2.3V, COMP=0V FB=2.7V, COMP=1V FB=2.3V, RL=15kΩ to GND FB=2.7V, RL=15kΩ to VREF 500 Current sensing section Item Voltage gain Maximum input signal Input bias current Delay to output Symbol AV IS VTH IS IIS TPD Test condition Tj=25˚C FB=0V Tj=25˚C, ISNS to OUT Min. 2.85 0.9 Typ. 3 1.0 –1 150 Max. 3.15 1.1 –5 300 Unit V/V V µA ns 3 FA13842, 13843, 13844, 13845 Output section Item High-level output Low-level output Rise time Fall time Symbol VOH VOL tr tf Test condition I source=–20mA I source=–100mA I sink=20mA I sink=200mA CL=1nF, Tj=25˚C CL=1nF, Tj=25˚C Min. 14.5 12 Typ. 14.75 13.5 0.15 1.5 40 20 Max. Unit V V V V ns ns 0.3 3 150 150 Under-voltage lockout section Item Start threshold Min. operating voltage Hysteresis Symbol VTH ON VTH OFF VHYS Test condition FA13842, 13844 FA13843, 13845 FA13842, 13844 FA13843, 13845 Min. 15.5 8.6 8 Typ. 16.5 9.6 9 7.5 0.6 Max. 17.5 10.6 10 Unit V V V V V PWM section Item Maximum duty cycle Minimum duty cycle Symbol Dmax Dmin Test condition FA13842, 13843 FA13844, 13845 FB=5V, COMP=Open Min. 94 47 Typ. 96 48 Max. 98 50 0 Unit % % % Overall device Item Standby current Start-up current Operating current Zener voltage (Vcc) Symbol I CCL I CC ST I CC OP VZ Test condition FA13842, 13844 Vcc=14V FA13843, 13845 Vcc=7V Vcc=Start threshold Icc=5mA Min. Typ. Max. 2 2 30 5 34 Unit µA µA µA mA V 28 12 3 30 4 FA13842, 13843, 13844, 13845 s Characteristic curves (Ta=25˚C) Timing resistance vs. oscillation frequency FA13842, FA13843 100 Output dead time vs. oscillation frequency FA13842, FA13843 100 VCC= 15V Ta= 25˚C 470pF 2.2nF CT=10nF 10 2.2nF CT=10nF RT resistance (kΩ) 470pF Output dead time (%) 10 VCC= 15V Ta= 25˚C 1 1 10 100 Oscillation frequency (kHz) 1000 1 10 100 Oscillation frequency (kHz) 1000 Timing resistance vs. oscillation frequency FA13844, FA13845 100 470pF 2.2nF Output dead time vs. oscillation frequency FA13844, FA13845 100 VCC= 15V Ta= 25˚C 90 Output dead time (%) CT=10nF RT resistance (kΩ) 80 10 70 2.2nF CT=10nF 60 470pF VCC= 15V Ta= 25˚C 1 50 40 1 10 100 Oscillation frequency (kHz) 1000 10 100 Oscillation frequency (kHz) 1000 RT/CT discharge current vs. temperature 10 Output max. duty cycle vs. timing resistance FA13842, FA13843 100 Output maximum duty cycle (%) 90 80 70 60 RT/CT discharge current (mA) 9.5 9 8.5 8 7.5 50 40 7 –50 0 50 Temperature (˚C) 100 150 1 2 5 RT timing resistance (kΩ) 10 5 FA13842, 13843, 13844, 13845 ISNS threshold voltage vs. COMP voltage 1200 VCC= 15V FB= 0V OUT= off COMP source current (µA) 0 1 3 2 COMP voltage (V) 4 5 COMP source current vs. COMP voltage 0 1000 ISNS threshold voltage (mV) –200 800 –400 600 –600 400 –800 200 –1000 0 –1200 0 1 3 2 COMP voltage (V) 4 5 COMP to ISNS offset voltage vs. temperature 2.5 COMP source current vs. temperature –800 VCC= 15V COMP= 0V COMP to ISNS offset voltage (V) 2 COMP source current (µA) 0 50 Temperature (˚C) 100 150 –900 –1000 1.5 –1100 1 –1200 0.5 –1300 0 –50 –1400 –50 0 50 Temperature (˚C) 100 150 Error amp open loop voltage gain and phase vs. frequency 100 80 60 40 Gain 20 0 –20 –40 10 180 Phase Phase ( ˚) 0 VREF short circuit current vs. temperature 80 VCC= 15V VREF= 0V VREF short circuit current (mA) 70 Open loop voltage gain (dB) 60 50 40 30 100 1.0k 10k 100k Frequency (Hz) 1.0M 10M 20 0 50 Temperature (˚C) 100 150 6 FA13842, 13843, 13844, 13845 VCC supply current vs. VCC supply voltage 8 7 6 VCC current (mA) 5 4 3 2 13843/45 1 0 RT= 10kΩ CT= 3.3nF OUT= No load VCC startup current (µA) 14 Ta= 25˚C 12 10 8 6 4 2 0 14 VCC startup current vs. VCC supply voltage FA13842, FA13844 13842/44 0 10 20 VCC voltage (V) 30 14.5 15 15.5 16 VCC voltage (V) 16.5 17 Output waveform Vcc=15V, OUT CL=1nF, Ta=25˚C Vcc=15V, OUT CL=2.2nF, Ta=25˚C VCC= 15V OUT CL= 1nF Ta= 25˚C VCC= 15V OUT CL= 2.2nF Ta= 25˚C 2.50V 25.0ns 2.50V 50.0ns 7 FA13842, 13843, 13844, 13845 s Description of each circuit 1. Oscillator The oscillation frequency is determined by timing resistance RT and timing capacitor CT, which are connected to RT/CT terminal. CT is charged to about 3V through RT from a 5V reference, and discharged to about 1.4V by the built-in discharge circuit. (See Fig. 1, 2, 3.) Blanking pulses are generated in the IC during the CT discharge period. The output is fixed in the “low” state by these pulses, and a fixed dead time is produced. See the characteristic curves on page 45 for the oscillation frequency, RT and CT. In the case of FA13844/45, a flip-flop causes the output to be blanked with every other cycle. Therefore, the switching frequency of a power MOSFET is 1/2 of the oscillation frequency determined by RT and CT . (See Fig. 3.) Vcc Vin VCC 7 30V UVLO ENB 2.5V OUTPUT ENB 6 OUT RT RT/CT CT 4 5 GND RS OSC ER AMP 2R 1R FB 2 COMP 1 ISNS 3 1V S Q FF R QB 2. Error amplifier Inverting input and output are connected to the FB terminal and COMP terminal, respectively. A 2.5V reference is connected internally to the non-inverting input. The output voltage is offset by a diode VF voltage (=0.7V) and divided by three. The divided voltage is connected to the input of the current sensing comparator. Fig. 1 3V CT 1.4V 3. Current sensing comparator and PWM latch The “High” state of the OUT terminal begins at the time CT starts charging. The OUT terminal turns to “Low” when the peak