R1282D002A-TR

2CH PWM DC/DC CONTROLLER R1282D002A SERIES OUTLINE NO. EA-086-0502 The R1282D002A is a CMOS-based 2-channel PWM Step-up (as Channel 1)/Step-down (as Channel 2) DC/DC converter controller. The R1282D002A consists of an oscillator, a PWM control circuit, a reference voltage unit, an error amplifier, a reference current unit, a protection circuit, and an under voltage lockout (UVLO) circuit. A high efficiency Step-up/Step-down DC/DC converter can be composed of this IC with inductors, diodes, power MOSFETs, resisters, and capacitors. Each output voltage and maximum duty cycle can be adjustable with external resistors, while soft-start time can be adjustable with external capacitors and resistors. As for a protection circuit, if Maximum duty cycle of either Step-up DC/DC converter side or Step-down DC/DC converter side is continued for a certain time, the R1280D002A latches both external drivers with their off state by its Latch-type protection circuit. Delay time for protection is internally fixed typically at 100ms. To release the protection circuit, restart with power-on (Voltage supplier is equal or less than UVLO detector threshold level). FEATURES • • • • • • Input Voltage Range .........................................2.5V to 5.5V Built-in Latch-type Protection Function by monitoring duty cycle (Fixed Delay Time Typ. 100ms) Oscillator Frequency .........................................700kHz High Accuracy Voltage Reference .................... ±1.5% U.V.L.O. Threshold............................................Typ. 2.2V (Hysteresis: Typ. 0.2V) Small Package ..................................................thin SON-10 (package thickness Max. 0.9mm) APPLICATIONS • Constant Voltage Power Source for Portable Equipment. • Constant Voltage Power Source for LCD and CCD. 1 R1282D002A BLOCK DIAGRAM DTC1 VFB1 OSC EXT1 AMPOUT1 CH1 Vref1 VIN GND Vrefout Vrefout UVLO VFB2 Vref2 EXT2 Latch Delay Circuit CH2 DTC2 SELECTION GUIDE The selection can be made with designating the part number as shown below; R1282D002A-TR ←Part Number ↑ a Code a Designation of Taping Type : (Refer to Taping Specifications.) Contents 2 R1282D002A PIN CONFIGURATION SON-10 10 9 8 7 6 (mark side) 12345 PIN DESCRIPTION Pin No 1 2 3 4 5 6 7 8 9 10 Symbol EXT1 GND AMPOUT1 DTC1 VFB1 VFB2 DTC2 Vrefout VIN EXT2 Ground Pin Amplifier Output Pin of Channel 1 Maximum Duty Cycle of Channel 1 Setting Pin Feedback pin of Channel 1 Feedback pin of Channel 2 Maximum Duty Cycle of Channel 2 Setting Pin Reference Output Pin Voltage Supply Pin of the IC External Transistor of Channel 2 Drive Pin (CMOS Output) Description External Transistor of Channel 1 Drive Pin (CMOS Output) ABSOLUTE MAXIMUM RATINGS Symbol VIN VEXT1,2 VAMPOUT1 VDTC1,2 Vrefout VFB1,2 IEXT1,2 PD Topt Tstg VIN Pin Voltage VEXT1,2 Pin Output Voltage AMPOUT1 Pin Voltage DTC1,2 Pin Voltage VREFOUT Pin Voltage VFB1,VFB2 Pin Voltage EXT1,2 Pin Output Current Power Dissipation Operating Temperature Range Storage Temperature Range Item Rating 6.5 −0.3~VIN+0.3 −0.3~VIN+0.3 −0.3~VIN+0.3 −0.3~VIN+0.3 −0.3~VIN+0.3 ±50 250 −40 to +85 −55 to +125 Unit V V V V V V mA mW °C °C 3 R1282D002A ELECTRICAL CHARACTERISTICS Topt=25°C Symbol VIN VREFOUT IROUT Item Operating Input Voltage VREFOUT Voltage Tolerance VREFOUT Output Current Conditions VIN=3.3V, IOUT=1mA VIN=3.3V 2.5V < VIN < 5.5V = = 1mA < IROUT < 10mA VIN=3.3V = = VIN=3.3V, VREFOUT=0V −40°C < = Min. 2.5 1.478 20 Typ. 1.500 2 6 25 ±150 Max. 5.5 1.522 6 12 Unit V V mA mV mV mA ppm/°C ∆VREFOUT/∆VIN VREFOUT Line Regulation ∆VREFOUT/∆IOUT VREFOUT Load Regulation ILIM VREFOUT Short Current Limit VREFOUT Voltage ∆VREFOUT/∆T Temperature Coefficient VFB1 VFB1 Voltage VFB1 Voltage ∆VFB1/∆T Temperature Coefficient VFB2 Voltage ∆VFB2/∆T Temperature Coefficient IVFB1,2 VFB1,2 Input Current fOSC IDD1 REXTH1 REXTL1 REXTH2 REXTL2 TDLY VUVLOD VUVLO VDTC10 VDTC1100 VDTC20 VDTC2100 AV1 FT1 VICR1 IAMPL IAMPH AV2 FT2 VICR2 VFB2 Oscillator Frequency Supply Current EXT1 "H" ON Resistance EXT1 "L" ON Resistance EXT2 "H" ON Resistance EXT2 "L" ON Resistance Delay Time for Protection UVLO Detector Threshold UVLO Released Voltage CH1 Duty=0% CH1 Duty=100% CH2 Duty=0% CH2 Duty=100% CH1 Open Loop Gain CH1 Single Gain Frequency Band CH1 Input Voltage Range CH1 Sink Current CH1 Source Current CH2 Open Loop Gain CH2 Single Gain Frequency Band CH2 Input Voltage Range CH2 Reference Voltage Topt < = 85 ° C 0.985 VIN=3.3V −40°C −40°C < = < = 1.000 ±150 ±150 1.015 V ppm/°C ppm/°C Topt Topt < = < = 85 ° C 85 ° C −0.1 VIN=5.5V,VFB1 or VFB2=0V or 5.5V EXT1,2 Pins at no load, VIN=3.3V VIN=5.5V, EXT1,2 pins at no load VIN=3.3V, IEXT=−20mA VIN=3.3V, IEXT=20mA VIN=3.3V, IEXT=−20mA VIN=3.3V, IEXT=20mA VIN=3.3V, VFB1=1.1V→0V 0.1 700 1.4 4.0 2.7 4.0 3.7 100 2.20 VUVLOD +0.20 0.2 1.2 0.2 1.2 110 1.9 0.7 to VIN 805 3.0 8.0 5.0 8.0 8.0 140 2.35 2.48 0.3 1.3 0.3 1.3 µA kHz mA Ω Ω Ω Ω ms V V V V V V dB MHz V µA 595 60 2.10 VIN=3.3V VIN=3.3V VIN=3.3V VIN=3.3V VIN=3.3V VIN=3.3V, AV1=0dB VIN=3.3V VIN=3.3V, VAMPOUT1=1.0V,VFB1=VFB1+ 0.1V VIN=3.3V, VAMPOUT1=1.0V,VFB1=VFB1− 0.1V VIN=3.3V VIN=3.3V, AV2=0dB VIN=3.3V VIN=3.3V 0.1 1.1 0.1 1.1 70 115 −1.4 −0.7 mA dB kHz V 60 600 −0.2 to VIN−1.3 1.000 0.985 1.015 V 4 R1282D002A Operation of Step-up DC/DC Converter and Output Current Step-up DC/DC Converter makes higher output voltage than input voltage by releasing the energy accumulated during on time of LX Transistor on input voltage. i2 Inductor VIN i1 GND Lx Tr CL Diode IOUT VOUT Discontinuous Mode IL ILxmax ILxmin ILxmin Tf Iconst t Ton T=1/fosc Toff Ton T=1/fosc Toff t IL Continuous Mode ILxmax Step 1. LX Tr. is on, then the current IL=i1 flows, and the energy is charged in L. In proportion to the on time of LX Tr. (Ton), IL=i1 increases from IL=ILXmin=0 and reaches ILXmax. Step 2. When the LX Tr. is off, L turns on Schottky Diode (SD), and IL=i2 flows to maintain IL=ILXmax. Step 3. IL=i2 gradually decreases, and after Tf passes, IL=ILXmin=0 is true, then SD turns off. Note that in the case of the continuous mode, before IL=ILXmin=0 is true, Toff passes, and the next cycle starts, then LX Tr. turns on again. In this case, ILXmin>0, therefore IL=ILXmin>0 is another starting point and ILX max increases. With the PWM controller, switching times during the time unit are fixed. By controlling Ton, output voltage is maintained. 5 R1282D002A Output Current and Selection of External Components Output Current of Step-up Circuit and External Components There are two modes, or discontinuous mode and continuous mode for the PWM step-up switching regulator depending on the continuous characteristic of inductor current. During on time of the transistor, when the voltage added on to the inductor is described as VIN, the current is VIN × t/L. Therefore, the electric power, PON, which is supplied with input side, can be described as in next formula. PON = ∫ Ton 0 VIN 2 × t/L dt ...................................................................................................Formula 1 With the step-up circuit, electric power is supplied from power source also during off time. In this case, input current is described as (VOUT−VIN)×t/L, therefore electric power, POFF is described as in next formula. POFF = ∫ Tf 0 VIN × (VOUT − VIN)t/L dt ...................................................................................Formula 2 In this formula, Tf means the time of which the energy saved in the inductance is being emitted. Thus average electric power, PAV is described as in the next formula. PAV = 1/(Ton + Toff) × { ∫ Ton 0 VIN2 × t/L dt + ∫ Tf 0 VIN × (VOUT − VIN)t/L dt} ............................Formula 3 In PWM control, when Tf=Toff is true, the inductor current becomes continuos, then the operation of switching regulator becomes continuous mode. In the continuous mode, the deviation of the current is equal between on time and off time. VIN×Ton/L=(VOUT−VIN)×Toff/L ..........................................................................................Formula 4 Further, the electric power, PAV is equal to output electric power, VOUT×IOUT, thus, IOUT = fOSC × VIN2×Ton2/{2×L ×(VOUT−VIN)}=VIN2×Ton/(2×L×VOUT)......................................Formula 5 When IOUT becomes more than VIN×Ton×Toff/(2×L×(Ton+Toff)), the current flows through the inductor, then the mode becomes continuous. The continuous current through the inductor is described as Iconst, then, IOUT = fOSC×VIN2 ×Ton2/(2×L×(VOUT−VIN))+VIN×Iconst/VOUT ...............................................Formula 6 6 R1282D002A In this moment, the peak current, ILXmax flowing through the inductor and the driver Tr. is described as follows: ILXmax = Iconst +VIN×Ton/L........................................................................................... Formula 7 With the formula 4,6, and ILXmax is, ILXmax = VOUT/VIN×IOUT+VIN×Ton/(2×L)........................................................................... Formula 8 Therefore, peak current is more than IOUT. Considering the value of ILXmax, the condition of input and output, and external components should be selected. In the formula 7, peak current ILXmax at discontinuous mode can be calculated. Put Iconst=0 in the formula. The explanation above is based on the ideal calculation, and the loss caused by LX switch and external components is not included. The actual maximum output current is between 50% and 80% of the calculation. Especially, when the ILX is large, or VIN is low, the loss of VIN is generated with the on resistance of the switch. As for VOUT, Vf (as much as 0.3V) of the diode should be considered. 7 R1282D002A Operation of Inverting DC/DC converter and Output Current The step-down DC/DC converter charges energy in the inductor when Lx transistor is ON, and discharges the energy from the inductor when Lx transistor is OFF and controls with less energy loss, so that a lower output voltage than the input voltage is obtained. The operation will be explained with reference to the following diagrams: IL Lx Tr i1 Inductor IOUT VOUT CL ILxmax VIN SD ILxmin topen t i2 Ton T=1/fosc Toff Step 1. Lx Tr. turns on and current IL (=i1) flows, and energy is charged into CL. At this moment, IL increases from ILmin. (=0) to reach ILmax. in proportion to the on-time period(ton) of LX Tr. Step 2. When Lx Tr. turns off, Schottky diode (SD) turns on in order that L maintains IL at ILmax, and current IL (=i2) flows. Step 3. IL decreases gradually and reaches ILmin. after a time period of topen, and SD turns off, provided that in the continuous mode, next cycle starts before IL becomes to 0 because toff time is not enough. In this case, IL value is from this ILmin (>0). In the case of PWM control system, the output voltage is maintained by controlling the on-time period (ton), with the oscillator frequency (fosc) being maintained constant. Discontinuous Conduction Mode and Continuous Conduction Mode The maximum value (ILmax) and the minimum value (ILmin) current which flow through the inductor is the same as those when Lx Tr. is ON and when it is OFF. The difference between ILmax and ILmin, which is represented by ∆I; ∆I = ILmax − ILmin = VOUT×topen / L = (VIN−VOUT) ×ton/L･･･Equation A wherein, T=1/fosc=ton+toff duty (%)=ton/T×100=ton× fosc ×100 topen < toff = In Equation A, VOUT×topen/L and (VIN−VOUT) ×ton/L are respectively shown the change of the current at ON, and the change of the current at OFF. When the output current (IOUT) is relatively small, topen < toff as illustrated in the above diagram. In this case, the energy is charged in the inductor during the time period of ton and is discharged in its entirely during the time period of toff, therefore ILmin becomes to zero (ILmin=0). When Iout is gradually increased, eventually, topen becomes to toff (topen=toff), and when IOUT is further increased, ILmin becomes larger than zero (ILmin>0). The former mode is referred to as the discontinuous mode and the latter mode is referred to as continuous mode. In the continuous mode, when Equation A is solved for ton and assumed that the solution is tonc, tonc=T×VOUT/VIN･･･ Equation B When ton