R1230D251C-TL

2001. Sep. 8 PWM/VFM step-down DC/DC converter with Synchronous Rectifier R1230D Series s OUTLINE The R1230D Series are PWM step-down DC/DC Converters with synchronous rectifier, low supply current by CMOS process. Each of these ICs consists of an oscillator, a PWM control circuit, a reference voltage unit, an error amplifier, a soft-start circuit, protection circuits, a protection against miss operation under low voltage (UVLO), PWM/VFM alternative circuit, a chip enable circuit, and a driver transistor. A low ripple, high efficiency step-down DC/DC converter can be easily composed of this IC with only a few kinds of external components, or an inductor and capacitors. (As for R1230D001C/D types, divider resistors are also necessary.) In terms of Output Voltage, it is fixed internally in the R1230DXX1A/B types. While in the R1230D001C/D types, Output Voltage is adjustable with external divider resistors. PWM/VFM alternative circuit is active with Mode Pin of the R1230D Series. Thus, when the load current is small, the operation can be switching into the VFM operation from PWM operation by the logic of MODE pin and the efficiency at small load current can be improved. As protection circuits, Current Limit circuit which limits peak current of Lx at each clock cycle, and Latch type protection circuit which works if the term of Over-current condition keeps on a certain time in PWM mode exist. Latch-type protection circuit works to latch an internal driver with keeping it disable. To release the condition of protection, after disable this IC with a chip enable circuit, enable it again, or restart this IC with power-on or make the supply voltage at UVLO detector threshold level or lower than UVLO. s FEATURES q Built-in Driver ON Resistance • • • • • • • • • • • • • P-channel 0.35Ω, N-channel 0.45Ω (at VIN=3V) q Built-in Soft-start Function (TYP. 1.5ms), and Latch-type Protection Function (Delay Time; TYP. 1.5ms) q Two choices of Oscillator Frequency • • • • • • 500kHz, 800kHz q PWM/VFM alternative with MODE pin • • • • • • PWM operation; MODE pin at “L”, VFM operation; MODE pin at “H” q High Efficiency • • • • • • • • • • • • • • • • • • TYP. 90% q Output Voltage • • • • • • • • •Stepwise Setting with a step of 0.1V in the range of 1.2V ∼ 4.0V(XX1A/B Type) or adjustable in the range of 0.8V to VIN(001C/D Type) q High Accuracy Output Voltage • • • • • • • • • •±2.0%(XX1A/B Type) q Package • • • • • SON8 (Max height 0.9mm, thin type) s APPLICATIONS q Power source for portable equipment. Rev. 1.12 -1- s BLOCK DIAGRAM qR1230DXX1A/B VDD VIN MODE “L”= PWM “H”= VFM OSC VOUT Lx PWM/VFM CONTROL OUTPUT CONTROL Phase Compensation Vref CE UVLO “H” Active Soft Start Chip Enable Current Protection CE PGND qR1230D001C/D AGND VDD MODE “L”= PWM “H”= VFM VIN OSC VFB Lx PWM/VFM CONTROL OUTPUT CONTROL Phase Compensation “H” Active Vref Chip Enable CE Current Protection UVLO Soft Start PGND AGND Rev. 1.12 -2- s SELECTION GUIDE In the R1230D Series, the output voltage, the oscillator frequency, and the taping type for the ICs can be selected at the user’s request. The selection can be made by designating the part number as shown below; R1230DXXXX-XX ↑ ↑↑ ↑ a bc d Code a Contents Setting Output Voltage(VOUT): Stepwise setting with a step of 0.1V in the range of 1.2V to 4.0V is possible for A/B version. “00” is for Output Voltage Adjustable C/D version 1 : fixed Designation of Optional Function A : 500kHz, Fixed Output Voltage B : 800 kHz, Fixed Output Voltage C : 500kHz, Adjustable Output Voltage D : 800kHz, Adjustable Output Voltage Designation of Taping Type; Ex. :TR,TL(refer to Taping Specification) ”TR” is prescribed as a standard. b c d s PIN CONFIGURATION q SON-8 2.9±0.2 0.48TYP 8 5 (0.2) 2.8±0.2 3.0±0.2 * * 1 0.13±0.05 4 0.9 MAX. *Attention : Tab suspension leads in the parts have GND level. (They are connected to the reverse side of this IC.) Do not connect to other wires or land patterns. 0.65 0.3±0.1 0.1 0.1 M Unit : mm Rev. 1.12 -3- (0.2) s PIN DESCRIPTION Pin No. 1 2 3 4 5 6 7 8 Symbol VIN PGND VDD CE VOUT/VFB MODE AGND Lx Description Voltage Supply Pin Ground Pin Voltage Supply Pin Chip Enable Pin (active with “H”) Output/Feedback Pin Mode changer Pin (PWM mode at “L”, VFM mode at “H”.) Ground Pin Lx Pin s ABSOLUTE MAXIMUM RATINGS Symbol VIN VDD VLX VCE VMODE VFB ILX PD Topt Tstg Item VIN Supply Voltage VDD Pin Voltage Lx Pin Voltage CE Pin Input Voltage MODE Pin Input Voltage VFB Pin Input Voltage LX Pin Output Current Power Dissipation Operating Temperature Range Storage Temperature Range (AGND=PGND=0V) Rating Unit 6.5 V 6.5 V V -0.3∼VIN+0.3 V -0.3∼VIN+0.3 V -0.3∼VIN+0.3 V -0.3∼VIN+0.3 -0.8 A 250 mW °C -40∼+85 °C -55∼+125 Rev. 1.12 -4- s ELECTRICAL CHARACTERISTICS qR1230D**1A/B Symbol Item VIN Operating Input Voltage VOUT Step-down Output Voltage ∆VOUT/ ∆T fosc fosc IDD IDD Istb RONP Step-down Output Voltage Temperature Coefficient Oscillator Frequency(xx1A) Oscillator Frequency(xx1B) Supply Current(xx1A) Supply Current(xx1B) Conditions VIN=VCE=VSET+1.5V, VMODE=0V, IOUT=10mA -40°C ≤ Topt ≤ 85°C VIN=VCE=VSET+1.5V VIN=VCE=VSET+1.5V VIN=VCE=VSET+1.5V, VOUT=VMODE=0V VIN=VCE=VSET+1.5V, VOUT=VMODE=0V VIN=5.5V, VCE=VOUT=0V VIN=5.0V VIN=5.0V VIN=5.5V, VCE=0V, VLX=0V/5.5V VIN=5.5V, VCE=0V, VLX=0V/5.5V VIN=5.5V, VMODE=0V, VCE=5.5V/0V VIN=5.5V, VOUT=0V VIN=2.4V, VOUT=0V VMODE=0V VMODE= VOUT=0V, VIN=VCE=3.0V MIN. 2.4 TYP.× 0.980 (Topt=25°C) MAX. Unit 5.5 V VSET TYP.× V 1.020 ppm ±150 /°C 500 575 kHz 800 920 kHz 230 300 µA TYP. 250 0 0.35 0.45 0.0 0.0 0.0 350 5 0.60 0.70 0.1 0.1 0.1 µA µA Ω Ω µA µA µA V V % V ms ms V V µA V V % 425 680 Standby Current ON Resistance of Pch Transistor RONN ON Resistance of Nch Transistor ILXleak Lx Leakage Current IVOUT VOUT Leakage Current ICE CE Input Current VCEH CE "H" Input Voltage VCEL CE "L" Input Voltage Maxdty Oscillator Maximum Duty Cycle VLX Lx Limit Voltage Tstart Tprot VUVLO1 VUVLO2 IMODE VMODEH VMODEL VFMdty 0.20 0.20 -0.1 -0.1 -0.1 1.5 Delay Time by Soft-Start function at no load, VIN=VCE=VSET+1.5V Delay Time for protection circuit VIN=VCE=VSET+1.5V, VMODE=0V UVLO Threshold Voltage UVLO Released Voltage MODE Pin Input Current MODE ”H” Input Voltage MODE ”L” Input Voltage VFM Duty Cycle VIN=VCE=2.5V->1.5V, VOUT=0V VIN=VCE=1.5V->2.5V, VOUT=0V VIN=5.5V, VCE=0V, VMODE=5.5V/0V VIN=VCE=5.5V, VOUT=0V VIN=VCE=2.4V, VOUT=0V VIN=VCE= VMODE=2.4V, VOUT=0V 0.3 100 VIN-0.15 VIN-0.35 VIN0.55 0.5 1.5 2.5 0.5 1.5 2.5 1.8 2.1 2.2 1.9 2.2 2.3 -0.1 0.1 1.5 0.3 55 65 85 Rev. 1.12 -5- qR1230D001C/D Symbol Item VIN Operating Input Voltage VFB Feedback Voltage Feedback Voltage Temperature Coefficient Oscillator Frequency(xx1C) Oscillator Frequency(xx1D) Supply Current(xx1C) Supply Current(xx1D) Standby Current ON Resistance of Pch Transistor RONN ON Resistance of Nch Transistor ILXleak Lx Leakage Current IVFB VFB Leakage Current ICE CE Input Current VCEH CE "H" Input Voltage VCEL CE "L" Input Voltage Maxdty Oscillator Maximum Duty Cycle VLX Lx Limit Voltage Tstart Tprot VUVLO1 VUVLO2 IMODE VMODE VMODEL VFMdty ∆VFB/ ∆T fosc fosc IDD IDD Istb RONP Conditions VIN=VCE=VSET+1.5V, VMODE=0V, IOUT=10mA -40°C ≤ Topt ≤ 85°C VIN=VCE=VSET+1.5V VIN=VCE=VSET+1.5V VIN=VCE=5.5V, VFB=VMODE=0V VIN=VCE=5.5V, VFB=VMODE=0V VIN=5.5V, VCE=VFB=0V VIN=5.0V VIN=5.0V VIN=5.5V, VCE=0V, VLX=0V/5.5V VIN=5.5V, VCE=0V, VFB=0V/5.5V VIN=5.5V, VMODE=0V, VCE=5.5V/0V VIN=5.5V, VFB=0V VIN=2.4V, VFB=0V VMODE=0V VIN=VCE=3.0V, VMODE=0V, VFB=0V MIN. 2.4 0.776 TYP. 0.800 ±150 (Topt=25°C) MAX. Unit 5.5 V 0.824 V ppm /°C 575 kHz 920 kHz 300 µA 350 µA 5 µA 0.60 Ω 0.70 0.1 0.1 0.1 0.3 Ω µA µA µA V V % V ms ms V V µA V V % 425 680 0.20 0.20 -0.1 -0.1 -0.1 1.5 100 VIN-0.15 0.5 1.8 1.9 -0.1 1.5 55 500 800 230 250 0 0.35 0.45 0.0 0.0 0.0 Delay Time by Soft-Start function at no load, VIN=VCE=VSET+1.5V Delay Time for protection circuit VIN=VCE=3.6V, VMODE=0V UVLO Threshold Voltage UVLO Released Voltage MODE Pin Input Current MODE ”H” Input Voltage MODE ”L” Input Voltage VFM Duty Cycle VIN=VCE=2.5V->1.5V, VFB=0V VIN=VCE=1.5V->2.5V, VFB=0V VIN=5.5V, VMODE=5.5V/0V, VCE=0V VIN=VCE=5.5V, VFB=0V VIN=VCE=2.4V, VFB=0V VIN=VCE=VMODE=2.4V, VFB=0V VIN0.35 1.5 1.5 2.1 2.2 VIN0.55 2.5 2.2 2.3 0.1 0.3 85 65 Rev. 1.12 -6- s TEST CIRCUITS VIN VDD CE AGND VOUT Lx VIN VDD Lx CE VOUT OSCILLOSCOPE A PGND MODE AGND PGND MODE Test Circuit for Input Current and Leakage Current Test Circuit for Input Voltage and UVLO voltage OSCILLOSCOPE VIN VDD Lx CE V AGND OUT V OUT L 10uF PGND MODE Test Circuit for Output Voltage, Oscillator Frequency, Soft-Starting Time VIN Lx CE OSCILLOSCOPE V IN A VDD Lx CE AGND VOUT VDD A PGND MODE AGND PGND MODE VOUT Test Circuit for Supply Current and Standby Current Test Circuit for ON resistance of Lx, Limit Voltage, Delay Time of Protection Circuit The bypass capacitor between Power Supply and GND is Ceramic capacitor 10µF. Rev. 1.12 -7- s TYPICAL APPLICATION AND TECHNICAL NOTES 1) Fixed Output Voltage Type VOUT VIN CIN PGND VDD CE Lx AGND MODE VOUT COUT L LOAD L : 10µH LQH3C100K54(Murata) COUT : 10µF ECSTOJX106R(Panasonic) CIN : 10µF C3216JB0J106M(TDK) 2) Adjustable Output Voltage Type L VIN CIN PGND VDD CE LX AGND MODE VFB Rb 10µH LQH3C100K54 (Murata) 10µF ECSTOJX106R (Panasonic) 10µF C3216JB0J106M (TDK) VOUT Cb R1 COUT R2 LOAD L: COUT: CIN: Standard value of the sum of Divider Resistors, R1+R2 is as much as 100kΩ. Cb value for phase compensation depends on values of L, C, and R1. Refer to the technical notes. If a ceramic capacitor is used as an output capacitor, add 0.2Ω or more resistance to compensate the ESR of the capacitor. When you use these ICs, consider the following issues; q Input same voltage into Power Supply pins, VIN and VDD. Set the same level as AGND and PGND. q W hen you control the CE pin and MODE pin by another power supply, do not make its "H" level more than the voltage level of VIN / VDD pin. q Set external components such as an inductor, CIN, COUT as close as possible to the IC, in particular, minimize the wiring to VIN pin and PGND pin. q At stand by mode, (CE=”L”), the Lx output is Hi-Z, or both P-channel transistor and N-channel transistor of Lx pin turn off. q Use an external capacitor COUT with a capacity of 10µF or more, and with good high frequency characteristics such as tantalum capacitors. q At VFM mode, (MODE=”H”), Latch protection circuit does not operate. Rev. 1.12 -8- q q If the mode is switched over into PWM mode from VFM mode during the operation, change the mode at light load current. If the load current us large, output voltage may decline. Reinforce the VIN, PGND, and VOUT lines sufficiently. Large switching current may flow in these lines. If the impedance of VIN and PGND lines is too large, the internal voltage level in this IC may shift caused by the switching current, and the operation might be unstable. ✰ The performance of power source circuits using these ICs extremely depends upon the peripheral circuits. Pay attention in the selection of the peripheral circuits. In particular, design the peripheral circuits in a way that the values such as voltage, current, and power of each component, PCB patterns and the IC do not exceed their respected rated values. s OPERATION of step-down 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: i1 IOUT VIN Pch Tr Nch Tr L i2 CL VOUT ILmax ILmin topen ton T=1/fosc toff Step 1: Step 2: Step 3: P-channel 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 P-channel Tr. When P-channel Tr. turns off, Synchronous rectifier N-channel Tr. turns on in order that L maintains IL at ILmax, and current IL (=i2) flows. IL (=i2) decreases gradually and reaches IL=ILmin=0 after a time period of topen, and N-channel Tr. 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 increases 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. q Discontinuous Conduction Mode and Continuous Conduction Mode The maximum value (ILmax) and the minimum value (ILmin) of the current flowing through the inductor are the same as those when P-channel Tr. turns on and off. The difference between ILmax and ILmin, which is represented by ∆I; ∆I = ILmax – ILmin = VOUT × topen / L = (VIN-VOUT)×ton/L⋅⋅⋅Equation 1 Wherein T=1/fosc=ton+toff duty (%)=ton/T×100=ton×fosc×100 topen ≤ toff In Equation 1, VOUT×topen/L and (VIN-VOUT)×ton/L respectively show the change of the current at “ON”, and the change of the current at “OFF”. When the output current (IOUT) is relatively small, topen0). 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 1 is solved for ton and assumed that the solution is tonc, Rev. 1.12 -9- tonc =T×VIN/VOUT⋅⋅⋅ Equation 2 When ton