R1234D231B

R1234D SERIES PWM/VFM Step-Down DC/DC CONVERTER with Synchronous Rectifier NO.EA-137-070221 OUTLINE The R1234D Series are CMOS-based PWM step-down DC/DC Converters with synchronous rectifier, low supply current. 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 R1234D001C/D types, divider resistors are also necessary.) In terms of Output Voltage, it is fixed internally in the R1234Dxx1A/B types. While in the R1234D001C/D types, Output Voltage is adjustable with external divider resistors. PWM/VFM alternative circuit is active with Mode Pin of the R1234D 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. FEATURES • Supply Current ..................................................Typ. 230µA (R1234Dxx1A/C) Typ. 250µA (R1234Dxx1B/D) • Standby Current ................................................Typ. 0µA • Input Voltage Range ........................................ 2.4V to 5.5V (ABSOLUTE MAXIMUM : 6.5V) • Output Voltage Range.......................................2.2V to 3.3V (R1234Dxx1A/B) 0.8V to VIN (R1234Dxx1C/D) • Output Voltage Accuracy................................... ±2.0% (R1234DxxA/B) • Oscillator Frequency .........................................Typ. 500kHz (R1234Dxx1A/C) Typ. 800kHz (R1234Dxx1B/D) • Built-in Driver ON Resistance ...........................Pch 0.4Ω ,Nch 0.6Ω (VIN=3V) • Control mode switch .........................................MODE pin=”L”: PWN MODE pin=”H”: VFM • Efficiency...........................................................Typ. 90% • Package ............................................................SON-8 • Built-in Soft-start Function.................................Typ. 1.5ms • Latch-type Protection Function .........................Typ. 1.5ms • Built-in Current Limit Circuit APPLICATIONS • Power source for portable equipment. 1 R1234D BLOCK DIAGRAM R1234Dxx1A/B VDD MODE “L” PWM “H” VFM 3 VIN 6 1 OSC PWM/VFM CONTROL Phase Comp. 5 VOUT Lx 8 OUTPUT CONTROL Vref CE UVLO “H” Active Soft Start Chip Enable Current Protection 4 CE 2 PGND 7 AGND R1234Dxx1C/D VDD MODE 3 VIN 6 “L” PWM “H” VFM 1 OSC PWM/VFM CONTROL Phase Comp. 5 VFB Lx 8 OUTPUT CONTROL Vref Chip Enable “H” Active Current Limit 4 CE UVLO Soft Start 2 PGND 7 AGND 2 R1234D SELECTION GUIDE In the R1234D 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 with designating the part number as shown below; R1234Dxx1x-xx-x ←Part Number ↑ ↑ ↑↑ ↑ ↑ a b cd e f Code a b c Contents Designation of Package Type; D: SON-8 Setting Output Voltage (VOUT): Stepwise setting with a step of 0.1V in the range of 1.2V to 3.3V is possible for A/B version."00" is for Output Voltage Adjustable C/D version (0.8V to ) 1: fixed Designation of Optional Function A: 500kHz, Fixed Output Voltage B: 800kHz, Fixed Output Voltage C: 500kHz, Adjustable Output Voltage D: 800kHz, Adjustable Output Voltage Designation of Taping Type; (Refer to Taping Specification)"TR" is prescribed as a standard. Designation of Composition of pin plating -F: Lead free plating d e f 3 R1234D PIN CONFIGURATIO • Top View 8 7 65 SON-8 Bottom View 56 7 8 ∗ ∗ ∗ 1 2 34 43 2 1 PIN DESCRIPTION Pin No 1 2 3 4 5 6 7 8 Symbol VIN PGND VDD CE VOUT/VFB MODE AGND LX Voltage Supply Pin Power Ground Pin Voltage Supply Pin Chip Enable Pin (active with "H") Output/Feedback Pin Mode changer Pin ("L"=PWM, "H"=VFM) Analogue Ground Pin LX Pin (CMOS) Pin Description * Tab 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. ABSOLUTE MAXIMUM RATINGS Symbol VIN VDD VLX VCE VMODE VFB ILX PD Topt Tstg 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 (SON-8) Operating Temperature Range Storage Temperature Range Item Rating 6.5 6.5 −0.3 to VIN +0.3 −0.3 to VIN +0.3 −0.3 to VIN +0.3 −0.3 to VIN +0.3 −0.8 480 −40 to +85 −55 to +125 Unit V V V V V V A mW °C °C * ) For Power Dissipation, please refer to PACKAGE INFORMATION to be described. 4 R1234D ELECTRICAL CHARACTERISTICS • R1234DxxxA Topt=25°C Symbol VIN Item Operating Input Voltage Step-down Output Voltage Step-down Output Voltage Temperature Coefficient Oscillator Frequency Supply Current Standby Current ON Resistance of Pch Transistor ON Resistance of Nch Transistor LX Leakage Current VOUT Leakage Current CE Input Current MODE Pin Input Current CE "H" Input Voltage CE "L" Input Voltage MODE "H" Input Voltage MODE "L" Input Voltage Oscillator Maximum Duty Cycle Delay Time by Soft-Start function LX Limit Voltage Delay Time for protection circuit UVLO Threshold Voltage UVLO Released Voltage VFM Duty Cycle Conditions VIN=VCE=VSET+1.5V, VMODE=0V, IOUT=10mA −40°C < = Min. 2.4 Typ. Max. 5.5 Typ. Unit V VOUT ∆VOUT/∆Topt fosc IDD Istandby RONP RONN ILXleak IVOUTleak ICE IMODE VCEH VCEL VMODEH VMODEL Maxduty tstart VLXlim Tprot VUVLO1 VUVLO2 VFMduty Typ. ×0.98 VSET ±150 ×1.02 V ppm/ °C Topt < = 85 ° C 425 VIN=VCE=VSET+1.5V 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 or 5.5V VIN=5.5V, VCE=0V, VLX=0V or 5.5V VIN=5.5V, VMODE=0V, VCE=5.5V or 0V VIN=5.5V, VCE=0V, VMODE=5.5V or 0V VIN=5.5V, VOUT=0V VIN=2.4V, VOUT=0V VIN=VCE=5.5V, VOUT=0V VIN=VCE=2.4V, VOUT=0V VMODE=0V at no load, VIN=VCE=VSET+1.5V VMODE=VOUT=0V, VIN=VCE=3.0V VIN=VCE=VSET+1.5V, VMODE=0V VIN=VCE=2.5V→1.5V, VOUT =0V VIN=VCE=1.5V→2.5V, VOUT=0V VIN=VCE=VMODE=2.4V, VOUT=0V 500 230 0 575 300 5 0.9 0.9 5.0 0.1 0.1 0.1 kHz µA µA Ω Ω µA µA µA µA V 0.2 0.2 −5.0 −0.1 −0.1 −0.1 1.5 0.4 0.6 0.0 0.0 0.0 0.3 1.5 0.3 100 0.5 VIN −0.15 0.5 1.8 1.9 55 1.5 VIN −0.35 1.5 2.1 2.2 65 2.5 VIN −0.65 2.5 2.2 2.3 85 V V V % ms V ms V V % 5 R1234D • R1234DxxxB Topt=25°C Symbol VIN Item Operating Input Voltage Step-down Output Voltage Step-down Output Voltage Temperature Coefficient Oscillator Frequency Supply Current Standby Current ON Resistance of Pch Transistor ON Resistance of Nch Transistor LX Leakage Current VOUT Leakage Current CE Input Current MODE Pin Input Current CE "H" Input Voltage CE "L" Input Voltage MODE "H" Input Voltage MODE "L" Input Voltage Oscillator Maximum Duty Cycle Delay Time by Soft-Start function LX Limit Voltage Delay Time for protection circuit UVLO Threshold Voltage UVLO Released Voltage VFM Duty Cycle Conditions VIN=VCE=VSET+1.5V, VMODE=0V, IOUT=10mA −40°C < = Min. 2.4 Typ. Max. 5.5 Typ. Unit V VOUT ∆VOUT/∆Topt fosc IDD Istandby RONP RONN ILXleak IVOUTleak ICE IMODE VCEH VCEL VMODEH VMODEL Maxduty tstart VLXlim Tprot VUVLO1 VUVLO2 VFMduty Typ. ×0.98 VSET ±150 ×1.02 V ppm/ °C Topt < = 85 ° C 680 VIN=VCE=VSET+1.5V 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 or 5.5V VIN=5.5V, VCE=0V, VLX =0V or 5.5V VIN=5.5V, VMODE=0V, VCE=5.5V or 0V VIN=5.5V, VCE=0V, VMODE=5.5V or 0V VIN=5.5V, VOUT=0V VIN=2.4V, VOUT=0V VIN=VCE=5.5V, VOUT=0V VIN=VCE=2.4V, VOUT=0V VMODE=0V at no load, VIN=VCE=VSET+1.5V VMODE=VOUT=0V, VIN=VCE=3.0V VIN=VCE=VSET+1.5V, VMODE=0V VIN=VCE=2.5V→1.5V, VOUT =0V VIN=VCE=1.5V→2.5V, VOUT=0V VIN=VCE=VMODE=2.4V, VOUT=0V 800 250 0 920 450 5 0.9 0.9 5.0 0.1 0.1 0.1 kHz µA µA Ω Ω µA µA µA µA V 0.2 0.2 −5.0 −0.1 −0.1 −0.1 1.5 0.4 0.6 0.0 0.0 0.0 0.3 1.5 0.3 100 0.5 VIN −0.15 0.5 1.8 1.9 55 1.5 VIN −0.35 1.5 2.1 2.2 65 2.5 VIN −0.65 2.5 2.2 2.3 85 V V V % ms V ms V V % 6 R1234D • R1234DxxxC Topt=25°C Symbol VIN Item Operating Input Voltage Feedback Voltage Feedback Voltage Temperature Coefficient Oscillator Frequency Supply Current Standby Current ON Resistance of Pch Transistor ON Resistance of Nch Transistor LX Leakage Current VFB Leakage Current CE Input Current MODE Pin Input Current CE "H" Input Voltage CE "L" Input Voltage MODE "H" Input Voltage MODE "L" Input Voltage Oscillator Maximum Duty Cycle LX Limit Voltage Delay Time by Soft-Start function Delay Time for protection circuit UVLO Threshold Voltage UVLO Released Voltage VFM Duty Cycle Conditions VIN=VCE=VSET+1.5V, VMODE=0V, IOUT=10mA −40°C < = Min. 2.7 0.776 Typ. Max. 5.5 Unit V VFB ∆VFB/∆Topt fosc IDD Istandby RONP RONN ILXleak IVFBleak ICE IMODE VCEH VCEL VMODEH VMODEL Maxduty tstart VLXlim Tprot VUVLO1 VUVLO2 VFMduty 0.800 ±300 0.824 V ppm/ °C Topt < = 85 ° C 425 VIN=VCE=VSET+1.5V VIN=VCE=VSET+1.5V, VFB =VMODE=0V VIN=5.5V, VCE=VFB=0V VIN=5.0V VIN=5.0V VIN=5.5V, VCE=0V, VLX=0V or 5.5V VIN=5.5V, VCE=0V, VFB=0V or 5.5V VIN=5.5V, VMODE=0V, VCE=5.5V or 0V VIN=5.5V, VCE=0V, VMODE=5.5V or 0V VIN=5.5V, VFB=0V VIN=2.4V, VFB=0V VIN=VCE=5.5V, VFB=0V VIN=VCE=2.4V, VFB=0V VMODE=0V at no load, VIN=VCE=VSET+1.5V VMODE=VFB=0V, VIN=VCE=3.0V VIN=VCE=3.6V, VMODE=0V VIN=VCE=2.5V→1.5V, VMODE=0V VIN=VCE=1.5V→2.7V, VFB=0V VIN=VCE=VMODE=2.4V, VFB=0V 500 230 0 575 300 5 0.9 0.9 5.0 0.1 0.1 0.1 kHz µA µA Ω Ω µA µA µA µA V 0.2 0.2 −5.0 −0.1 −0.1 −0.1 1.5 0.4 0.6 0.0 0.0 0.0 0.3 1.5 0.3 100 0.5 VIN −0.15 0.5 1.95 2.20 55 1.5 VIN −0.35 1.5 2.20 2.40 65 2.5 VIN −0.65 2.5 2.45 2.65 85 V V V % ms V ms V V % 7 R1234D • R1234DxxxD Topt=25°C Symbol VIN Item Operating Input Voltage Feedback Voltage Feedback Voltage Temperature Coefficient Oscillator Frequency Supply Current Standby Current ON Resistance of Pch Transistor ON Resistance of Nch Transistor LX Leakage Current VFB Leakage Current CE Input Current MODE Pin Input Current CE "H" Input Voltage CE "L" Input Voltage MODE "H" Input Voltage MODE "L" Input Voltage Oscillator Maximum Duty Cycle LX Limit Voltage Delay Time by Soft-Start function Delay Time for protection circuit UVLO Threshold Voltage UVLO Released Voltage VFM Duty Cycle Conditions VIN=VCE=VSET+1.5V, VMODE=0V, IOUT=10mA −40°C < = Min. 2.7 0.776 Typ. Max. 5.5 Unit V VFB ∆VFB/∆Topt fosc IDD Istandby RONP RONN ILXleak IVFBleak ICE IMODE VCEH VCEL VMODEH VMODEL Maxduty tstart VLXlim Tprot VUVLO1 VUVLO2 VFMduty 0.800 ±300 0.824 V ppm/ °C Topt < = 85 ° C 680 VIN=VCE=VSET+1.5V VIN=VCE=VSET+1.5V, VFB=VMODE=0V VIN=5.5V, VCE=VFB=0V VIN=5.0V VIN=5.0V VIN=5.5V, VCE=0V, VLX=0V or 5.5V VIN=5.5V, VCE=0V, VFB=0V or 5.5V VIN=5.5V, VMODE=0V, VCE=5.5V or 0V VIN=5.5V, VCE=0V, VMODE=5.5V or 0V VIN=5.5V, VFB=0V VIN=2.4V, VFB=0V VIN=VCE=5.5V, VFB=0V VIN=VCE=2.4V, VFB=0V VMODE=0V at no load, VIN=VCE=VSET+1.5V VMODE=VFB=0V, VIN=VCE=3.0V VIN=VCE=3.6V, VMODE=0V VIN=VCE=2.5V→1.5V, VMODE=0V VIN=VCE=1.5V→2.7V, VFB=0V VIN=VCE=VMODE=2.4V, VFB=0V 800 250 0 920 400 5 0.9 0.9 5.0 0.1 0.1 0.1 kHz µA µA Ω Ω µA µA µA µA V 0.2 0.2 −5.0 −0.1 −0.1 −0.1 1.5 0.4 0.6 0.0 0.0 0.0 0.3 1.5 0.3 100 0.5 VIN −0.15 0.5 1.95 2.20 55 1.5 VIN −0.35 1.5 2.20 2.40 65 2.5 VIN −0.65 2.5 2.45 2.65 85 V V V % ms V ms V V % 8 R1234D TEST CIRCUITS 1 3 7 2 VIN VDD R1234D Series Lx CE 8 4 5 6 A 1 3 7 2 VIN VDD R1234D Series Lx CE 8 OSCILLOSCOPE 4 5 6 AGND VOUT AGND VOUT PGND MODE PGND MODE Test Circuit for Input Current and Leakage Current Test Circuit for Input Voltage and UVLO voltage OSCILLOSCOPE 1 3 7 2 VIN VDD R1234D Series Lx CE 8 4 5 6 VOUT L 10µF AGND VOUT PGND MODE Test Circuit for Output Voltage, Oscillator Frequency, Soft-Starting Time OSCILLOSCOPE 1 A VIN VDD R1234D Series Lx CE 8 4 5 6 1 3 7 2 VIN VDD R1234D Series Lx CE 8 4 5 6 A 3 7 2 AGND VOUT AGND VOUT PGND MODE PGND MODE 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 a ceramic capacitor 10µF. 9 R1234D TYPICAL APPLICATION AND TECHNICAL NOTES 1) Fixed Output Voltage Type L VOUT CIN 1 2 3 4 VIN PGND Lx AGND 8 7 6 5 LOAD COUT VDD CE MODE VOUT CIN COUT L 10µF C3216JB0J106M (TDK) 10µF ECSTOJX106R (Panasonic) 10µH LQH3C100K54 (Murata) 2) Adjustable Output Voltage Type L 1 CIN VIN Lx 8 7 6 5 Rb Cb VOUT 2 3 4 PGND VDD CE AGND MODE VOUT LOAD COUT R1 R2 CIN COUT L 10µF C3216JB0J106M (TDK) 10µF ECSTOJX106R (Panasonic) 10µH LQH3C100K54 (Murata) VFM mode may work with a parasitic diode, but we recommend that VFM mode used with an external diode in between LX and GND. As for PWM mode, an external diode is not necessary. As for how to choose Cb, Rb, R1, and R2 values, refer to the technical notes. 10 R1234D When you use these ICs, consider the following issues; • Input same voltage into the power supply pins, VIN and VDD. Set the same level as AGND and PGND. • When 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. • 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. • 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. • Use an external capacitor COUT with a capacity of 10µF or more, and with good high frequency characteristics such as tantalum capacitors. • At VFM mode, (MODE="H"), Latch protection circuit does not operate. • 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. 11 R1234D 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: IL ILmax ILmin topen i1 VIN Pch Tr Nch Tr L i2 CL GND VOUT ton T=1/fosc toff ⋅ Step 1: P-channel Tr. turns on and current IL (=i1) flows, and energy is charged into CL. At this moment, IL ⋅ Step 2: When P-channel Tr. turns off, Synchronous rectifier N-channel Tr. turns on in order that L maintains IL ⋅ Step 3: 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. at ILmax, and current IL (=i2) flows. increases from Ilmin (=0) to reach ILmax in proportion to the on-time period (ton) of P-channel Tr. • 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 Where, 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 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. 12 R1234D In the continuous mode, when Equation 1 is solved for ton and assumed that the solution is tonc tonc=t×VOUT/VIN............................................................................................................. Equation 2 When ton