R1224N122F

R1224N SERIES PWM/VFM step-down DC/DC Converter NO.EA-096-061102 OUTLINE The R1224N Series are CMOS-based PWM step-down DC/DC Converter controllers with low supply current. Each of these ICs consists of an oscillator, a PWM control circuit, a reference voltage unit, an error amplifier, a phase compensation circuit, a soft-start circuit, a protection circuit, a PWM/VFM alternative circuit, a chip enable circuit, resistors for output voltage detect, and input voltage detect circuit. A low ripple, high efficiency step-down DC/DC converter can be easily composed of this IC with only several external components, or a power-transistor, an inductor, a diode and capacitors. Output Voltage is fixed or can be adjusted with external resistors (Adjustable types are without PWM/VFM alternative circuit). With a PWM/VFM alternative circuit, when the load current is small, the operation is automatically switching into the VFM oscillator from PWM oscillator. Therefore, the efficiency at small load current is improved. Several types of the R1224Nxxx, which are without a PWM/VFM alternative circuit, are also available. If the term of maximum duty cycle keeps on a certain time, the embedded protection circuit works. The protection circuit is Reset-type protection circuit, and it works to restart the operation with soft-start and repeat this operation until maximum duty cycle condition is released. When the cause of large load current or something else is removed, the operation is automatically released and returns to normal operation. Further, built-in UVLO function works when the input voltage is equal or less than UVLO threshold, it makes this IC be standby and suppresses the consumption current and avoid an unstable operation. FEATURES • Supply Current ................................................................ Typ. 20µA (R1224Nxx2E/F/M/L, R1224N102M) Typ. 30µA (R1224Nxx2G, R1224N102G) Typ. 40µA (R1224Nxx2H, R1224N102H) • Standby Current .............................................................. Typ. 0µA • Input Voltage Range ....................................................... 2.3V~18.5V • Output Voltage Range ..................................................... 1.2V to 6.0V (R1224Nxx2x) 1.0V to VIN (R1224N102x) • Output Voltage Accuracy................................................. ±2.0% • Oscillator Frequency ....................................................... Typ. 180kHz (R1224Nxx2M, R1224N102M) Typ. 300kHz (R1224Nxx2E/G, R1224N102G) Typ. 500kHz (R1224Nxx2F/H, R1224N102H) • Efficiency ......................................................................... Typ. 90% • Low Temperature-Drift Coefficient of Output Voltage...... Typ. ±100ppm/°C • Package .......................................................................... SOT-23-5 • Built-in Soft-start Function ............................................... Typ. 10ms • Built-in Current Limit Circuit APPLICATIONS • Power source for hand-held communication equipment, cameras, video instruments such as VCRs, camcorders. • Power source for battery-powered equipment. • Power source for household electrical appliances. 1 R1224N BLOCK DIAGRAM *Fixed Output Voltage Type VIN 5 OSC 3 VOUT EXT 4 PW M/VFM CONTROL Amp Vref Soft Start Protection UVLO Chip Enable Vref 1 CE 2 GND *Adjustable Output Voltage Type VIN 5 OSC 3 VFB EXT 4 Amp Vref Soft Start Protection UVLO Chip Enable Vref 1 CE 2 GND 2 R1224N SELECTION GUIDE In the R1224N Series, the output voltage, the oscillator frequency, the optional function, 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; R1224Nxx2x-xx-x ←Part Number ↑ ↑ ↑↑ ↑ ↑ a b cd e f Code a b c Contents Designation of Package Type; N: SOT-23-5 Setting Output Voltage (VOUT): Stepwise setting with a step of 0.1V in the range of 1.2V to 6.0V is possible. Adjustable type; a=10 means Reference Voltage=1.0V Optional Function is G/H/M. 2: fixed Designation of Optional Function E : 300kHz, with a PWM/VFM alternative circuit F : 500kHz, with a PWM/VFM alternative circuit G : 300kHz, without a PWM/VFM alternative circuit H : 500kHz, without a PWM/VFM alternative circuit L : 180kHz, with a PWM/VFM alternative circuit M :180kHz, without a PWM/VFM alternative circuit 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 R1224N PIN CONFIGURATIO • 5 SOT-23-5 4 (mark side) 1 2 3 PIN DESCRIPTION Pin No 1 2 3 4 5 Symbol CE GND VOUT (VFB) EXT VIN Pin Description Chip Enable Pin (“H” Active) Ground Pin Pin for Monitoring Output Voltage (Feedback Voltage) External Transistor Drive Pin (CMOS Output) Power Supply Pin ABSOLUTE MAXIMUM RATINGS Symbol VIN VEXT VCE VOUT IEXT PD Topt Tstg VIN Supply Voltage EXT Pin Output Voltage CE Pin Input Voltage VOUT/VFB Pin Input Voltage EXT Pin Inductor Drive Output Current Power Dissipation (SOT-23-5)* Operating Temperature Range Storage Temperature Range Item Rating 20 −0.3 to VIN+0.3 −0.3 to VIN+0.3 −0.3 to VIN+0.3 ± 50 420 −40 to +85 −55 to +125 Unit V V V V A mW °C °C * ) For Power Dissipation, please refer to PACKAGE INFORMATION to be described. 4 R1224N ELECTRICAL CHARACTERISTICS • R1224Nxx2X (X=E/F/G/H/L/M) except R1224N102X Item Operating Input Voltage Step-down Output Voltage Step-down Output Voltage Temperature Coefficient VIN=VCE=VSET+1.5V, IOUT=−100mA When VSET < 1.5V, VIN=VCE=3.0V = −40°C < Topt < 85°C = = VIN=VCE=VSET+1.5V, IOUT=−100mA When VSET < 1.5, VIN=VCE=3.0V = L/M Version E/G Version F/H Version −40°C < Topt < 85°C = = VIN=VCE=VOUT=18.5V E/F/L/M Version G version H version VIN=18.5V, VCE=0V, VOUT=0V VIN=8V, VEXT=7.9V, VOUT=8V, VCE=8V VIN=8V, VEXT=0.1V, VOUT=0V, VCE=8V VIN=VCE=VOUT=18.5V VIN=VOUT=18.5V, VCE=0V VIN=8V, VOUT=0V VIN=8V, VOUT=0V 100 E/F/L Version VIN=VCE=2.5V to 1.5V, VOUT=0V VIN=VCE=1.5V to 2.5V, VOUT=0V VIN=VSET+1.5V, IOUT=−10mA VCE=0V→VSET+1.5V VIN=VCE=VSET+1.5V VOUT=VSET+1.5V→0V 5 5 1.8 35 2.0 VUVLO1 +0.1 10 15 2.2 2.3 20 30 −0.5 1.5 0.3 20 Conditions Min. 2.3 VSET ×0.98 VSET ±100 Typ. VIN VOUT ∆VOUT/ ∆Topt Topt=25°C Symbol Max. 18.5 VSET ×1.02 Unit V V ppm/°C fosc Oscillator Frequency 144 240 400 180 300 500 ±0.2 20 30 40 0.0 −17 30 0.0 0.0 216 360 600 kHz ∆fosc/ ∆Topt Oscillator Frequency Temperature Coefficient Supply Current 1 Standby Current EXT “H” Output Current EXT “L” Output Current CE “H” Input Current CE “L” Input Current CE “H” Input Voltage CE “L” Input Voltage Oscillator Maximum Duty Cycle VFM Duty Cycle UVLO Voltage UVLO Release Voltage Delay Time by Soft-Start function Delay Time for protection circuit %/°C 50 60 80 0.5 −10 IDD1 Istandby IEXTH IEXTL ICEH ICEL VCEH VCEL Maxdty VFMdty VUVLO1 VUVLO2 tstart tprot µA µA mA mA 0.5 µA µA V V % % V V ms ms 5 R1224N • R1224N102X (X=G/H/M) Item Operating Input Voltage Feedback Voltage Feedback Voltage Temperature Coefficient Oscillator Frequency Oscillator Frequency Temperature Coefficient Supply Current 1 Standby Current EXT “H” Output Current EXT “L” Output Current CE “H” Input Current CE “L” Input Current CE “H” Input Voltage CE “L” Input Voltage Oscillator Maximum Duty Cycle UVLO Voltage UVLO Release Voltage Delay Time by Soft-Start function Delay Time for protection circuit VIN=VCE=2.5V to 1.5V, VFB=0V VIN=VCE=1.5V to 2.5V, VFB=0V VIN=2.5V, IFB=−10mA VCE=0V→2.5V VIN=VCE=2.5V VFB=2.5V→0V 5 5 VIN=VCE=3.5V, IFB=−100mA −40°C < Topt < 85°C = = VIN=VCE=3.5V, IFB=−100mA M Version G Version H Version −40°C < Topt < 85°C = = VIN=VCE=VFB=18.5V M Version G Version H Version VIN=18.5V, VCE=0V, VFB=0V VIN=8V, VEXT=7.9V, VFB=8V, VCE=8V VIN=8V, VEXT=0.1V, VFB=0V, VCE=8V VIN=VCE=VFB=18.5V VIN=VFB=18.5V, VCE=0V VIN=8V, VFB=0V VIN=8V, VFB=0V 100 1.8 2.0 VUVLO1 +0.1 10 15 −0.5 1.5 20 144 240 400 Conditions Min. 2.3 0.98 1.00 ±100 180 300 500 ±0.2 20 30 40 0.0 −17 30 0.0 0.0 Typ. VIN VFB ∆VFB/ ∆Topt Topt=25°C Symbol Max. 18.5 1.02 Unit V V ppm/°C fosc ∆fosc/ ∆Topt 216 360 600 kHz %/°C 50 60 80 0.5 −10 IDD1 Istandby IEXTH IEXTL ICEH ICEL VCEH VCEL Maxdty VUVLO1 VUVLO2 tstart tprot µA µA mA mA 0.5 µA µA V 0.3 V % 2.2 2.3 20 30 V V ms ms 6 R1224N TYPICAL APPLICATION AND APPLICATION HINTS (1) Fixed Output Voltage Type (R1224Nxx2E/F/G/H/L/M except xx=10) L PMOS C1 R1 4 5 VIN EXT R1224N GND VOUT 3 C3 SD LOAD 1 CE C2 2 CE CONTROL PMOS: HAT1044M (Hitachi) SD1 : RB063L-30 (Rohm) C1 : 10µF (Ceramic Type) R1 : 10 Ω L : CR105-270MC (Sumida, 27µH) C3 : 47µF (Tantalum Type) C2 : 0.1µF (Ceramic Type) (2) Adjustable Output Type (R1224N102G/H/M) Example: Output Voltage=3.2V L PMOS C1 R1 C4 R4 R3 VFB 3 C3 SD R2 LOAD 4 5 VIN 1 CE EXT R1224N GND C2 2 CE CONTROL PMOS: HAT1044M (Hitachi) L : CR105-270MC (Sumida, 27µH) SD1 : RB063L-30 (Rohm) C3 : 47µF (Tantalum Type) C1 : 10µF (Ceramic Type) C2 : 0.1µF (Ceramic Type) C4: 1000pF (Ceramic Type) R1 : 10Ω, R2=22kΩ, R3=2.7kΩ, R4=33kΩ 7 R1224N When you use these ICs, consider the following issues; ⋅As shown in the block diagram, a parasitic diode is formed in each terminal, each of these diodes is not formed for load current, therefore do not use it in such a way. When you control the CE pin by another power supply, do not make its “H” level more than the voltage level of VIN pin. ⋅Set external components as close as possible to the IC and minimize the connection between the components and the IC. In particular, a capacitor should be connected to VOUT pin with the minimum connection. Make sufficient ground and reinforce supplying. A large switching current could flow through the connection of power supply, an inductor and the connection of VOUT. If the impedance of the connection of power supply is high, the voltage level of power supply of the IC fluctuates with the switching current. This may cause unstable operation of the IC. ⋅Protection circuit may work if the maximum duty cycle continue for the time defined in the electrical characteristics. Once after stopping the output voltage, output will restart with soft-start operation. If the difference between input voltage and output voltage is small, the protection circuit may work. ⋅Use capacitors with a capacity of 22µF or more for VOUT pin, and with good high frequency characteristics such as tantalum capacitors. We recommend you to use output capacitors with an allowable voltage at least twice as much as setting output voltage. This is because there may be a case where a spike-shaped high voltage is generated by an inductor when an external transistor is on and off. ⋅Choose an inductor that has sufficiently small D.C. resistance and large allowable current and is hard to reach magnetic saturation. And if the value of inductance of an inductor is extremely small, the ILX may exceed the absolute maximum rating at the maximum loading. Use an inductor with appropriate inductance. ⋅Use a diode of a Schottky type with high switching speed, and also pay attention to its current capacity. ⋅Do not use this IC under the condition with VIN voltage at equal or less than minimum operating voltage. ⋅When the threshold level of an external power MOSFET is rather low and the drive-ability of voltage supplier is small, if the output pin is short circuit, input voltage may be equal or less than UVLO detector threshold. In this case, the devise is reset with UVLO function that is different from the reset-protection function caused by maximum duty cycle. ⋅With the PWM/VFM alternative circuit, when the on duty cycle of switching is 35% or less, the R1224N alters from PWM mode to VFM mode (Pulse skip mode). The purpose of this circuit is raising the efficiency with a light load by skipping the frequency and suppressing the consumption current. However, the ratio of output voltage against input voltage is 35% or less, (ex. VIN>8.6V and VOUT=3.0V) even if the large current may be loaded, the IC keeps its VFM mode. As a result, frequency might be decreased, and oscillation waveform might be unstable. These phenomena are the typical characteristics of the IC with PWM/VFM alternative circuit. 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. 8 R1224N How to Adjust Output Voltage and about Phase Compensation As for Adjustable Output type, feedback pin (VFB) voltage is controlled to maintain 1.0V. Output Voltage, VOUT is as following equation: VOUT: R2+R4=VFB: R2 VOUT=VFB×(R2+R4)/R2 Thus, with changing the value of R2 and R4, output voltage can be set in the specified range. In the DC/DC converter, with the load current and external components such as L and C, phase might be behind 180 degree. In this case, the phase margin of the system will be less and stability will be worse. To prevent this, phase margin should be secured with proceeding the phase. A pole is formed with external components L and C3. Fpole ~ 1/2π L × C3 A zero (signal back to zero) is formed with R4 and C4. ≅Fzero~1/(2π×R4×C4) For example, if L=27µH, C3=47µF, the cut off frequency of the pole is approximately 4.5kHz. To make the cut off frequency of the pole as much as 4.5kHz, set R4=33kΩ and C4=1000pF. If VOUT is set at 2.5V, R2=22kΩ is appropriate. R3 prevents feedback of the noise to VFB pin, about 2.7kΩ is appropriate value. L PMOS C1 R1 C4 R4 R3 VFB 3 C3 SD R2 LOAD 4 5 VIN 1 CE EXT R1224N GND C2 2 CE CONTROL 9 R1224N 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 Lx Tr SD GND L i2 CL VOUT IL ILmin ILmax topen 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 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 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, topen0). The former mode is referred to as the discontinuous mode and the latter mode is referred to as continuous mode. 10 R1224N 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