CE8501 CHIPOWER | Alldatasheet
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V0.1 1(12) CE8501①②③④ INTRODUCTION: FEATURES: The CE8501 is a 1.5MHz constant frequency, slope compensated current mode PWM synchronous step-down converter. It is ideal for powering portable equipment which runs from a single cell Lithium-Ion battery. 100% duty cycle provides low dropout operation, extending battery life in portable systems. In power saving mode, 40 μA quiescent current is very suitable for DSP/MCU in standby operation; and in active mode, low output ripple voltage is good enough for noise sensitive applications. The two modes can be automatically switched according to the load current. z High efficiency : Up to 96% z Output Current: 600mA (Typ.) z 1.5MHz Constant Switching Frequency z No Schottky Diode Required z Input Voltage: 1.8V to 5.5V z 0.6V Reference Allows Low Output Voltage z Low Dropout: 100% duty Cycle z Low Quiescent Current: 40 μA z Shutdown Current: <1 μA z Current Mode Operation for Excellent Line and Load Transient Response z Built-in Thermal Protection z Package: SOT-23-5 APPLICATIONS： z Cellular and Smart Phones z Personal Information Appliances z Wireless and DSL Modems z Digital Still and Video Cameras z Microprocessors Core Supplies z Portable consumer equipments PIN CONFIGURATION: ORDER INFORMATION: DESIGNATOR SYMBOL DESCRIPTION ① A Standard ②③ Integer Output Voltage e.g.1.8V=②:1, ③:8 Adj=②:, ③: ④ M/MR Package：SOT-23-5 1.5MHz 600mA Synchronous Step-Down Converter with Low Quiescent Current CE8501 Series
V0.1 2(12) 1.5MHz 600mA Synchronous Step-Down Converter with Low Quiescent Current CE8501 Series Tabel1. Pin Description PIN NUMBER PIN NAME FUNCTION M MR 1 3 CE Chip Enable Pin 2 2 V SS Ground 3 5 SW External Inductor Connection Pin 4 1 V IN Power Input 5 4 V OUT/FB Output Pin/Feedback(ADJ Version) BLOCK DIAGRAM ABSOLUTE MAXIMUM RATINGS PARAMETER SYMBOL RATINGS UNITS Input Voltage V IN V SS-0.3~VSS+6.5 V CE,SW,FB/VOUT Voltage V SS-0.3~VIN+0.3 V Peak SW Sink and Source Current ISWMAX 1500 mA Power Dissipation SOT-23-5 Pd 400 mW Operating Temperature T opr -40~+85 ℃ Junction Temperature T j 125 ℃ Storage Temperature T stg -40~+125 ℃ Soldering Temperature & Time T solder 260℃, 10s
V0.1 3(12) 1.5MHz 600mA Synchronous Step-Down Converter with Low Quiescent Current CE8501 Series ELECTRICAL CHARACTERISTICS CE8501 Series (V IN=CE=3.6V, Ta=25℃, Test Circuit Figure1, unless otherwise specified) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Output Voltage V OUT(F) (1) IOUT =100mA V OUT×0.97 V OUT V OUT×1.03 V Feedback Voltage V FB TA=25℃ 0.5880 0.600 0.6120 V 0℃≤TA≤85℃ 0.5865 0.600 0.6135 Input Voltage V IN 1.8 5.5 V Supply Current1 （Active MODE） ISS1 V FB=0.50V 270 400 μA Supply Current2 （Power Saving Mode） ISS2 V FB=0.63V 40 50 μA Shutdown Current I SHDN V CE=VSS 0.1 1.0 μA Feedback Current I FB V FB=0.65V ±30 nA Maximum Output Current I OUT － 600 mA VFB Line Regulation ∆VFB VIN= 1.8V~5.5V 0.40 %/V Output Voltage Line Regulation ∆VOUT VIN= 1.8V~5.5V IOUT=10mA 0.40 %/V Output Voltage Load Regulation ∆VLOAD IOUT =1mA ~600mA 0.02 %/mA Oscillator Frequency f osc VFB=0.6V or VOUT=100% 1.2 1.5 1.8 MHz Peak Inductor Current I PK VIN=3V,VFB=0.5V or V OUT=90% 1.0 A RDS(ON) OF P-CH FET R PFET I SW = 100mA 0.45 0.60 Ω RDS(ON) OF N-CH FET R NFET I SW = -100mA 0.35 0.50 Ω SW Leakage I LSW CE=0,VSW=0 or 5V, VIN=5V ±0.01 ±1 μA CE "High" Voltage(2) VCE“H” 1.5 V IN V CE "Low" Voltage(3) VCE“L” 0.3 V CE Leakage Current I CE ±0.1 ±1 μA NOTE : 1. VOUT(F):The fixed voltage version effective output voltage. 2. High Voltage：Forcing CE above 1.5V enables the part. 3. Low Voltage：Forcing CE below 0.3V shuts down the device.
V0.1 4(12) 1.5MHz 600mA Synchronous Step-Down Converter with Low Quiescent Current CE8501 Series TYPICAL APPLICATION CIRCUITS 4.7μF 2.2μH 10μF VOUT 1.8V OFF ON VSS CE VOUT SWVIN VIN Figure1 Basic Application Circuit TYPICAL PERFORMANCE CHARACTERISTICS (Test Figure1 above unless otherwise specified)
V0.1 1.5MHz 6 600mA Synch hronous Step p-Down Conv 5(12) verters with L Low Quiescen nt Current CE8501 Series
V0.1 1.5MHz 6 600mA Synch hronous Step p-Down Conv 6(12) verters with L Low Quiescen nt Current CE8501 Series
V0.1 7(12) 1.5MHz 600mA Synchronous Step-Down Converters with Low Quiescent Current CE8501 Series OPERATION MAIN CONTROL LOOP The CE8501 uses a constant frequency, current mode step-down architecture. Both the main (P-channel MOSFET) and synchronous (N-channel MOSFET) switches are internal. During normal operation, the internal top power MOSFET is turned on each cycle when the oscillator sets the RS la tch, and turned off when the current comparator, I COMP, resets the RS latch. The peak inductor current at which I COMP resets the RS latch, is controll ed by the output of error amplifier EA. When the load current increases, it causes a slight decrease in the feedback voltage, FB, relative to the 0.6V reference, which in turn, causes the EA amplifier’s output voltage to increase until the average inductor current matches the new load current. While the top MOSFET is off, the bottom MOSFET is turned on until either the inductor curr ent starts to reverse, as indicated by the curr ent reversal comparator I RCMP, or the beginning of the next clock cycle. MAXIMUM LOAD CURRENT The CE8501 will operate with input voltage as low as 1.8V, however, the maximum load current decreases at lower input due to large IR drop on the main switch and synchronous rectifier. The slope compensation signal reduces the peak inductor current as a func tion of the duty cycle to prevent sub-harmonic osc illations at duty cycles greater than 50%.Conversely the current limit increase as the duty cycle decreases. DISCONTINUOUS MODE OPERATION At light loads, the inductor current may reach zero reverse on each pulse. The bottom MOSFET is turned off by the curr ent reversal comparator, I RCMP, and the switch voltage will ring. This is discontinuous mode operat ion, and is normal behavior for the switching regulator. At very light loads, the CE8501 will automatically skip pulses in discontinuous mode operati on to maintain output regulation. SLOPE COMPENSATION Slope compensation provides stability in constant frequency archit ecture by preventing sub-harmonic oscillations at high duty cycles. It is accomplished internally by adding a compensating ramp to t he inductor current signal at duty cycles in excess of 50%. This slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for excellent load and line response. POWER SAVING MODE OPERATION At very light loads, the chip automatically enters power saving mode. In power saving mode at light load, a control circuit puts most of the circuit into sleep in order to reduce quiescent current and improve efficiency at light load. When the output voltage drops to certain threshold, the control circuit turns ba ck on the oscillator and the PWM control loop, boosting output backup. When an upper threshold is reac hed, the control circuit again puts most of circuit into sleep, reducing quiescent current. During power saving mode operation, the converte r positions the output voltage slightly higher than the nominal output voltage during PWM operation, allowing additional headroom for voltage drop during a load transient from light to heavy load. While the power saving mode improves light load efficiency, however, with the turning on and off, the noise or ripple voltage is
V0.1 8(12) 1.5MHz 600mA Synchronous Step-Down Converters with Low Quiescent Current CE8501 Series larger than that in the active Mode. DROPOUT OPERATION As the input supply vo ltage decreases to a value approaching the out put voltage, the duty cycle increases toward the maximum on-time. Further reduction of the supply voltage forces the main switch to remain on for more than one cycle until reaches 100% duty cycle. The output voltage will then be determined by the input voltage minus the voltage drop across the P-channel MOSFET and the inductor. An important detail to remember is that at low inputs supply voltages, the R DS(ON) of the P-channel switch increases . Therefore, the user should calculate the powe r dissipation when the CE8501 is used at 100% duty cycle with low input voltage. APPLICATION INFORMATION The basic CE8501 applic ation circuits are shown in Figure 1.External component selection is driven by the load requirement and begins with the selection of L followed by CIN and COUT. SETTING THE OUTPUT VOLTAGE Figure1 shows the basic application circuit with CE8501 adjustable output version. The external resistor sets the output voltage according to the following equation: VOUT ൌ 0.6V ൈ ൬1 R2 R1൰ Table 2.Resistor select for output voltage setting VOUT R1 R2 1.2V 316K 316K 1.5V 316K 470K 1.8V 316K 634K 2.5V 316K 1M INPUT CAPACITOR SELECTION In continuous mode, the source current of the top MOSFET is a square wave of duty cycle V OUT/VIN. To prevent large vo ltage transients, a low ESR input capacitor sized for the maximum RMS current must be used. The maximum RMS capacitor current is given by: I OMAX ሾVOUTሺVIN െV OUTሻሿଵ/ଶ VIN This formula has a maximum at V IN = 2V OUT, where I RMS = I OUT/2. This simple worst-case condition is commonly used for design because even significant deviations do not offer much relief. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. A 4.7 μF ceramic capacitor for most application is sufficient. INDUCTOR SELECTION For most applications, the value of the inductor will fall in the range of 1 μH to 4.7 μH. Its value is chosen based on the desired ripple current. Large value inductor lower ripple current and small value inductor result in higher ripple currents. Higher V IN or V OUT also increases the ripple current as shown in the following equation: ∆IL ൌ VOUT ൈ ሺVIN െV OUTሻ VIN ൈLൈf ୭ୱୡ A reasonable starting point for setting ripple current is I△ L=240mA (40% of 600mA). The DC current rating of the in ductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation. Different core materials and shapes will change the size/current and price/current relationship of an inductor. The choice of which
V0.1 9(12) 1.5MHz 600mA Synchronous Step-Down Converters with Low Quiescent Current CE8501 Series style inductor to use often depends more on the price vs. size requirements and any radiated field/EMI requirements than on what the CE8501 requires to operate. Table 3 shows some typical surface mount inductors that work well in CE8501 applications. Table 3.Representative Surface Mount Inductors PART NUMBER VALUE (μH) MAX DCR (mΩ) MAX DC CURRENT (A) SIZE W×L×H (mm3) Sumida CDRH 3D16 2.2 3.3 4.7 110 162 1.20 1.10 0.90 3.8×3.8 ×1.8 Sumida CR43 2.2 3.3 4.7 71.2 86.2 108.7 1.75 1.44 1.15 4.5×4.0 ×3.5 Sumida CDRH 4D18 2.2 3.3 4.7 110 162 1.32 1.04 0.84 4.7×4.7 ×2.0 OUTPUT CAPACITOR SELECTION The selection of C OUT is driven by the required effective series resistance (ESR). Typically, once the ESR requirement for C OUT has been met, the RMS current rating generally far exceeds the I RIPPLE requirement. The output ripple △VOUT is determined by: ∆ IL ൬ESR 1 8fCOUT Where f = operating frequency, C OUT = output capacitance and I △ L = ripple current in the inductor. For a fixed out put voltage, the output ripple is highest at maxi mum input voltage since I△ L increase with input voltage. Ceramic capacitors with X5R or X7R dielectrics are recommended due to their low ESR and high ripple current. PCB LAYOUT GUIDANCE When laying out the prin ted circuit board, the following suggestions should be taken to ensure proper operation of the CE8501. 1. The power traces, in cluding the GND trace, the SW trace and the V IN trace should be kept short, direct and wide to allow large current flow. Put enough multiply-layer pads when they need to change the trace layer. 2. Keep the switching node, SW, away from the sensitive FB node. 3. The FB pin should di rectly connect to the feedback resistors. The resistive divider R1/R2 must be connected between the (+) plate of C OUT and ground. 4. Connect the (+) plate of C IN to the V IN pin as closely as possible. 5. Keep the (-) plate of C IN and COUT as close as possible. Figure 2a CE8501-1.8V Layout
V0.1 10(12) 1.5MHz 600mA Synchronous Step-Down Converters with Low Quiescent Current CE8501 Series Figure 2b CE8501-Adj Layout
V0.1 1.5MHz z 600mA Sync PACKAG SOT23-5 P chronous Ste GING INFO Package Ou p-Down Conv RMATION utline Dimen 11(12) verters with L N nsions Low Quiesce nt Current CE850
1 Series
V0.1 12(12) 1.5MHz 600mA Synchronous Step-Down Converters with Low Quiescent Current CE8501 Series © Nanjing Chipower Electronics Inc. Chipower cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Chipower product. No circuit patent license, copyrights or other intellectual property rights are implied. Chipower reserves the right to make changes to their products or specif ications without notice. Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete.