AME5258 AMETHERM | Alldatasheet
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1.5MHz, 600mA Synchronous Buck Converter Rev.A.05 n Function Diagram Figure 3: Founction Block Diagram GND IN SW UVDET OVDET SWITCHING LOGIC AND BLANKING CIRCUIT Slope COMP OSC 0.6V VREF 0.6V 0.65V 0.55V VFB EN IN ICOMP IRCMP
1.5MHz, 600mA Synchronous Buck Converter Rev.A.05 n Pin Configuration SOT-25 Top View AME5258-AEVxxx 1. EN 2. GND 3. SW 4. IN 5. OUT * Die Attach: Conductive Epoxy SOT-25 Top View AME5258-BEVADJ 1. EN 2. GND 3. SW 4. IN 5. FB * Die Attach: Conductive Epoxy 1 32 5 4 AME5258 1 32 5 4 AME5258 ( Fixed Output ) ( Adjustable Output ) n Pin Description AME5258-AEVxxx AME5258-BEVADJ 1 1 EN Enable Control Input. Forcing this pin above 1.5V enables the part. Forcing this pin below 0.3V shuts down the device. In shutdown, all functions are disabled drawing <1µA supply current. Do not leave EN floating. 2 2 GND Ground Pin 3 3 SW Switch Node Connection to Inductor. This pin connects to the drains of the internal main and synchronous power MOSFET switches. 4 4 IN Main Supply Pin. Must be closely decoupled to GND, Pin2, with a 4.7 µF or greater ceramic capactior. N/A 5 FB Feedback Pin. Receives the feedback voltage from an external resistive divider across the output.
5 N/A OUT Output Voltage for fixed version
1.5MHz, 600mA Synchronous Buck Converter Rev.A.05 n Ordering Information AME5258 - x x x xxx Pin Configuration Package Type Number of Pins Output Voltage A 1. EN E: SOT-2X V: 5 120: 1.2V (SOT-25) 2. GND 180: 1.8V 3. SW 250: 2.5V 4. IN 330: 3.3V 5. OUT B 1. EN E: SOT-2X V: 5 ADJ: Adjustable (SOT-25) 2. GND 3. SW 4. IN 5. FB Pin Configuration Package Type Number of Pins Output Voltage
1.5MHz, 600mA Synchronous Buck Converter Rev.A.05 n Available Options Note: 1. The first 3 places represent product code. It is assigned by AME such as BWM. 2. A bar on top of first letter represents Green Part such as BWM. 3. The last 3 places MXX represent Marking Code. It contains M as date code in "month", XX as LN code and that is for AME internal use only. Please refer to date code rule section for detail information. 4. Please consult AME sales office or authorized Rep./Distributor for the availability of output voltage and package type. n Absolute Maximum Ratings Caution: Stress above the listed in absolute maximum ratings may cause permanent damage to the device. * HBM C: 4000V ~ 6000V Parameter Symbol Maximum Unit Input Supply Voltage VIN 6 V EN, FB Voltages VEN,VFB VIN V SW Voltage VSW -0.3 to (VIN+0.3) V P-Channel Switch Source Current (DC) ISW 900 mA N-Channel Switch Sink Current (DC) ISW 900 mA ESD Classification C* Part Number Marking* Output Voltage Package Operating Ambient Temperature Range AME5258-BEVADJ BWMMXX ADJ SOT-25 -40OC to +85OC AME5258-AEV120 BYRMXX 1.2V SOT-25 -40OC to +85OC AME5258-AEV180 BYJMXX 1.8V SOT-25 -40OC to +85OC AME5258-AEV250 BYNMXX 2.5V SOT-25 -40OC to +85OC AME5258-AEV330 BYFMXX 3.3V SOT-25 -40OC to +85OC
1.5MHz, 600mA Synchronous Buck Converter Rev.A.05 n Thermal Information * Measure θ JC on center of molding compound if IC has no tab. ** MIL-STD-202G 210F n Recommended Operating Conditions Parameter Symbol Rating Unit Ambient Temperature Range TA -40 to +85 oC Junction Temperature Range TJ -40 to +125 oC Storage Temperature Range TSTG -65 to +150 oC Parameter Package Die Attach Symbol Maximum Unit Thermal Resistance* (Junction to Case) SOT-25 θ JC 81 oC / W Thermal Resistance (Junction to Ambient) SOT-25 θ JA 260 oC / W Internal Power Dissipation SOT-25 PD 400 mW 350 oCSolder Iron (10 Sec)** Conductive Epoxy
1.5MHz, 600mA Synchronous Buck Converter Rev.A.05 n Electrical Specifications TA=25oC. VIN=3.6V unless otherwise specified. Parameter Symbol Min Typ Max Units Input Volatge VIN 2.5 5.5 V Feedback Current IFB ±30 nA Regulated Feedback Voltage VFB 0.5880 0.6 0.6120 V VOUT=1.2V, IOUT=100mA 1.164 1.2 1.236 VOUT=1.8V, IOUT=100mA 1.746 1.8 1.854 VOUT=2.5V, IOUT=100mA 2.425 2.5 2.575 VOUT=3.3V, IOUT=100mA 3.201 3.3 3.399 VIN=3V, V FB=0.5V Duty Cycle < 35% AME5258-BEVADJ VIN=3V, V OUT=90% Duty Cycle < 35% AME5258-AEVxxx Shutdown Current ISD 0.1 1 1.2 1.5 1.8 MHz 210 kHz RDSON of P-Channel FET RDSON(P) 0.4 0.6 Ω RDSON of N-Channel FET RDSON(N) 0.35 0.5 Ω Switch Leakage Current ISW ±1 µA EN Input Threshold (High) VEH 1.5 EN Input Threshold (Low) VEL 0.3 EN Input Current IEN ±1 µA 300 450 VEN=0V, VIN=4.2V VFB=0.5V or V OUT=90% VEN=VIN=4.2V V VFB=0V or VOUT=0V µA VIN=2.5V & IOUT=100mA Reference Voltage Line Regulation Δ VFB Oscillator Frequency fOSC Switch Current Limit ICL Quiescent Current Regulated Output Voltage Output Voltage Line Regulation IQ VΔ VOUT Test Condition VIN=2.5V to 5.5V ISW= -100mA ISW=100mA VEN=0V, VSW=0V or 5V,VIN=5V 0.04 0.4AME5258-BEVADJ AME5258-BEVADJ %/V Output Voltage Load Regulation VLOADREG REGLINE VIN=2.5V to 5.5V AME5258-AEVxxx %/V0.40.04 %0.5 0.75 A1
1.5MHz, 600mA Synchronous Buck Converter Rev.A.05 n Detailed Description The AME5258 uses a constant frequency, current modestep-down architecture. Both the main (P-channel MOSFET) and synchronous (N-channel MOSFET) switches are internal. During normal operation, the inter- nal top power MOSFET is turned on each cycle when the oscillator sets the RS latch, and turned off when the cur- rent comparator, ICOMP, resets the RS latch. The peak inductor current at which ICOMP resets the RS latch, is controlled 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 current starts to reverse, as indicated by the current reversal com- parator IRCMP, or the beginning of the next clock cycle. The comparator OVDET guards against transient over- shoots >7.8% by turning the main switch off and keeping it off until the fault is removed. Main Control Loop At light loads, the inductor current may reach zero or reverse on each pulse. The bottom MOSFET is turned off by the current reversal comparator, IRCMP, and the switch voltage will ring. This is discontinuous mode operation, and is normal behavior for the switching regulator. Pulse Skipping Mode Operation Short-Circuit Protection When the output is shorted to ground, the frequency of the oscillator is reduced to about 210kHz, 1/7 the nomi- nal frequency. This frequency foldback ensures that the inductor current has more time to decay, thereby pre- venting runaway. The oscillator's frequency will progres- sively increase to 1.5MHz when VFB or VOUT rises above 0V. n Application Information Dropout Operation As the input supply voltage decreases to a value ap- proaching the output 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 it 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 remem- ber is that at low input supply voltages, the RDS(ON) of the P-channel switch increases (see Typical Performance Characteristics). Therefore, the user should calculate the power dissipation when the AME5258 is used at 100% duty cycle with low input Voltage. Inductor Selection For most applications, the value of the inductor will fall in the range of 1µH to 4.7µH. Its value is chosen based on the desired ripple current. Large value inductors lower ripple current and small value inductors result in higher ripple currents. Higher VIN or VOUT also increases the ripple current as shown in equation 1. A reasonable starting point for setting ripple current is IL = 240mA (40% of 600mA). The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation. Thus, a 720mA rated inductor should be enough for most applications (600mA+ 120mA). For better efficiency, choose a low DC-resis- tance inductor. )1(1 L VIN VOUT LfI -××=D VOUT
1.5MHz, 600mA Synchronous Buck Converter Rev.A.05 Inductor Core Selection Once the value for L is known, the type of inductor must be selected. High efficiency converters generally cannot afford the core loss found in low cost powdered iron cores, forcing the use of more expensive ferrite or mollypermalloy cores. Actual core loss is independent of core size for a fixed inductor value but it is very depen- dent on the inductance selected. As the inductance in- creases, core losses decrease. Unfortunately, increased inductance requires more turns of wire and therefore cop- per losses will increase. Ferrite designs have very low core losses and are preferred at high switching frequen- cies, so design goals can concentrate on copper loss and preventing saturation. Ferrite core material saturates "hard", which means that inductance collapses abruptly when the peak design current is exceeded. This result in an abrupt increase in inductor ripple current and conse- quent output voltage ripple. Do not allow the core to satu- rate! Different core materials and shapes will change the size/current and price/current relationship of an inductor. Toroid or shielded pot cores in ferrite or permalloy mate- rials are small and don't radiate energy but generally cost more than powdered iron core inductors with similar char- acteristics. The choice of which style inductor to use mainly depends on the price vs. size requirements and any radiated field/EMI requirements. CIN and COUT Selection The input capacitance, CIN, is needed to filter the trap- ezoidal current at the source of the top MOSFET. To pre- vent large ripple voltage, a low ESR input capacitor sized for the maximum RMS current should be used.RMS cur- rent is given by : This formula has a maximum at VIN = 2VOUT, where IRMS = IOUT/2. This simple worst-case condition is commonly used for design because even significant deviations do not offer much relief. Note that ripple current ratings from capacitor manufacturers are often based on only 2000 hours of life which makes it advisable to further derate the capacitor, or choose a capacitor rated at a higher tem- perature than required. Several capacitors may also be paralleled to meet size or height requirements in the design. The selection of COUT is determined by the effective series resistance (ESR) that is required to minimize voltage ripple and load step transients, as well as the amount of bulk capaci- tance that is necessary to ensure that the control loop is stable. Loop stability can be checked by viewing the load transient response as described in a later section. The output ripple, VOUT, is determined by : 1)( -××= VOUT VIN VIN VOUTmaxIOUTIRMS úû ù êë é ×+D£D COUTf ESRILVOUT The output ripple is highest at maximum input voltage since IL increases with input voltage. Multiple capacitors placed in parallel may be needed to meet the ESR and RMS current handling requirements. Dry tantalum, spe- cial polymer, aluminum electrolytic and ceramic capaci- tors are all available in surface mount packages. Special polymer capacitors offer very low ESR but have lower capacitance density than other types. Tantalum capaci- tors have the highest capacitance density but it is impor- tant to only use types that have been surge tested for use in switching power supplies. Aluminum electrolytic capacitors have significantly higher ESR but can be used in cost-sensitive applications provided that consideration is given to ripple current ratings and long term reliability. Ceramic capacitors have excellent low ESR characteris- tics but can have a high voltage coefficient and audible piezoelectric effects. The high Q of ceramic capacitors with trace inductance can also lead to significant ringing Using Ceramic Input and Output Capacitors Higher values, lower cost ceramic capacitors are now becoming available in smaller case sizes. Their high ripple current, high voltage rating and low ESR make them ideal for switching regulator applications. However, care must be taken when these capacitors are used at the input and output. When a ceramic capacitor is used at the input and the power is supplied by a wall adapter through long wires, a load step at the output can induce ringing at the input, VIN. At best, this ringing can couple to the output and be mistaken as loop instability. At worst, a sudden inrush of current through the long wires can potentially cause a voltage spike at VIN large enough to damage the part.
1.5MHz, 600mA Synchronous Buck Converter Rev.A.05 Pluse Skipping Mode Pluse Skipping Mode VIN=3.6V VOUT=1.8V IOUT=10mA SW 5V/Div VOUT 10mV/Div IL 20mA/Div 1mS/Div SW 5V /Div VOUT 10mV/Div IL 20mA/Div VIN=3.6V VOUT=1.8V IOUT=50mA 1mS/Div Pluse Skipping Mode VIN=3.6V VOUT=1.8V IOUT=20mA SW 5V/Div VOUT 10mV/Div IL 20mA/Div 1mS/Div Start-UP form Shutdown Load Step Efficiency vs Input voltage 100 2.5 3 3.5 4 4.5 5 5.5 Efficiency(%) IOUT=200mA IOUT=100mA IOUT=600mA IOUT=10mA Input Voltage(V) RUN 2V /Div VOUT 1V/Div IL 500mA/Div VIN=3.6V VOUT=1.8V ILOAD=600mA 200mS/Div AC COUPLED VIN=3.6V VOUT=1.8V ILOAD=0mA to 600mA VOUT 100mV/Div IL 500mA/Div IOUT 500mA/Div 20mS/Div
1.5MHz, 600mA Synchronous Buck Converter Rev.A.05 Oscillator Frequency VS Temperature Oscillator Frequency VS Supply Voltage 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.5 3.5 4.5 5.5 Frequency(MHz) Supply Voltage(V) VFB vs Temperature RDS(ON) vs Input voltage RDS(ON) vs Temperature Efficiency vs Load Current 100 1 10 100 1000 Efficiency(%) IOUT (mA) VOUT=1.2V VIN=2.7V VIN=3.3V VIN=4.2V 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 -50 -25 0 +25 +50 +75 +100 +125 Frequency(MHz) Temperature(oC) 0.585 0.588 0.591 0.594 0.597 0.600 0.603 0.606 0.609 0.612 0.615 -50 -25 0 +25 +50 +75 +100 +125 VFB(V) Temperature(oC) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 RDS(ON) (mW) Main Switch Synchronous Switch Input Voltage(V) 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 -50 -25 0 +25 +50 +75 +100 +125 RDS(ON) (mW) Temperature(oC) VIN=2.7V VIN=3.6V VIN=4.2V Main Switch Synchronous Switch
1.5MHz, 600mA Synchronous Buck Converter Rev.A.05 Efficiency vs Load Current 100 1 10 100 1000 Efficiency(%) IOUT (mA) VOUT=1.5V VIN=2.7V VIN=3.3V VIN=4.2V Efficiency vs Load Current 1 10 100 1000 Efficiency(%) IOUT (mA) VOUT=1.8V VIN=2.7V VIN=3.6V VIN=4.2V 100 1 10 100 1000 Efficiency(%) IOUT (mA) VOUT=2.5V VIN=2.7V VIN=3.6V VIN=4.2V Efficiency vs Load Current Output Voltage vs Load Current Current Limit vs Input Voltage 1000 1100 1200 1300 1400 1500 1600 1700 1800 Temperature (oC) Current Limit (A) 1.774 1.784 1.794 1.804 1.814 1.824 1.834 1.844 0 100 200 300 400 500 600 700 800 900 VOUT(V) IOUT (mA)
1.5MHz, 600mA Synchronous Buck Converter Rev.A.05 Package Carrier Width (W) Pitch (P) Part Per Full Reel Reel Size SOT-25 8.0±0.1 mm 4.0±0.1 mm 3000pcs 180±1 mm n Tape and Reel Dimension SOT-25 Carrier Tape, Number of Components Per Reel and Reel Size W P AME AME PIN 1 n Date Code Rule 1: January 7: July 2: February 8: August 3: March 9: September 4: April A: October 5: May B: November 6: June C: December Month Code Year A A A M X X xxx0 A A A M X X xxx1 A A A M X X xxx2 A A A M X X xxx3 A A A M X X xxx4 A A A M X X xxx5 A A A M X X xxx6 A A A M X X xxx7 A A A M X X xxx8 A A A M X X xxx9 Marking
1.5MHz, 600mA Synchronous Buck Converter Rev.A.05 n Package Dimension SOT-25 MIN MAX MIN MAX A 0.90 1.30 0.0354 0.0512 A1 0.00 0.15 0.0000 0.0059 b 0.30 0.55 0.0118 0.0217 D 2.70 3.10 0.1063 0.1220 E 1.40 1.80 0.0551 0.0709 e H 2.60 3.00 0.10236 0.11811 L q1 0o 10o 0o 10o 0.37BSC 0.0146BSC 0.95BSC 0.0374BSC 1.90 BSC 0.07480 BSC SYMBOLS MILLIMETERS INCHES L Top View Side View Front View D e E H b A PIN 1
Life Support Policy: These products of AME, Inc. are not authorized for use as critical components in life-support devices or systems, without the express written approval of the president of AME, Inc. AME, Inc. reserves the right to make changes in the circuitry and specifications of its devices and advises its customers to obtain the latest version of relevant information. AME, Inc. , February 2009 Document: 1265-DS5258-A.05 Corporate Headquarter AME, Inc. 2F, 302 Rui-Guang Road, Nei-Hu District Taipei 114, Taiwan. Tel: 886 2 2627-8687 Fax: 886 2 2659-2989 www.ame.com.tw E-Mail: sales@ame.com.tw