AME. High Voltage CC/CV Buck Converter AME5265. n Features. n General Description. n Applications. n Typical Application. n Functional Block Diagram

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1 5265 n General Description The 5265 is a specific 40 maximum rating H buck converter that operates in either C/CC mode supports adjustable put voltage and support constant put current at 20KHz switching frequency. Protection features include under voltage protection, over voltage protection, thermal shutdown, and short circuit protection. The device is available in SOP-8/PP package with exposed pad for low thermal resistance. n Applications l Car Charger l Wall Adapter n Features High oltage CC/C Buck Converter l 40 Maximum ating for Input Power l Up to 2.4A Output Current l Adjustable Output oltage l Fixed Cable Compensation l Switching Frequency is 20KHz l CC/C Mode Function l Internal Soft Start l +/-7% CC Current ange by a Current Sense esistor l Hiccup Mode when Short Occur l Auto ecovery l UP, OP, OTP, SCP l SOP-8/PP l ohs Compliant and Halogen Free n Typical Application 8 ~ 36 OUT C 47µF 0K 2 20K CC FB GND BS Ω SW S+ S- COMP 22nF L 47µH D SK34 5 0Ω 3 8.2K C4 3.3nF S 43mΩ 6 0Ω C5 Optional OUT 00µF n Functional Block Diagram IN S+ S- FB 0.8 CC Control Oscillator Current Sense PWM Controller IN BS SW COMP GND

2 5265 High oltage CC/C Buck Converter n Pin Configuration SOP-8/PP Top iew GND CC 2. FB 3. COMP 4. GND 5. S+ 6. S- 7. BS 8. SW * Die Attach: Conductive Epoxy n Pin Description Pin Number Pin Name Pin Description CC Input Power. 2 FB oltage Feedback Pin. 3 COMP Compensation Node. 4 GND Ground. 5 S+ Current Sense. 6 S- Current Sense. 7 BS High Side Gate Drive Boost Input. 8 SW Switching Node. 9 Exposed Pad Ground. 2

3 5265 High oltage CC/C Buck Converter n Ordering Information x x x xxx Output oltage Number of Pins Package Type Pin Configuration Pin Configuration Package Type Number of Pins Output oltage A. CC Z: SOP/PP A: 8 ADJ: Adjustable 2. FB 3. COMP 4. GND 5. S+ 6. S- 7. BS 8. SW (SOP-8/PP) 3

4 5265 High oltage CC/C Buck Converter n Absolute Maximum atings Parameter Maximum Unit Input oltage Switch oltage Boost Switch oltage All Others Pins Electrostatic Discharge (HBM) Junction Temperature Storage Temperature ESD Classification -0.3 to 40 - to IN + SW to SW to o C -65 to +50 o C HBM 2 k MM 200 n ecommended Operating Conditions Parameter Symbol ating Unit Input oltage IN 8 to 36 Output oltage OUT 0.8 to 5.5 Output Current I OUT 0 to 2.4 A Junction Temperature ange T J -40 to +25 o C Ambient Temperature ange T A -40 to +85 o C n Thermal Information Parameter Package Die Attach Symbol Maximum Unit Thermal esistance (Junction to Case) θ JC 9 o C / W Thermal esistance (Junction to Ambient) SOP-8/PP Conductive Epoxy θ JA 84 Internal Power Dissipation P D 450 W Lead Temperature (soldering 0 sec)** 280 o C * Measure θ JC on backside center of molding compound if IC has no tab. ** MIL-STD-202G 20F 4

5 5265 High oltage CC/C Buck Converter n Electrical Specifications Typical values IN =2 with typical T A =25 o C, unless otherwise specified. Parameter Symbol Test Condition Min Typ Max Units IN Operating ange IN 8 36 ULO ising Threshold oltage ULO Input oltage ising 7 ULO Falling Threshold oltage Hys. Input oltage Falling Standby Current I sb OUT =5, No Load 3 ma Feedback oltage FB 0.8 Feedback oltage Accuracy FB % Internal Soft Start Time T SS 0 ms High Site Switch Current Limit 4 A High Site Switch DS(ON) 00 mω Max. Duty Cycle D MAX 85 % Switching Frequency f OSC FB = KHz Current Error Amplifier m Thermal Shutdown T SD 50 o C Thermal Shutdown ecovery Hys. T SD 20 o C Output OP O-OUT OUT x.06 OUT x.2 5

6 n Detailed Description Under oltage Lock (ULO) The 5265 incorporates an under voltage lock circuit to keep the device disabled when IN (the input voltage) is below the ULO rising threshold voltage. Once the ULO rising threshold voltage is reached, the device start-up begins. The device operates until IN falls below the ULO falling threshold voltage. The typical hysteresis in the ULO comparator is. Over oltage Protection The 5265 has put over-voltage protections. The threshold of put OP circuit is minimum 06% x OUT and maximum 20% x OUT respectively. Once the put voltage is higher than the threshold, the high-side MOSFET is turned off. When the put voltage drops lower than the threshold, the high-side MOSFET will be enabled again. Over Current Protection The 5265 cycle-by-cycle limits the peak inductor current to protect embedded switch from damage. Highside switch current limiting is implemented by monitoring the current through the high side MOSFET. Thermal Shutdown The 5265 protects itself from overheating with an internal thermal shutdown circuit. If the junction temperature exceeds the thermal shutdown trip point, the highside MOSFET is turned off. The part is restarted when the junction temperature drops 20 o C below the thermal shutdown trip point Setting the Output oltage The put voltage is using a resistive voltage divider connected from the put voltage to FB. It divides the put voltage down to the feedback voltage by the ratio: FB = the put voltage is: + = 0.8 Inductor Selection High oltage CC/C Buck Converter The inductor is required to supply constant current to the load while being driven by the switched input voltage. A larger value inductor will have a larger physical size and higher series resistance. It will result in less ripple current that will in turn result in lower put ripple voltage. Make sure that the peak inductor current is below the maximum switch current limit. Determine inductance is to allow the peak-to-peak ripple current to be approximately 30% of the maximum load current. The inductance value can be calculated by: L = fs I L in Where f S is the switching frequency, IN is the input voltage, OUT is the put voltage, and Ι L is the peakto-peak inductor ripple current. Choose an inductor that will not saturate under the maximum inductor peak current, calculated by: Where OAD is the load current. The choice of which style inductor to use mainly depends on the price vs. size requirements and any EMI constraints. Input Capacitor 2 I = + LPK I LOAD 2 fs L 2 The input current to the step-down converter is discontinuous, therefore a capacitor is required to supply the AC current while maintaining the DC input voltage. Use low ES capacitors for the best performance. Ceramic capacitors are preferred, but tantalum or low-es electrolytic capacitors will also be suggested. Choose X5 or X7 dielectrics when using ceramic capacitors. in

7 5265 High oltage CC/C Buck Converter Since the input capacitor (C) absorbs the input switching current, it requires an adequate ripple current rating. The MS current in the input capacitor can be estimated by: I C I LOAD in At IN =2 OUT, where I C = OAD /2 is the worst-case condition occurs. For simplification, use an input capacitor with a MS current rating greater than half of the maximum load current. When using ceramic capacitors, make sure that they have enough capacitance to provide sufficient charge to prevent excessive voltage ripple at input. When using electrolytic or tantalum capacitors, a high quality, small ceramic capacitor, i.e. 0.µF, should be placed as close to the IC as possible. The input voltage ripple for low ES capacitors can be estimated by: I LOAD I = C C fs in Where C is the input capacitance value. Output Capacitor The put capacitor () is required to maintain the DC put voltage. Ceramic, tantalum, or low ES electrolytic capacitors are recommended. Low ES capacitors are preferred to keep the put voltage ripple low. The put voltage ripple can be estimated by: Where ES is the equivalent series resistance (ES) value of the put capacitor and is the put capacitance value. When using ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance which is the main cause for the put voltage ripple. For simplification, the put voltage ripple can be estimated by: = in = fs L in = 2 8 fs L in ES in + 8 fs When using tantalum or electrolytic capacitors, the ES dominates the impedance at the switching frequency. For simplification, the put ripple can be approximated to: = fs L in The characteristics of the put capacitor also affect the stability of the regulation system. ectifier Diode Use a Schottky diode as the rectifier to conduct current when the High-Side MOSFET is turned off. The Schottky diode must have current rating higher than the maximum put current and a reverse voltage rating higher than the maximum input voltage. Compensation Components 5265 has current mode control for easy compensation and fast transient response. The system stability and transient response are controlled through the COMP pin. COMP is the put of the internal transconductance error amplifier. A series capacitor-resistor combination sets a pole-zero combination to govern the characteristics of the control system. The DC gain of the voltage feedback loop is given by: FB A DC = LOAD GCS AEA ES Where FB is the feedback voltage (0.8), A EA is the error amplifier voltage gain, G CS is the current sense transconductance and LOAD is the load resistor value. The system has two poles of importance. One is due to the put capacitor and the load resistor, and the other is due to the compensation capacitor (C4) and the put resistor of the error amplifier. These poles are located at: f f P P2 GEA = 2 π C4 A = 2 π EA LOAD 7

8 5265 High oltage CC/C Buck Converter Where G EA is the error amplifier transconductance. The system has one zero of importance, due to the compensation capacitor (C4) and the compensation resistor (3). This zero is located at: The system may have another zero of importance, if the put capacitor has a large capacitance and/or a high ES value. The zero, due to the ES and capacitance of the put capacitor, is located at: In this case, a third pole set by the second compensation capacitor (C5) and the compensation resistor (3) is used to compensate the effect of the ES zero on the loop gain. This pole is located at: The goal of compensation design is to shape the converter transfer function to get a desired loop gain. The system crossover frequency where the feedback loop has the unity gain is important. Lower crossover frequencies result in slower line and load transient responses, while higher crossover frequencies could cause system instability. A good standard is to set the crossover frequency below one-tenth of the switching frequency. To optimize the compensation components, the following procedure can be used.. Choose the compensation resistor (3) to set the desired crossover frequency. 8 f = Z 2 π C4 3 f ES = 2 π f 3 = P 2 π C5 3 ES Determine 3 by the following equation: 2 f 3 = G G c c EA CS FB 2 0. f < G G Where f C is the desired crossover frequency which is typically below one tenth of the switching frequency. EA CS FB 2. Choose the compensation capacitor (C4) to achieve the desired phase margin. For applications with typical inductor values, setting the compensation zero (f Z ) below one-fourth of the crossover frequency provides sufficient phase margin. Determine C4 by the following equation: 4 C4 > 2 π 3 Where 3 is the compensation resistor. 3. Determine if the second compensation capacitor (C5) is required. It is required if the ES zero of the put capacitor is located at less than half of the switching frequency, or the following relationship is valid: 2 π If this is the case, then add the second compensation capacitor (C5) to set the pole f P3 at the location of the ES zero. Determine C5 by the equation: C5 = 3 Setting Contant Current Threshold The put constant current value is set by a sense resistor SEN that between S+ and S-, according to the following equation: I CC =5m/ SEN f c s ES ES f < 2 Output Cable Compensation The put cable compensation voltage can be set by.let =0K, OUT ab 20m/A. The put cable compensation voltage is shown by the page - [Cable Compensation].

9 5265 High oltage CC/C Buck Converter PC Board Lay Guidance When laying the printed circuit board, the following checklist should be used to ensure proper operation of the IC. ) Arrange the power components to reduce the AC loop size consisting of CIN, IN pin, SW pin and the schottky diode. 2) Place input decoupling ceramic capacitor CIN as close to IN pin as possible. CIN is connected power GND with vias or short and wide path. 3) Use copper plane for power GND for best heat dissipation and noise immunity. 4) S+S- trace must be from current sense resistor with Kelvin sense as below figure and away SW node. Top Layer Bottom Layer 9

10 5265 High oltage CC/C Buck Converter n Characterization Curve Power On Power On IN (0/Div) C SW (5/Div) IN (20/Div) C SW (0/Div) IN =2, OAD =.5A IN =24, OAD =.5A OUT (2/Div) OUT (2/Div) (2A/Div) C4 Time(2ms/Div) (2A/Div) C4 Time(2ms/Div) Power Off Power Off IN (0/Div) C IN (20/Div) C SW (0/Div) SW (20/Div) IN =2, OAD =.5A IN =24, OAD =.5A OUT (2/Div) OUT (2/Div) (A/Div) C4 Time(2ms/Div) (A/Div) C4 Time(2ms/Div) 250 IN to F SW 6 OUT vs. TC Switching Frequency (KHz) Output oltage () OUT= Input oltage () Temperature ( o C) 0

11 Efficiency (%) Cable Compensation oltage () 5265 High oltage CC/C Buck Converter n Characterization Curve (Contd.) Output ipple IN =2, Load=0mA Output ipple IN =24, Load=50mA OUT (20m/Div) OUT (50m/Div) SW (0/Div) SW (20/Div) (00mA/Div) C4 (200mA/Div) C4 Time(2µS/Div) Time(2µS/Div) Output ipple IN =2, Load=2400mA Output ipple IN =24, Load=2400mA OUT (50m/Div) OUT (00m/Div) SW (0/Div) SW (20/Div) (2A/Div) C4 (2A/Div) C4 Time(2µS/Div) Time(2µS/Div) Efficiency vs. Output Current Cable Compensation IN=2 IN= =0K Output Current (A) Output Current (A)

12 5265 High oltage CC/C Buck Converter n Characterization Curve (Contd.) Load Transcient IN =2, Load=0-2400mA Load Transcient IN =24, Load=0-2400mA OUT (500m/Div) OUT (500m/Div) (2A/Div) C4 (2A/Div) C4 Time(mS/Div) Time(mS/Div) Short Protection SW (0/Div) OUT (2/Div) (2A/Div) C4 Time(500µS/Div) 2

13 5265 High oltage CC/C Buck Converter n Tape and eel Dimension SOP-8/PP P0 PIN W P Carrier Tape, Number of Components Per eel and eel Size Package Carrier Width (W) Pitch (P) Pitch (P0) Part Per Full eel eel Size SOP-8/PP 2.0±0. mm 8.0±0. mm 4.0±0. mm 2500pcs 330± mm n Package Dimension SOP-8/PP TOP IEW D SIDE IEW SYMBOLS MILLIMETES INCHES MIN MAX MIN MAX A E2 E E L A A C PIN D C E E L b b e FONT IEW A2 A A D e.270 BSC BSC θ 0 o 8 o 0 o 8 o E D

14 Life Support Policy: These products of, Inc. are not authorized for use as critical components in life-support devices or systems, with the express written approval of the president of, Inc., 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., Inc., August 207 Document: A032A-DS5265-B.02 Corporate Headquarter, Inc. 8F, 2 Wenhu St., Nei-Hu District Taipei 4, Taiwan,.O.C. Tel: Fax: