AME AME5296 n General Description The AME5296 is a high frequency synchronous stepdown DC-DC cnverter with built internal power MOSFETs. That provides wide 4.5V to 18V input voltage range and 2A continuous load current capability. The AME5296 has synchronous mode operation for higher efficiency over output current load range. 2A, 18V, 500KHz Synchronous Step Down DC/DC Converter n Typical Application VIN 4.5-18V C1 22uF 25V C3 1uF BST R4 10Ω C4 0.1uF VCC SW R1 40.2K SS C4 22nF EN EN GND FB 3.3V 2A VOUT L1 4.7uH AME5296 The AME5296 is current mode control scheme which provides fast transient response. Internal compensation function. n Features IN C2 47uF R3 33K R2 12.7K l Wide 4.5V to 18V Operating Input Range l 100mΩ/40mΩ Low RDS(ON) internal Power MOSFETs l Proprietary Switching Loss Reduction Techn -ique l High Efficiency Synchronous Mode Operation l Fixed 500KHz Switching Frequency l External Programmable Soft Start l OCP and Hiccup l Thermal Shutdown l Output Adjustable from 0.8V l RoHS Compliant and Halogen Free n Application l l l l Rev. A.05 Notebook Systems and I/O Power Digital Set Top Boxes LCD Display, TV Networking, XDSL Modem 1 AME 2A, 18V, 500KHz Synchronous Step-Down DC/DC Converter AME5296 n Functional Block Diagram IN VCC VCC Regulator M RSEN Current Sense Amplifer VCC SS BST Oscillator HS Driver 1pF EN Reference 50pF 400k SW Current Limit Comparator Comparator On Time Control Logic Control VCC LS Driver 1MEG FB Error Amplifer 2 GND Rev. A.05 AME 2A, 18V, 500KHz Synchronous Step Down DC/DC Converter AME5296 n Pin Configuration TSOT-23-8 Top View 8 7 6 AME5296-AEAxxx 1. SS 2. IN 3. SW 4. GND 5. BST 6. EN 7. VCC 8. FB 5 AME5296 1 2 3 4 * Die Attach: Conductive Epoxy n Pin Description Pin No. Pin Name 1 SS Soft-Start Control Input. SS controls the soft-start period. Connect a capacitor from SS to GND to set the soft-start period. 2 IN Supply Voltage. The AME5296 operates from a +4.5V to +18V input rail. C1 is needed to decouple the input rail. Use wide PCB trace to make the connection. 3 SW Switch Node. Connect this pin to an external L-C filter. 4 GND System Ground. This pin is the reference ground of the regulated output voltage. For this reason care must be taken in PCB layout. Suggested to be connected to GND with copper and vias. 5 BST Bootstrap for High Side Gate Driver. Connect a 0.1µF or greater ceramic capacitor from BST to SW pins. 6 EN 7 VCC 8 FB Rev. A.05 Pin Description EN=1 to enable the AME5296. EN=0 to turn-off the AME5296. Bias Supply. Decouple with a 0.1µF-to-1µF cap. Feedback Input. It is used to regulate the output of the converter to a set value via an external resistive voltage divider. 3 AME 2A, 18V, 500KHz Synchronous Step-Down DC/DC Converter AME5296 n Ordering Information AME5296 - x x x xxx x Special Feature Output Voltage Number of Pins Package Type Pin Configuration Pin Configuration A (TSOT-23-8) 4 1. SS 2. IN 3. SW 4. GND 5. BST 6. EN 7. VCC 8. FB Package Type Number of Pins Output Voltage Special Feature E: SOT-2X A: 8 ADJ: Adjustable L: TSOT-23-8 (Low Profile) Rev. A.05 AME 2A, 18V, 500KHz Synchronous Step Down DC/DC Converter AME5296 n Absolute Maximum Ratings Parameter Maximum Unit VIN -0.3 to 19 V VSW -0.3V (-5V for 10ns) to 19V (20V for 5ns) V VBST VSW+6V V -0.3 to 6.5 V All Other Pins Junction Temperature Lead Temperature Storage Temperature 150 o C 260 o C -65 to +150 o C n Recommended Operating Conditions Parameter Symbol Rating VIN 4.5V to 18V VOUT 0.8V to VIN-3V Junction Temperature Range TJ -40 to +125 Ambient Temperature Range TA -40 to +85 Input Voltage Output Voltage Unit V o C n Thermal Information Parameter Package Die Attach Thermal Resistance* (Junction to Case) Thermal Resistance (Junction to Ambient) Symbol Maximum θJ C 55 Unit o TSOT-23-8 Conductive Epoxy Internal Power Dissipation Lead Temperature (Soldering 10sec)** θJA 100 PD 1250 260 C/W mW o C * Measure θJC on backside center of molding compound if IC has no tab. ** MIL-STD-202G 210F Rev. A.05 5 AME 2A, 18V, 500KHz Synchronous Step-Down DC/DC Converter AME5296 n Electrical Specifications VIN=12V, unless otherwise noted. Typical values are at TA=25oC. Parameter Symbol Test Condition Supply Shutdown Current IIN VEN=0V 0.1 µA Supply Current IQ VEN=2V, VFB=1V, VSS=3V 0.7 mA High Side Switch On-Resistance RDS(ON)1 VBST-SW=5V 100 mΩ Low Side Switch On-Resistance RDS(ON)2 VCC=5V 40 mΩ Load Side Switch Leakage Current SW LKG VEN=0V, VSW=12V 0.15 µA Switch Current Limit Typ Max 2.8 Units A Oscillator Frequency fOSC1 VFB=0.75V 500 KHz Fold-back Frequency fFB VFB<400mV 0.25 fSW Maximum Duty Cycle DMAX VFB=700mV 90 95 % -2% 800 2% mV 10 50 nA o o Feedback Voltage VFB -40 C<TA<85 C Feedback Current IFB VFB=800mV EN Rising Threshold VEN_RISING 1.2 1.4 1.6 V EN Falling Threshold VEN_FALLING 1.1 1.25 1.4 V EN Input Current EN Turn Off Delay IEN VUVLO Input Under Voltage Lockout Hysteresis Thermal Hysteresis 2 µA VEN=0V 0 µA 8 µs 3.6 V ∆VUVLO 600 mV VCC 5 V 5 % VCC Load Regulation Thermal Shutdown VEN=2V ENTD-OFF Input Under Voltage Lockout Threshold VCC Regulator 6 Min ICC=5mA TSD 150 o C 20 o C Rev. A.05 AME AME5296 n Detailed Descriptiion Internal VCC Regulator The internal VCC regulator is adjusted 5.0V to provide power to the internal circuits from input voltage VIN. In order to maintain the VCC voltage stably, a 0.1µ F-to-1µF ceramic capacitor is recommended. 2A, 18V, 500KHz Synchronous Step Down DC/DC Converter Thermal Shutdown The AME5296 protects itself from overheating with an internal thermal shutdown circuit. If the junction temperature exceeds the thermal shutdown threshold, the voltage reference is grounded and the shutdown mode is activated. The AME5296 is restarted under control of the soft start automatically when the junction temperature drops 20oC below the thermal shutdown threshold. Enable and Soft Start The EN pin provides electrical on/off control of the regulator. When the EN pin voltage exceeds the lockout threshold voltage, the regulator starts to operate and the soft start begins to charge the external capacitor. If the EN pin voltage is pulled below the lockout threshold voltage, the regulator stops switching and the soft start resets. Connecting the EN pin to ground or to any voltage less than 1.2V will disable the regulator and activate the shutdown mode. To limit the start-up inrush current, a soft-start circuit is used to ramp up the reference voltage from 0V to its final value linearly. The soft start time can be calculated as follows: t SS = 0.8 × CSS ISS Under Voltage Lockout (UVLO) The AME5296 incorporates an under voltage lockout circuit to keep the device disabled when the input voltage VIN is below the UVLO start threshold voltage. During powering up, the internal circuits are held inactive and the soft start is grounded until the input voltage VIN exceeds the UVLO start threshold voltage. Once the UVLO start threshold voltage is reached, the soft start is activated and the device begins to operate. The device operates until the input voltage VIN falls below the UVLO stop threshold voltage. The typical hysteresis in the UVLO comparator is 650mV. Rev. A.05 Over-Current Protection and Hiccup Mode The over-current limiting is implemented by cycle-bycycle monitoring the current through the high side MOSFET. If the peak current exceeds the over-current limit threshold, the high side MOSFET is turned off. When the feedback voltage VFB drops below 0.4V, the oscillator frequency is reduced to about 1/4 of the normal frequency to ensure that the inductor current has more time to decay, thereby preventing runaway. Meanwhile, the AME5296 enters hiccup mode, the average short circuit current is greatly reduced to alleviate the thermal issue and to protect the regulator. Enternal Bootstrap Circuit The external bootstrap circuit contains a capacitor and a resistor. A bootstrap capacitor provides power for the high side MOSFET driver. In order to supply the AC current and maintain the BST-SW voltage stably at the switching condition of the high side MOSFET, a 1µF low ESR ceramic capacitor is recommended. The bootstrap resistor which suggests placing 10Ω is utilized to reduce switching spike voltage and noise. 7 AME AME5296 n Application Information Inductor Selection For most applications, the inductance range is chosen based on the desired ripple current. A larger inductance reduces ripple current; meanwhile, the output ripple voltage decreases. Determine inductance is to allow the peakto-peak ripple current to be approximately 30% of the maximum load current. The inductance value can be calculated by: L= VOUT V × 1 − OUT f × IL VIN Where f is the oscillator frequency, VIN is the input voltage, VOUT is the output voltage, and ∆IL is the peak-to-peak inductor ripple current. Choose an inductor that will not saturate under the maximum inductor peak current, calculated by: I LPEAK = I LOAD + VOUT V × 1 − OUT 2 × f × IL VIN Where ILOAD is the load current. The choice of which style inductor to use mainly depends on the price vs. size requirements and any EMI constraints. The input current to the buck converter is discontinuous; therefore an input capacitor is required to supply the AC current while maintaining the DC input voltage. In order to prevent large voltage drop, a low ESR capacitors is recommended for the best performance. Ceramic capacitors are preferred, but tantalum or low-ESR electrolytic capacitors will also be suggested. Choose X5R or X7R dielectrics when using ceramic capacitors. Since the input capacitor absorbs the input switching current, it requires an adequate ripple current rating. The RMS current in the input capacitor can be estimated by: 8 At VIN = 2VOUT, where ICIN = ILOAD/2 is the worst-case condition occurs. For simplification, use an input capacitor with a RMS 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. 1µF, should be placed as close to the IC as possible. The input voltage ripple for low ESR capacitors can be estimated by: VIN = I LOAD VOUT V × × 1 − OUT C IN × f VIN VIN Where CIN is the input capacitance value. Output Capacitor The output capacitor (COUT) is required to maintain the DC output voltage. Ceramic, tantalum, or low ESR electrolytic capacitors are recommended. Low ESR capacitors are preferred to keep the output voltage ripple low. The output voltage ripple can be estimated by: VOUT = Input Capacitor I CIN = I LOAD × 2A, 18V, 500KHz Synchronous Step-Down DC/DC Converter V VOUT × 1 − OUT VIN VIN VOUT V 1 × 1 − OUT × R ESR + f ×L VIN 8 × f × COUT Where RESR is the equivalent series resistance (ESR) value of the output capacitor and COUT is the output capacitance value. When using ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance which is the main cause for the output voltage ripple. For simplification, the output voltage ripple can be estimated by: VOUT = VOUT V × 1 − OUT 8 × f × L × C OUT VIN 2 Rev. A.05 AME 2A, 18V, 500KHz Synchronous Step Down DC/DC Converter AME5296 When using tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated to: VOUT = V VOUT × 1 − OUT × R ESR VIN f ×L Setting the Output Voltage The output voltage is using a resistive voltage divider connected from the output voltage to feedback pin. It divides the output voltage down to the feedback voltage by the ratio: VFB = VOUT × R2 R1 + R 2 The output voltage is: VOUT = 0.8 × R1 + R 2 R2 n Typical Application Circuits VIN 4.5V~18V Ren1 18K IN CIN2 NS CIN1 22uF BST C3 1uF C5 22nF Rev. A.05 C4 0.1uF AME5296 L1 4.7uH VOUT 3.3V/2A SW EN Ren2 10K R4 10Ω VCC R1 40.2K SS R3 33K FB C6 15pF COUT 1 22uF COUT2 22uF R5 0Ω R2 12.7K GND VOUT(V) R1(KΩ) R2(KΩ) R3(KΩ) L(µH) CIN(µF) COUT(µF) 1.0 20.5 82.0 82 1.5 22 22x2 1.2 30.1 60.4 82 1.5 22 22x2 1.8 40.2 32.4 56 2.2 22 22x2 2.5 40.2 19.1 33 3.3 22 22x2 3.3 40.2 12.7 33 4.7 22 22x2 5.0 40.2 7.68 33 6.8 22 22x2 9 AME 2A, 18V, 500KHz Synchronous Step-Down DC/DC Converter AME5296 n Characterization Curve Output Voltage Ripple Load Transient VIN=12V, VOUT=3.3V, IOUT=0.5~2A VOUT (200mV/Div) IL (1A/Div) C3 VOUT (2V/Div) C2 VSW (5V/Div) C3 IL (2A/Div) C4 VEN (5V/Div) V OUT (2V/Div) VSW (10V/Div) C3 C4 Time(2µs/Div) Power On from Input Voltage Power On from Input Voltage V IN (5V/Div) VOUT (2V/Div) VSW (5V/Div) IL (2A/Div) VIN=12V, VOUT=3.3V IOUT=2A C1 C2 C3 C4 Time(5ms/Div) Time(5ms/Div) Power On from EN Power on from EN VEN (5V/Div) C1 C2 C2 VIN=12V, VOUT=3.3V, IOUT=2A Time(200µF/Div) VIN=12V, VOUT=3.3V IOUT=0A C1 C1 VOUT (20mV/Div) IL (2A/Div) C4 VIN (5V/Div) VIN(AC) (100mV/Div) VIN=12V, VOUT=3.3V IOUT=0A VOUT (2V/Div) C1 C2 VIN=12V, VOUT=3.3V IOUT=2A C3 VSW (5V/Div) IL (2A/Div) VSW (5V/Div) IL (2A/Div) C3 C4 Time(5ms/Div) 10 C4 Time(5ms/Div) Rev. A.05 AME 2A, 18V, 500KHz Synchronous Step Down DC/DC Converter AME5296 Power Off from Input Voltage VIN (5V/Div) V OUT (2V/Div) VIN=12V, VOUT=3.3V, IOUT=0A Power Off from Input Voltage V IN (5V/Div) VOUT (2V/Div) C1 C3 VEN (5V/Div) VOUT (2V/Div) VSW (5V/Div) IL (2A/Div) C4 C1 C1 C2 C2 VSW (5V/Div) IL (2A/Div) VIN=12V, VOUT=3.3V, IOUT=2A VSW (5V/Div) C3 IL (2A/Div) C4 Time(50ms/Div) Time(5ms/Div) Power Off from EN Power Off from EN VIN=12V, VOUT=3.3V, IOUT=0A VEN (5V/Div) VOUT (2V/Div) C2 C2 VSW (5V/Div) C3 C3 IL (2A/Div) C4 VOUT (1V/Div) C4 Time(2s/Div) Time(5ms/Div) Short Circuit Entry Short Circuit Recovery VIN=12V, VOUT=3.3V, IOUT=0A VIN=12V, VOUT=3.3V, IOUT=0A VSS (1V/Div) VSW (10V/Div) IL (5A/Div) VOUT (1V/Div) C3 C2 C1 C4 Time(5ms/Div) Rev. A.05 VIN=12V, VOUT=3.3V, IOUT=2A C1 C3 VSW (10V/Div) VSS (1V/Div) C1 IL (5AD/iv) C4 C2 Time(5ms/Div) 11 AME 2A, 18V, 500KHz Synchronous Step-Down DC/DC Converter AME5296 Efficiency 12V 18V VOUT =5V, IOUT =0~2A 100 100 90 90 80 Efficiency (%) Efficiency (%) 18V Efficiency 70 60 50 40 30 20 10 0 12V 5V VOUT=3.3V, IOUT =0~2A 80 70 60 50 40 30 20 10 0.0 0.5 1.0 1.5 2.0 0 0.0 0.5 1.0 1.5 2. 0 Output Current (A) Output Current (A) Efficiency 5V 12V 18V VOUT =1.2V, IOUT =0~2A 100 Efficiency (%) 90 80 70 60 50 40 30 20 10 0 0.0 0. 5 1.0 1.5 2. 0 Output Current (A) 12 Rev. A.05 AME 2A, 18V, 500KHz Synchronous Step Down DC/DC Converter AME5296 n Tape and Reel Dimension TSOT-23-8 P0 W AME AME PIN 1 P Carrier Tape, Number of Components Per Reel and Reel Size Package Carrier Width (W) Pitch (P) Pitch (P0) Part Per Full Reel Reel Size TSOT-23-8 8.0±0.1 mm 4.0±0.1 mm 4.0±0.1 mm 3000pcs 180±1 mm n Package Dimension TSOT-23-8 Top View Side View D L b E E1 0.25 PIN 1 e C e1 A A1 A2 Front View Rev. A.05 13 www.ame.com.tw E-Mail: [email protected] 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. , October 2014 Document: A018A-DS5296-A.05 Corporate Headquarter AME, Inc. 8F, 12, WenHu St., Nei-Hu Taipei 114, Taiwan . Tel: 886 2 2627-8687 Fax: 886 2 2659-2989