AME5106/5107 Evaluation Board User Guide 1. General Descriptions The AME5106/5107 is 2A/3A, non-synchronous step-down converter with integrated P-channel Power MOS. The PWM operation is able to vary the duty ratio linearly from 0 up to 100%. This device, available in an 8-pin SOP-8 and PDIP-8 package, provides a compact system solution with minimal external components. 2. Features ● Input voltage: 3.6V to 18V. ● Output voltage: 0.8V to Vcc. ● Duty ratio: 0% to 100% PWM control. ● Oscillation frequency: 350KHz. ● Current limit and Enable function. ● Thermal shutdown function. ● Built-in internal SW P-channel MOS. ● SOP-8 and PDIP-8 Package. 3. Applications ● LCD TV / Monitor ● Set-Top Box ● ADSL Modem ● Switch HUB ● Wireless LAN ● Telecom Equipment ● Networking power supply 4. Evaluation Board Schematic (4.1) AME5106/5107 Typical Schematic Vin 4 C3 IN U1 OUT Vout L1 6 R1 3 R2 OUT OCSET 5 EN 4 Vss 2 C2 7 Vss C5 C1 FB 1 C6 C7 C8 R4 8 C4 R3 ON/OFF D1 D2 Figure 1. Rev. B/01-2010 (4.2) AME5107 Typical Schematic for 5V Application Figure 2. 5. Bill of Materials BOM for item (4.2) Location Q’ty C1,C2 2 22uF /25V Ceramic Capacitor C4532X5R1E226M TDK 1812 C4 1 0.1uF /50V Ceramic Capacitor C1608JB1H104K TDK 0603 C6 1 1uF /16V C1608JB1C105M TDK 0603 C8 1 470uF /16V RVZ-MGA5V-RZ ELNA 8×10.5 R1 1 3.92KΩ Chip Resistor FCR05-F-T-3922 PDC 0805 R2 1 20KΩ Chip Resistor FCR05-F-T-2002 PDC 0805 R3 1 16.9KΩ Chip Resistor FCR05-F-T-1692 PDC 0805 R4 1 88.7KΩ Chip Resistor FCR05-F-T-8872 PDC 0805 L1 1 22uH Inductor CDRH127/LDNP-220MC Sumida - D1,D2 2 40V/3A Schottky Rectifier SK34 DIODES SMC U1 1 - 3A Buck Converter AME5107AIZAADJZ AME SOP-8/PP PCB 1 - Blank PCB TM080102 Rev.F AME - 2 - Terminal Blocks EK381V-02P DINKLE - ON/OFF 1 - Switch TS-006S-5-190g HSUAN YI - - 5 - Test Pin - - - - 4 - Plastic Screw S-306 PINGOOD - - 4 - Spacer Support H-6 PINGOOD - Vin&GND, Vout&GND Value Description Ceramic Capacitor Electrolytic Capacitor Part No. Manufacture Package Rev. B/01-2010 6. Operating Instructions (6.1) Connect Vin to the positive point of DC power supply and GND to supply ground. (6.2) Connect Vout to the positive point of E-load and GND to supply ground or parallel an appropriate resistor to pull up the loading. (6.3) Importing a logic signal to EN pin will enable the AME5107. Logic high (VEN>2.0V) switches on AME5107, logic low puts it into low current shutdown mode. 7. Application Information (7.1) Setting Output Voltage The regulated output voltage is set with an external resistor divider (R3 and R4 in Figure 1.) from the output to the VFB pin and is determined by: VOUT = VFB × ( R3 + R4 ) R3 To prevent stray capacitance and noises, locate resistors R3 and R4 close to AME5106/5107. The external resistor sets the output voltage table as below: VOUT R3 R4 12V 6.5KΩ 91KΩ 5V 3.8KΩ 20KΩ 3.3V 2.4KΩ 7.5KΩ 2.5V 2.4KΩ 5.1KΩ 1.8V 2.4KΩ 3KΩ 1.5V 2KΩ 2.5KΩ 1.2V 2.2KΩ 2KΩ 1.0V 3KΩ 1.5KΩ (7.2) Capacitor Selection (7.2.1) Input Capacitor Selection The input capacitor should be chosen to handle the RMS ripple current of a buck converter.The RMS current is calculated as the following equation: I RMS = I OUT × D × (1 − D) Rev. B/01-2010 Select the voltage rating should be 1.25 to 1.5 times greater than the maximum input voltage. Multi-layer ceramic capacitors, which have very low ESR and can easily handle high RMS ripple current. A single 22uF X5R ceramic capacitor is adequate for 200KHz to 500KHz switching frequency applications. To ensure stable operation C1 or C2 should be placed as close to the IC as possible. (7.2.2) Output Capacitor Selection The output ripple voltage ∆Vo of a buck converter is calculated as the following equations: ∆VO = ∆I 1 ESR + ( × f sw × COUT ) 8 Where: ∆Vo is the output ripple voltage. ∆I is the output ripple current. fsw is the switching frequency. Cout is the output capacitance. ESR is the Equivalent Series Resistance of the output capacitor. A 470uF electrolytic capacitor is found adequate for output filtering in this application. (7.3) Inductor Value Calculation The inductor ripple current for a non-synchronous step-down converter in CCM (Continuous Conduction Mode) is calculated by using the following equation: ∆I L = (VO + V D ) × (1 − D) ( f sw × L1) Where: ∆IL is the inductor ripple current. fsw is the switching frequency. L1 is the inductance. Rev. B/01-2010 (7.4) Board Layout Considerations High frequency switching regulators require very careful layout of components in order to get stable operation and low noise. A good PCB layout could make AME5106/5107 work its best performance. (7.5) PCB Layout Example The PCB layout example of AME5106/5107 is for the application of high voltage converts to low voltage. Careful attention must be paid to the PCB layout and component placement. (7.5.1) (7.5.2) (7.5.3) (7.5.4) Suggest using shading inductor to decrease EMI and output noise. L1、D1 and SW should be kept extremely short. C4 should be placed close to AME5106/5107’s pin2 and pin8. C4 and R4 connect to ground of AME5106/5107 first, and then connect to ground of input capacitor to prevent the AME5106/5107 is interfered by noise. (7.5.5) Ripple noise can be improved by using the MLCC(22uF) for input capacitor (C1). Vin C1 IN IN R2 C4 C3 IN OCSET IN GND R1 C2 IN OCSET EN EN GND ON/OFF EN R4 C5 R3 OUT OUT R3 FB FB FB R3 GND VR1 IN GND SW GND GND GND U1 GND C7 GND C8 GND D1 GND SW D2 GND SW OUT C6 GND OUT Vout L1 Test Pin 5 Places SW OUT SW Screw & Spacer 4 Places Figure 3. Rev. B/01-2010 (7.6) Freewheeling Diode Selection The freewheeling diode conduction time is longer than the P-channel Power MOS on time. Therefore, the diode parameters improve the overall efficiency. Use of Schottky diodes as freewheeling rectifiers reduces diode reverse recovery time and the voltage drop across the diode is lower. For this design, a Diodes, Inc. SK34 is chosen, with a reverse voltage of 40V, forward current of 2A/3A, and a forward voltage drop of 0.5V. The freewheeling diode should be place close to the SW pin of the AME5106/5107 to minimize ring due to trace inductance. (7.7) Setting the Current Limiting The current limit threshold is setting by the resistor R1 connecting from VIN to OCSET pin. The internal 100uA sink current crossing the resistor sets the voltage at the pin of OCSET. When the PWM voltage is less than the voltage at OCSET, an Over-Current condition is triggered. The formula to setting the current limit as below: I LOAD × R DS ( ON ) = I OCSET × ROCSET Rev. B/01-2010