AP6508
Document overview
- Manufacturer or author: Diodes Incorporated
- PDF pages: 14
Technical content
Features
- VIN 4.5V to 21V
- VOUT adjustable to 0.8V
- 500kHz switching frequency
- Enable pin
- External Softstart
- Power Good
- Protection o OCP o Thermal Shutdown
- Lead Free Finish/ RoHS Compliant (Note 1)
Applications
- Gaming Consoles
- TV sets and Monitors
- Set Top Boxes
- Distributed power systems
- Home Audio
- Consumer electronics Note: 1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at http://www.diodes.com/products/lead_free.html. Typical Application Circuit IN EN GND FB SW BS AP6508 VOUT VIN VCC RFB 2, 3, 4, 5 AGND SS PG ON OFF 12, 13 Typical Application Circuit 100 0 21 3 LOAD CURRENT (A) Efficiency vs. Load Current V = 12V V = 5V L = 3.3µH IN OUT EFFICIENCY (%) PART OBSOLETE – CONTACT US
500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER AP6508 Document number: DS33437 Rev. 6 - 4 2 of 14 www.diodes.com July 2021 © Diodes Incorporated OBSOLETE – PART DISCONTINUED Pin Descriptions Pin # Name Description 1 IN Supply Voltage. The AP6508 operates from a 4.5V to 21V input rail. C1 is needed to decouple the input rail. Use wide PCB trace to make the connection. 2,3,4,5 SW Switch Output. Use wide PCB trace to make the connection. 6 BST Bootstrap. A capacitor connected between SW and BS pins is required to form a floating supply across the high-side switch driver. 7 EN EN=1 to enable the chip. For automatic start-up, connect EN pin to VIN by proper EN resistor divider as Figure 1 shows. 8 FB Feedback. An external resistor divider from the output to GND, tapped to the FB pin, sets the output voltage. To prevent current limit run away during a short circuit fault condition the frequency fold-back comparator lowers the oscillator frequency when the FB voltage is below 500mV.
9 PG Power Good
10 SS External Softstart
11 VCC BIAS Supply. Decouple with 0.μ1F – 0.22μF cap. And the capacitance should be no more than 0.22μF 12, 13 GND System Ground. This pin is the reference ground for the regulated output voltage. For this reason care must be taken in its PCB layout. Suggested to be connected to GND with copper and vias.
14 AGND Analog Ground
Exposed PAD No internal connection. It is recommended to connect exposed pad to GND plane for optimal thermal performance Functional Block Diagram VCC REGULATOR REFERENCE OSCILLATOR CURRENT SENSING AMPLIFIER LOGIC HS DRIVER BOOST REGULATOR 1IN EN FB GND EA ERROR AMPLIFIER 200kΩ50pF 1pF BST SW PWM COMPARATOR CURRENT LIMIT COMPARATOR 11VCC LS DRIVER VCC 9PG 10SS Power Good Comparator AGND
500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER AP6508 Document number: DS33437 Rev. 6 - 4 3 of 14 www.diodes.com July 2021 © Diodes Incorporated OBSOLETE – PART DISCONTINUED Absolute Maximum Ratings (Note 2) Symbol Parameter Rating Unit VIN Supply Voltage 22 V VSW Switch Node Voltage -0.3 to 23 V VBS Bootstrap Voltage VSW + 6 V VFB Feedback Voltage –0.3V to +6 V VEN Enable/UVLO Voltage –0.3V to +6 V VCOMP Comp Voltage –0.3V to +6 V TST Storage Temperature -65 to +150 °C TJ Junction Temperature +150 °C TL Lead Temperature +260 °C ESD Susceptibility (Note 3) HBM Human Body Model 3 kV MM Machine Model 300 V Thermal Resistance (Note 4) Symbol Parameter Rating Unit θJA Junction to Ambient 52 °C/W θJC Junction to Case 11 °C/W Recommended Operating Conditions (Note 5) Symbol Parameter Min Max Unit VIN Supply Voltage 4.5 21 V TA Operating Ambient Temperature Range -40 +85 °C Notes: 2. Stresses greater than the 'Absolute Maximum Ratings' specified above, may cause permanent damage to the device. These are str ess ratings only; functional operation of the device at these or any other conditions exceeding those indicated in this speci fication is not implied. Device reliability may be affected by exposure to absolute maximum rating conditions for extended periods of time. 3. Semiconductor devices are ESD sensitive and may be damaged by exposure to ESD events. Suitable ESD precautions should be taken when handling and transporting these device. 4. Test condition for SO-8EP: Device mounted on 2"*2" FR -4 substrate PC board, 2oz copper, with minimum recommended pad on top layer and thermal vias to bottom layer ground plane. 5. The device function is not guaranteed outside of the recommended operating conditions.
500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER AP6508 Document number: DS33437 Rev. 6 - 4 4 of 14 www.diodes.com July 2021 © Diodes Incorporated OBSOLETE – PART DISCONTINUED Electrical Characteristics (VIN = 12V, TA = +25°C, unless otherwise noted) Symbol Parameter Test Conditions Min Typ. Max Unit IIN Shutdown Supply Current VEN = 0V 0 µA IIN Supply Current (Quiescent) VEN = 2.0V, VFB = 1.0V 1.2 mA RDS(ON)1 High-Side Switch On-Resistance (Note 6) 120 mΩ RDS(ON)2 Low-Side Switch On-Resistance (Note 6) 20 mΩ SWLKG Switch Leakage Current VEN = 0V, VSW = 0V 0 10 µA ILimit Current Limit 5.8 A FSW Oscillator Frequency VFB = 0.75V 350 500 650 kHz FFB Fold-back Frequency VFB = 300mV 0.3 fSW DMAX Maximum Duty Cycle VFB = 700mV 80 85 % VFB Feedback Voltage TA = -40°C to +85°C 791 807 823 mV IFB Feedback Current VFB = 800mV 10 50 nA VEN_Rising EN Rising Threshold 1.1 1.3 1.5 V VEN_HYS EN Threshold Hysteresis 0.4 V IEN EN Input Current VEN = 2V 2 μA VEN = 0V 0 ENTD-Off EN Turn Off Delay (Note 6) 5 μs PGVth-Hi Power Good Rising Threshold 0.9 VFB PGVth-Lo Power Good Falling Threshold 0.7 VFB PGTD Power Good Delay 20 μs VPG Power Good Sink Current Capability 0.4 V IPG_LEAK Power Good Leakage Current 50 nA ISS Soft-Start Current 10.5 μA INUVVth VIN Under Voltage Threshold Rising 4.0 4.2 4.4 V INUVHYS VIN Under Voltage Threshold Hysteresis 200 mV VCC VCC Regulator 5 V VCC Load Regulation Icc=5mA 5 % TSD Thermal Shutdown 140 °C Note: 6. Guaranteed by design
500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER AP6508 Document number: DS33437 Rev. 6 - 4 5 of 14 www.diodes.com July 2021 © Diodes Incorporated OBSOLETE – PART DISCONTINUED Typical Performance Characteristics 1.05 1.1 1.15 1.2 1.25 1.3 0 5 10 15 20 25 INPUT VOLTAGE Quiescent Supply Current vs. Input Voltage QUIESCENT SUPPLY CURRENT (mA) 0 5 10 15 25 INPUT VOLTAGE (V) Shutdown Supply Current vs. Input Voltage SHUTDOWN SUPPLY CURRENT (µA) 5.02 5.025 5.03 5.035 5.04 5.045 5.05 0 5 10 15 20 25 INPUT VOLTAGE (V) V Regulator Line RegulationCC V (V)CC -10-20 0 2010 30 5040 60 8070 90 TEMPERATURE (°C) Current Limit vs. Temperature 6.6 6.8 6.2 6.4 5.6 5.8 5.2 5.4 CURRENT LIMIT (A) V = 12V V = 1.2V IN OUT -40 1.22 1.2205 1.221 1.2215 1.222 1.2225 1.223 1.2235 1.224 1.2245 1.225 0 5 10 15 20 25 INPUT VOLTAGE (V) Line Regulation vs. Output Current OUTPUT VOLTAGE (V) 1 1.50 0.5 2.5 32 OUTPUT CURRENT (A) Load Regulation vs. Output Current V = 5VIN V = 12VIN 1.208 1.21 1.204 1.206 1.2 1.202 1.196 1.198 1.192 1.194 OUTPUT VOLTAGE (V)
500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER AP6508 Document number: DS33437 Rev. 6 - 4 6 of 14 www.diodes.com July 2021 © Diodes Incorporated OBSOLETE – PART DISCONTINUED Typical Performace Characteristics (cont.) 100 0 21 3 LOAD CURRENT (A) Efficiency vs. Load Current V = 12V V = 5V IN IN V = 1.2VOUT EFFICIENCY (%) 100 0 21 3 LOAD CURRENT (A) Efficiency vs. Load Current V = 12V V = 5V IN IN V = 1.8VOUT EFFICIENCY (%) 100 0 21 3 LOAD CURRENT (A) Efficiency vs. Load Current V = 12V V = 5V IN IN V = 2.5VOUT EFFICIENCY (%) 0 21 3 LOAD CURRENT (A) Efficiency vs. Load Current EFFICIENCY (%) 100 100 0 21 3 LOAD CURRENT (A) Efficiency vs. Load Current V = 12V V = 5V L = 3.3µH IN OUT EFFICIENCY (%)
500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER AP6508 Document number: DS33437 Rev. 6 - 4 7 of 14 www.diodes.com July 2021 © Diodes Incorporated OBSOLETE – PART DISCONTINUED Typcal Performance Characteristics VIN = 12V, VOUT = 1.2V, L = 3.3µH, C1 = 22µF, C2 = 47µF, TA = +25°C, unless otherwise noted. Time- 2µs/div Steady State Test IOUT = 3A Time- 200µs/div Load Transient Test IOUT = 1.5A to 3A. Step at 0.8A/µs Time- 500µs/div Start-up Through Enable (No Load) Time- 2ms/div Start-up through VIN (No load) Time- 50µs/div Shutdown Through Enable (No Load) Time- 50µs/div Shutdown Through Enable (Iout =1A) Time- 50µs/div Short Circuit Entry Time- 100µs/div Short Circuit Recovery
500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER AP6508 Document number: DS33437 Rev. 6 - 4 8 of 14 www.diodes.com July 2021 © Diodes Incorporated OBSOLETE – PART DISCONTINUED Typcal Performance Characteristics VIN = 12V, VOUT = 1.2V, L = 3.3µH, C1 = 22µF, C2 = 47µF, TA = +25°C, unless otherwise noted. Time- 1µs/div Input Voltage Ripple Time- 2µs/div Output Voltage Ripple Time- 1us/div Powergood Rising Threshold Time- 1µs/div Powergood FallingThreshold 90% of VFB 72% of VFB
500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER AP6508 Document number: DS33437 Rev. 6 - 4 9 of 14 www.diodes.com July 2021 © Diodes Incorporated OBSOLETE – PART DISCONTINUED
Application Information
The AP6508 is a 3A current mode, synchronous buck regulator with built in power MOSFETs. current mode control assures excellent line and load regulation and a wide loop bandwidth for fast response to load transients. Figure. 2 depicts the functional block diagram of AP6508. The operation of one switching cycle can be explained as follows. At the beginning of each cycle, HS (high-side) MOSFET is off. The EA output voltage is higher than the current sensing amplifier output, and the current comparator’s output is low. The risin g edge of the 500kHz oscillator clock signal sets the RS Flip- Flop. Its output turns on HS MOSFET. The current sensing amplifier is reset for every switching cycle. When the HS MOSFET is on, inductor current starts to increase. The current sensing amplifi er senses and amplifies the inductor current. Since the current mode control is subject to sub- harmonic oscillations that peak at half the switching frequency, slope compensation is utilized. This will help to stabilize the power supply. This slope compens ation is summed to the current sensing amplifier output and compared to the error amplifier output by the PWM comparator. When the sum of the current sensing amplifier output and the slope compensation signal exceeds the EA output voltage, the RS Flip-Flop is reset and HS MOSFET is turned off. For one whole cycle, if the sum of the current sensing amplifier output and the slope compensation signal does not exceed the EA output, then the falling edge of the oscillator clock resets the flip- flop. The output of the error amplifier increases when feedback voltage (VFB) is lower than the reference voltage of 0.807V. This also increases the inductor current as it is proportional to the EA voltage. When the HS MOSFET turns off, the synchronous LS MOSFET turns on until the next clock cycle begins. There is a “dead time” between the HS turn off and LS turn on that prevents the switches from “shooting through” from the input supply to ground. The voltage loop is internally compensated with the 50pF and 200kΩ RC network. The maximum EAMP voltage output is precisely clamped at 2.1V. Internal Regulator Most of the internal circuitry including the bottom driver are powered from the 5V internal regulator. When Vin is less than 5V, this internal regulator cannot maint ain the 5V regulation and hence the output voltage would also drop from regulation. Enable The enable (EN) input allows the user to control turning on or off the converter. To enable the converter EN must be pulled above the ‘EN Rising Threshold’ and to disable the converter EN must be pulled below ‘EN falling Threshold’ (EN rising threshold – EN threshold Hysteresis). Few conditions on EN function: 1) EN must be pulled low for at least 5us to disable the regulator. 2) The voltage on EN cannot exceed 5V. 3) The AP6508 can be enabled by Vin through a voltage divider as shown in the figure 1 below. VIN EN RTOP RBOT Figure 1. EN Divider Network a max of 4 mA sink current at 0.4 V when de- asserted. goes high if there are no faults.
and power has to be re-cycled to reset the UVLO fault. the thermal protection circuit. Figure 2. Feedback Divider Network Where LΔI is the inductor ripple current. And SWf is the buck converter switching frequency.
rating, which influences the size of the inductor. is recommended for most applications. improved efficiency under light load conditions. the input supply and the switching noise from the device. must hence have a low ESR to minimize the losses. 4.7µF ceramic capacitor is sufficient. Where ΔVis the maximum output voltage overshoot. capacitor will be sufficient. one such as BAT54 or a Schottky that has a low Vf. Figure 3. External Bootstrap Diode
500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER AP6508 Document number: DS33437 Rev. 6 - 4 11 of 14 www.diodes.com July 2021 © Diodes Incorporated OBSOLETE – PART DISCONTINUED
Ordering Information
FE : DFN4030 13 : Tape & Reel Device Package Code Packaging (Note 7) 13” Tape and Reel Quantity Part Number Suffix AP6508FE-13 FE DFN4030-14 3000/Tape & Reel -13 Note: 7. Pad layout as shown on Diodes Inc. suggested pad layout document AP02001, which can be found on our website at http://www.diodes.com/datasheets/ap02001.pdf. Marking Information Y : Year : 0~9 W : Week : A~Z : 1~26 week; ( Top View ) X : A~Z : Green Y W X XX XX : E8 : AP6508 z : represents 52 and 53 a~z : 27~52 week; Part Number Package Identification Code AP6508FE DFN4030-14 E8 Package Outline Dimensions (All Dimensions in mm)
500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER AP6508 Document number: DS33437 Rev. 6 - 4 12 of 14 www.diodes.com July 2021 © Diodes Incorporated OBSOLETE – PART DISCONTINUED Tape Orientation (Note 8) Note: 8. The taping orientation of the other package type can be found on our website at http://www.diodes.com/datasheets/ap02007.pdf
500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER AP6508 Document number: DS33437 Rev. 6 - 4 13 of 14 www.diodes.com July 2021 © Diodes Incorporated OBSOLETE – PART DISCONTINUED IMPORTANT NOTICE 1. DIODES INCORPORATED AND ITS SUBSIDIARIES (“DIODES”) MAKE NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO ANY INFORMATION CONTAINED IN THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTIC ULAR PURPOSE OR NON- INFRINGEMENT OF THIRD PARTY INTELLECTUAL PROPERTY RIGHTS (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION). 2. The Information contained herein is for informational purpose only and is provided only to illustrate the operati on of Diodes products described herein and application examples. Diodes does not assume any liability arising out of the application or use of this document or any product described herein. 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