AP3421,A,B BCDSEMI | Alldatasheet

Document overview

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Technical content

Features

  • V O1=1.8 to 3.6V at 1A
  • V O2=1.0 to 3.6V at 1A
  • Switching Frequency: 1.3MHz
  • 180° Phase Shifted Switching
  • No Rectifier Diode Required
  • Optional External Clocking (2× Clock Required)
  • Light Load Pulse Skipping
  • Enable/Sleep State
  • Internal Soft-start
  • Open-drain Power On Reset Monitors Input and
  • Outputs
  • Discharge-Before-Turn-On (For AP3421/A)
  • Pre-bias Function (For AP3421B)
  • Peak Over Current Protection
  • Short Circuit Protection
  • Over Temperature Shutdown

Applications

  • Hard Disk Drivers
  • Set Top Boxes

Figure 1. Package Type of AP3421/A/B

Figure 2. Pin Configuration of AP3421/A/B (Top View)

3 PVIN

5 PGND

7 E/S

P r e l i m i n a r y D a t a s h e e t 1.3MHz, Dual 1.0A Synchronous Step-down Converters AP3421/A/B May. 2011 Rev. 1.3 BCD Semiconductor Manufacturing Limited Pin Description (Continued) Pin Number Pin Name Function

8 POR

Power on reset output pin. Monitors FB1, FB2 output voltage levels and V IN. POR is pulled low if an output voltage drop is detected on FB1 or FB2 or VIN, and is Hi-Z during normal operation

9 VMON

Voltage monitor–supervisor for one external voltage (could be input voltage). The POR output is triggered if this output falls below the VMON threshold 10 FB1 Feedback from VO1. Connect voltage divider to the load side of VO1 output inductor-capacitor filter 11 AGND Signal ground connection. Provide a star connection between this pin and PGND pin

Figure 3. Functional Block Diagram of AP3421/A/B

P r e l i m i n a r y D a t a s h e e t 1.3MHz, Dual 1.0A Synchronous Step-down Converters AP3421/A/B May. 2011 Rev. 1.3 BCD Semiconductor Manufacturing Limited

Ordering Information

A: AP3421A B: AP3421B Blank: AP3421 P a c k a g e DN: DFN-3×3 - 1 0 Package Temperature Range Part Number Marking ID Packing Type AP3421DNTR-G1 BCB AP3421ADNTR-G1 BDD DFN-3×3-10 -40 to 85°C AP3421BDNTR-G1 BDE Tape & Reel BCD Semiconductor's Pb-free products, as designated with "G1" suffix in the part number, are RoHS compliant and green. Absolute Maximum Ratings (Note 1) Parameter Symbol Value Unit Input Voltage V IN -0.3 to 7 V Feedback Voltage V FB -0.3 to V IN+0.3 V E/S Pin Voltage V E/S -0.3 to V IN+0.3 V SW1, SW2 Pin Voltage V SW V PGND-1 to VIN+1 V Thermal Resistance θJA 33 ºC /W Operating Junction Temperature T J 150 ºC Storage Temperature T STG -25 to 150 ºC Lead Temperature (Soldering, 10sec) T LEAD 260 ºC Note 1: Stresses greater than those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under “Recommended Operating Co nditions” is not implied. Exposure to “Absolute Maximum Ratings” for extended periods may affect device reliability. Recommended Operating Conditions Parameter Symbol Min Max Unit AP3421 4.5 5.5 Input V oltage V IN AP3421A/B 3.0 5.5 V VO1 Maximum Output Current I O1 (Max) 1 A VO2 Maximum Output Current I O2 (Max) 1 A Operating Ambient Temperature T A -40 85 °C G1: Green TR: Tape & Reel

P r e l i m i n a r y D a t a s h e e t 1.3MHz, Dual 1.0A Synchronous Step-down Converters AP3421/A/B May. 2011 Rev. 1.3 BCD Semiconductor Manufacturing Limited

Electrical Characteristics

VIN =VE/S=5V , TA=25℃, unless otherwise specified. Parameter Symbol Conditions Min Typ Max Unit Supply Current I CC V FB1=VFB2=1.2V 1.0 mA Shutdown Supply Current I SHDN V E/S=0V , VIN=5.0V 10 μA AP3421 3.0 3.5 4.0 Under V oltage Lockout Threshold AP3421A/B Rising Edge 2.4 2.7 3.0 V Under V oltage Lockout Hysteresis V HUVLO 300 mV POR Threshold VMON V VMON_POR V VMON Falling 0.97 1.00 1.03 V Feedback V oltage V FB1, VFB2 0.975 1.0 1.025 V ILIM1 1.2 1.6 Switch Current Limit ILIM2 1.2 1.6 A Oscillator Frequency f OSC1, fOSC2 1.0 1.30 1.60 MHz Soft-start Time t SS_FB1 0.5 1.0 2.0 ms POR Threshold FB1 V FB1_POR FB11Falling1 86 89 92 %V FB1 POR Threshold FB2 V FB2_POR FB21Falling1 86 89 92 %V FB2 Discharge Complete Threshold (AP3421/A ) VFB1_DCT FB1 Level Where Discharge Cycle Is Terminated 50 75 100 mV VEN_L 0.6 V E/S Pin Threshold VEN_H 1.5 fE/S_MIN 1.5 Frequency Lock-in Range fE/S_MAX fSWITCHING=50%×fE/S When Externally Clocked 3.0 MHz POR Assert Delay Time t POR_DELAY Fault Flag Set to POR Pull Low 10 25 40 μs POR Release Delay Time t POR_HOLD Fault Flag Reset to POR Hi-Z State 10 20 30 ms POR Low V oltage V POR_LOW POR Sinking 4mA 300 mV VO2 Start Threshold (AP3421/A ) V FB1_ST FB1 Rising V oltage for FB2 to Initiate Soft-start 86 89 92 %V FB1 SW1, SW2 Discharge Resistance R STOP_SW1,2 Discharge1Resistan- ce for SW1, SW2 15 30 45 Ω RDS_SW1_U 277 RDS_SW2_U VIN=5.0V ISW=100mA 260 RDS_SW1_L 249 AP3421, AP3421A/B RDS_SW2_L VIN=5.0V ISW=-100mA 160 RDS_SW1_U 300 RDS_SW2_U VIN=3.3V ISW=100mA 280 RDS_SW1_L 260 Internal MOSFET on Resistance AP3421A/B R DS_SW2_L VIN=3.3V ISW=-100mA 180 mΩ Thermal Shutdown Threshold T OTSD 160 ºC Thermal Shutdown Hysteresis T HYS 10 20 30 ºC

Figure 12. Start-up from VIN Figure 13. Power-down from VIN

P r e l i m i n a r y D a t a s h e e t 1.3MHz, Dual 1.0A Synchronous Step-down Converters AP3421/A/B May. 2011 Rev. 1.3 BCD Semiconductor Manufacturing Limited

Application Information

  1. Operation The DC-DC converters are current-mode buck converters with a synchronous rectifier and internal compensation. They are designed to be stable with a 1.5μH to 6.8 μH inductor value and 10 μF to 22 μF output capacitor. Both output voltages are resistor programmable. The switching frequency of the converter is fixed and the switches turn on at alternating 180° phase intervals. The converter operates in 2 possible modes: Continuous Mode (CM), and Pulse Skipping Mode (PSM). CM is the default mode under normal loading. Under light loads, PSM mode occurs, where switching cycles are skippe d if the current demand is low. 2. Soft-start The DC-DC converter contains a soft-start function that brings the output voltages up in a slowly increasing ramp with any resistive load from open circuit to 1A (resistive) and any capacitor from 10 μF to 22μF. During soft-start, the peak inductor current shall not exceed 750mA until the output voltage reaches 25% of its final valu e. Current limit shall be active but not trip during soft-start into a rated resistive load. Overshoot voltage during soft-start is limited to 1%. 3. Power Sequencing and Enable When power is applied and if E/S input is asserted (High) or is toggling, the DC-DC converters will enter RUN mode after a short settling period. If the E/S pin is a static low, the IC will enter a SLEEP state where it draws very little input current. When in RUN mode, if there is no fault condition, the VO1 output (SW1) will be the first output to begin soft-start. When the reference voltage for FB1 reaches approximately 90% of the final value, the VO2 output (SW2) will begin soft-start. 4. POR Under voltage comparators are provided to monitor the output voltages and VMON which could be the input voltage. If any of these voltages falls below its POR threshold, a POR open drain output will turn on which pulls the POR pin low. After the POR condition is cleared, there is a delay of 20ms before th the POR output transistor is turned off; when off the POR pin is high-Z and may be pulled up high with a resistor. The POR function has built-in deglitching. Once the POR is detected, the power supply outputs will be discharged prior to restart using the soft-start/sequencing routine. 5.1Over Current and Short Circuit Protection The DC-DC converters shall have over current and short circuit protection. Under any load condition, at any time, any value of load resistor (including 0 Ω) can be applied to the DC-DC outputs instantaneously and held in place indefinitely without the switch current exceeding the peak current limit and without the IC suffering any permanent damage or loss of performance. The output voltage is allowed to drop under over current or short circuit conditions. Recovery to output voltage regulation is required within 10ms of the instant the loading is reduced to maximum allowable rated load; the output voltage shall not exceed the dynamic load excursion limits (±5% excursion) upon recovery. Over current shall not be triggered by a sudden rate of load current change provided the lo ading does not exceed the output load rating of 1A. 6. E/S Function Enable/Synchronization function. Pulling this pin high statically enables the AP3421/A/B while pulling the pin low statically for longer than 4 μs will shut down the AP3421/A/B. Applying a pulse to this pin will synchronize SW1 and SW2 switching frequency to ½ the external clock frequency. The external frequency lock-in ranges from 1.5MHz to 3.0MHz.

Figure 20. Typical Application Circuit of AP3421 (Note 2)

Figure 21. Typical Application Circuit of AP3421A /B (Note 2) 1) Place a 1.0μF capacitor between AVIN pin and AGND for power filtering. 2) Place a 10μF capacitor between PVIN pin and PGND for power filtering.

P r e l i m i n a r y D a t a s h e e t 1.3MHz, Dual 1.0A Synchronous Step-down Converters AP3421/A/B May. 2011 Rev. 1.3 BCD Semiconductor Manufacturing Limited Mechanical Dimensions DFN-3×3-10 Unit: mm(inch)

BCD Semiconductor Manufacturing Limited reserves the right to make changes without further notice to any products or specifi- cations herein. BCD Semiconductor Manufacturing Limited does not assume any responsibility for use of any its products for any particular purpose, nor does BCD Semiconductor Manufacturing Limited assume any liability arising out of the application or use of any its products or circuits. BCD Semiconductor Manufacturing Limited does not convey any license under its patent rights or other rights nor the rights of others. - Wafer Fab Shanghai SIM-BCD Semiconductor Manufacturing Limited 800, Yi Shan Road, Shanghai 200233, China Tel: +86-21-6485 1491, Fax: +86-21-5450 0008 BCD Semiconductor Manufacturing Limited MAIN SITE REGIONAL SALES OFFICE Shenzhen Office Shanghai SIM-BCD Semiconductor Manufacturing Co., Ltd. Shenzhen Office Advanced Analog Circuits (Shanghai) Corporation Shenzhen Office Room E, 5F, Noble Center, No.1006, 3rd Fuzhong Road, Futian District, Shenzhen 518026, China Tel: +86-755-8826 7951 Fax: +86-755-8826 7865 Taiwan Office BCD Semiconductor (Taiwan) Company Limited 4F, 298-1, Rui Guang Road, Nei-Hu District, Taipei, Taiwan Tel: +886-2-2656 2808 Fax: +886-2-2656 2806 USA Office BCD Semiconductor Corporation 30920 Huntwood Ave. Hayward, CA 94544, U.S.A Tel : +1-510-324-2988 Fax: +1-510-324-2788 - IC Design Group Advanced Analog Circuits (Shanghai) Corporation 8F, Zone B, 900, Yi Shan Road, Shanghai 200233, China Tel: +86-21-6495 9539, Fax: +86-21-6485 9673 BCD Semiconductor Manufacturing Limited http://www.bcdsemi.com BCD Semiconductor Manufacturing Limited IMPORTANT NOTICE BCD Semiconductor Manufacturing Limited reserves the right to make changes without further notice to any products or specifi- cations herein. BCD Semiconductor Manufacturing Limited does not assume any responsibility for use of any its products for any particular purpose, nor does BCD Semiconductor Manufacturing Limited assume any liability arising out of the application or use of any its products or circuits. BCD Semiconductor Manufacturing Limited does not convey any license under its patent rights or other rights nor the rights of others. - Wafer Fab Shanghai SIM-BCD Semiconductor Manufacturing Co., Ltd.

800 Yi Shan Road, Shanghai 200233, China

Tel: +86-21-6485 1491, Fax: +86-21-5450 0008 MAIN SITE REGIONAL SALES OFFICE Shenzhen Office Shanghai SIM-BCD Semiconductor Manufacturing Co., Ltd., Shenzhen Office Unit A Room 1203, Skyworth Bldg., Gaoxin Ave.1.S., Nanshan District, Shenzhen, China Tel: +86-755-8826 7951 Fax: +86-755-8826 7865 Taiwan Office BCD Semiconductor (Taiwan) Company Limited 4F, 298-1, Rui Guang Road, Nei-Hu District, Taipei, Taiwan Tel: +886-2-2656 2808 Fax: +886-2-2656 2806 USA Office BCD Semiconductor Corp. 30920 Huntwood Ave. Hayward, CA 94544, USA Tel : +1-510-324-2988 Fax: +1-510-324-2788 - Headquarters BCD Semiconductor Manufacturing Limited No. 1600, Zi Xing Road, Shanghai ZiZhu Science-based Industrial Park, 200241, China Tel: +86-21-24162266, Fax: +86-21-24162277