Application Note AP2001 Dual Buck Converter AP2001 Specification

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Application Note AP2001 Dual Buck Converter AP2001 Specification

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ANP007
Application Note AP2001 Dual Buck Converter
AP2001 Specification
Features General Description Assignments Descriptions Block Diagram Absolute Maximum Ratings
Hardware
Introduction Typical Application Input Output Connections Schematic
Bill Material Board Layout
Design Procedure
Introduction Operating Specifications Design Procedures 3.3.1 Selection buck inductor 3.3.2 3.3.3 3.3.4 3.3.5 Selection output capacitor (Cout) Selection power switch (MOSFET) Selection power Rectifier Selection input capacitor (Cin)
Voltage monitor AP434
This application note contains product information. Anachip Corp. reserves rights modify product specification without notice. liability assumed result this product. rights under patent accompany sale product. Rev. Feb. 2003 1/11
ANP007
Application Note AP2001 Dual Buck Converter AP2001 Specification Features
Dual Control Circuitry Operating voltage Adjustable Dead Time Control (DTC) Under voltage Lockout (UVLO) Protection Short Circuit Protection (SCP) Variable Oscillator Frequency. 500Khz 2.5V voltage reference Output 16-pin PDIP packages
General Description
AP2001 integrates Pulse-width-Modulation (PWM) control circuit into single chip, mainly designs power-supply regulator. functions included on-chip 2.5V reference output, error amplifiers, adjustable oscillator, dead-time comparators, UVLO, SCP, circuitry, dual common-emitter (CE) output transistor circuit. Recommend output transistors pre-driver Driving externally. provide from 100%. Switching frequency adjustable trimming During situation, UVLO makes sure that outputs until internal circuit operational normally.
Assignments
View EA1+ EA1FB1 DTC1 OUT1
EA2+ EA2FB2 DTC2 OUT2
PDIP/SOP
Descriptions
Name Description Timing Capacitor Timing Resistor Error Amplifier Input(+) Error Amplifier Input(-) Feedback Loop Compensation Dead Time Control Pre-driver Output Ground Supply Voltage Short Circuit Protection Voltage Reference
Anachip Corp. www.anachip.com.tw 2/11
Rev. Feb. 2003
ANP007
Application Note AP2001 Dual Buck Converter Block Diagram
DTC1
Bandgap Reference
Oscillator
MAX.500KHz
VREF Error Amplifier 170K 1.18V EA2+ Error Amplifier UVLO
Amplifier
OUT1
Amplifier
OUT2
DTC2
Absolute Maximum Ratings
Symbol TLEAD Supply voltage Amplifier input voltage Collector output voltage Collector output current Operating temperature range Storage temperature range Lead temperature mm(1/16 inch) from case seconds Parameter Rating +150 Unit
Anachip Corp. www.anachip.com.tw 3/11
Rev. Feb. 2003
ANP007
Application Note AP2001 Dual Buck Converter Hardware Introduction
dual-buck demo board supply constant output voltage that 3.3V This board supply output power buck1 output buck2 output (3.3V 3A). Using input voltage 10.8 13.2 full load efficiency percent. This type converter converts unregulated input voltage regulated output voltage that they always lower than input voltage. control method used board fixed frequency, variable on-time pulse-width-modulation (PWM). feedback method used voltage-mode control. Other features board include undervoltage lockout (UVLO), short-circuit protection (SCP), adjustable dead time control (DTC).
Typical Application
AP2001 operate either (Continuous Conduction Mode) (Discontinuous Conduction Mode). following applications designed (Continuous Conduction Mode) operation. That inductor current allowed fall zero. compare disadvantage advantage DCM, main disadvantage inherent stability problems (caused right-half-plane zero double pole small-signal control output voltage transfer function). However, main disadvantage that peak currents switch diode larger than when converting. Using power switch output diode with larger current power dissipation ratings should solve this issue large peak current. designer larger output capacitors, take more effort EMI/RFI solution also. Designer could make choice each mode. loading current, preferred buck. load current requirement high, preferred buck. Figure shows basic buck topology. When switch turned energy stored inductor constant voltage VO", inductor current ramps slope determined input voltage. Diode during this period. Once switch, turns off, diode starts conduct energy stored inductor released load. Current inductor ramps down slope determined difference between input output voltages.
Figure Typical Buck Converter Topology
Anachip Corp. www.anachip.com.tw 4/11
Rev. Feb. 2003
ANP007
Application Note AP2001 Dual Buck Converter Input Output Connections
Anachip Corp. www.anachip.com.tw 5/11
Figure Connections
Rev. Feb. 2003
ANP007
Application Note AP2001 Dual Buck Converter Schematic
Figure 2_buck demo board schematic
Anachip Corp. www.anachip.com.tw 6/11 Rev. Feb. 2003
ANP007
Application Note AP2001 Dual Buck Converter Board Materials
Value open Q'ty Part Reference 10nF 470pF B340 470uF CON2 33uH/3A PMOS_SOP8 Description Don't install Ceramic Chip CAP. ±10% 0805 Ceramic Chip CAP. 10nF ±10% 0805 Ceramic Chip CAP. ±10% 0805 Ceramic Chip CAP. 470pF ±10% 0805 Schottky Diode Electrolysis Capacitors Terminal Block TOROID COILS 33uH P-Channel MOSFET -30V 0.6A SOT-23 -40V -0.6A SOT-23 Chip Resistance 1/8W ±10% 0805 Chip Resistance 1/8W ±10% 0805 Chip Resistance 1/8W ±10% 0805 Chip Resistance 1/8W ±10% 0805 Chip Resistance 4.7K 1/8W ±10% 0805 Chip Resistance 1/8W ±10% 0805 Chip Resistance 8.2K 1/8W ±10% 0805 Chip Resistance 5.6K 1/8W ±10% 0805 define 50K) Chip Resistance 1/8W ±10% 0805 Monolithic Dual Channel Controller Manufacturers Philips Philips Philips Philips Philips DIODES DINKLE Star Electronics APEC ROHM DIODES ROHM DIODES Yageo(RL Series) Yageo(RL Series) Yageo(RL Series) Yageo(RL Series) Yageo(RL Series) Yageo(RL Series) Yageo(RL Series) Yageo(RL Series) Yageo(RL Series) Yageo(RL Series) Anachip Part Number
B340A ELK508V-02P CEM4435 AP4435M SST2222A MMBT4401 SST2907A MMBT4403
MMBT4401 MMBT4403 4.7K 8.2K 5.6K 200K AP2001
AP2001S
Anachip Corp. www.anachip.com.tw 7/11
Rev. Feb. 2003
ANP007
Application Note AP2001 Dual Buck Converter Board Layout
Board size 80mm(W)x50mm(L)
Figure Silkscreen layer
Figure layer
Figure Bottom layer
Anachip Corp. www.anachip.com.tw 8/11
Rev. Feb. 2003
ANP007
Application Note AP2001 Dual Buck Converter Design Procedure Introduction
AP2001 integrated circuit dual controller, operates over wide input voltage range. This together with cost makes very popular choice controller. This section will describe AP2001 design procedure. operation design dual-buck converter will also discussed detail.
Operating Specifications
Specification Input Voltage Range Output Buck1 Voltage Range Output Buck2 Voltage Range Output Current (Buck1) Range Output Current (Buck2) Range Operating Frequency Output Ripple Efficiency 10.8 13.2 Units
Table Operating Specifications
Design Procedures
This section describes steps design continuous-mode buck boost converter, explains construct basic power conversion circuits including design control chip functions basic loop. switching frequency chosen. Example calculations accompany design equations. Since this fixed output converter, example calculations apply converter with output voltage 3.3V/5V input voltage unless specified otherwise. first quantity determined converter duty cycle value. Vds(sat)
Duty ratio
Assuming commutating diode forward voltage power switch voltage Vds(sat) 0.1V, duty cycle 3.3V 10.8, 13.2 0.36, 0.32, 0.29 respectively; duty cycle 10.8, 13.2 0.51, 0.46 ,0.42 respectively. 3.3.1 Selection buck inductor buck converter uses single-stage filter. Choose inductor maintain continuous-mode operation down percent (Io(min)) rated output load:
Anachip Corp. www.anachip.com.tw 9/11 Rev. Feb. 2003
ANP007
Application Note AP2001 Dual Buck Converter
0.6A (For 3.3V)
inductor value (Vin Vds(sat) Dmin (Vin Vds(sat) Dmin (13.2 3.3) 0.29 23.7H (200 10^3) (13.2 0.42 (200 10^3)
3.3V
28.4H
choose output voltage "3.3V" "5V".
3.3.2 Selection output capacitor (Cout) Assuming that inductor ripple current flows through capacitor effective series resistance (ESR) zero, capacitance needed 7.5F (200 10^3) 0.05
Cout
Assuming capacitance very large, needed limit ripple 0.05 0.083
output filter capacitor should rated least times calculated capacitance 30-50 percent lower than calculated ESR. This design used 470F/25V OS-Con capacitor parallel with ceramic reduce ESR. 3.3.3 Selection power switch (MOSFET) Based preliminary estimate, RDS(on) should less than 0.10 33m. CEM4435(CET) -30V p-channel MOSFET with RDS(on) 35m. Power dissipation (conduction switching losses) estimated PMOSFET Io^2 Rds(on) Dmax [0.5 Assuming total switching time 55°C maximum ambient temperature, thermal impedance 50°C/W thus: PMOSFET 0.035 0.36) [0.5 (0.15 10^(-6)) (200 10^3) 0.65W
Anachip Corp. www.anachip.com.tw 10/11 Rev. Feb. 2003
ANP007
Application Note AP2001 Dual Buck Converter
(RJA PMOSFET) 0.65) 87.5°C.(For 3.3V) PMOSFET 0.035 0.51) [0.5 (0.15 10^(-6)) (200 10^3) 0.7W (RJA PMOSFET) 0.7) 90°C.(For 3.3.4 Selection Rectifier catch rectifier conducts during time interval when MOSFET off. B340 (DIODES) schottky rectifier power surface-mount package. power dissipation Dmin) 0.29) 1.065W.(For 3.3V) Dmin) 0.42) 0.87W.(For Assuming 55°C maximum ambient temperature, thermal impedance 15°C/W thus: (RJA 1.065) 70.975°C. (For 3.3V) (RJA 0.87) 68.05°C. (For 3.3.5 Selection input capacitor (Cin) current rating input capacitor calculated from following formula. capacitor manufacturers data sheet must checked assure that this current rating exceeded. Iin(rms) (Io(max) Io(min)) (Io(max) Io(min)) (IL^2)/3] [0.36 0.3) 0.3) 0.36/3] 1.8A 3.6A This capacitor should located close using short leads voltage rating should approximately times maximum input voltage. select input capacitor value "470uF/25V".
Voltage monitor AP434
some applications, output voltage concerned high damage avoid being damaged, comparing output voltage with reference could monitor output voltage. AP434 monolithic that includes independent OP-Amp another OP-Amp, which non-inverting input wired fixed voltage reference. AP434 data sheet provides cost space saving voltage monitoring function.
Written Cheng-Yu Chen()
Anachip Corp. www.anachip.com.tw 11/11
Rev. Feb. 2003

Application Note AP2001 Dual Buck Converter AP2001 Specification

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