AND8323 Compact, Dual 2 A Reference Design with the NCP3120 Prepared by: Jim Hill ON Semiconductor http://onsemi.com Evaluation Board Specification: Characteristic Min Input Voltage 7 Output Voltage Output Current Typ Max Unit Comments 15 V (Note 1) Vout1 3.3 V Vout2 5 V Vout1 0 2 A Vout2 0 2 A Enable Threshold High EN Tied to SEQ 2.0 Sequence Threshold Low EN Tied to SEQ Voltage Ripple Vout1 40 mVpk-pk Vout2 40 mVpk-pk Load Regulation Vout1 0.61 mV/A (Vin = 12 V, Iout = 0.5 - 2 A) Vout2 0.21 mV/A Line Regulation Vout1 1.85 mV/V (Vin = 10.8 - 13.2 V, Iout = 2 A) Vout2 3.53 mV/V 160 °C Oscillator Frequency 300 Thermal Shutdown Dual 2 A DC-DC Converter Dimensions kHz 0.8 1″ X 2″ V EN Tied to SEQ V EN Tied to SEQ Outlined Area 1. Operation down to 4.5 V requires selecting a lower voltage for Vout2. Circuit Description The NCP3120 operates as a voltage-mode, pulse-widthmodulated, (PWM) asynchronous buck converter. Its operating frequency is adjustable with an external resistor to ground from 220 kHz to 750kHz. minimum switching frequency of 220 kHz and a maximum 750kHz. Also, an onboard operational transconductance amplifier (OTA) integrates the error signal to provide high DC accuracy. The NCP3120 also includes an enable and disable function with externally controlled soft start and stop. © Semiconductor Components Industries, LLC, 2008 March, 2008 - Rev. 1 1 Publication Order Number: AND8323/D AND8323 Board Details Figure 1. Top Layer Figure 2. Bottom Layer Figure 3. Silkscreen Layer http://onsemi.com 2 VOUT2 3 R4 13k C6 http://onsemi.com R12 6.81k 120p R7 316k C16 VOUT_2-1 Figure 4. Evaluation Board - Schematic 75k VOUT_2-2 10k R9 R10 1u C7 R15 15 680 C5 47n R6 1.69k C4 C3 10n 33 C15 220 uF 10 uF 10 uF C11 VINT-1 27 12V MBRA340T3 D1 L1 C20 0.1u VINT-2 26 25 28 29 30 31 32 VSW1-1 10k R8 VIN 47n VIN R5 1k C1 14 AGND FB2 15 RT 16 SW1 VIN 10n VSW2-2 C2 VSW2-1 68.1k SW2 R3 7 120p 6 C10 8 VIN U1 NCP3120 VIN 12 SS2 13 COM2 5 9 SW2 10 SW2 11 GND2 VIN FBB2-2 MBRA340T3 D2 4 220 uF C13 3 10 uF 10 uF C19 2 FBB2-1 R14 20 C14 1 FBT2-1 FBT2-2 L2 10 uF 10 uF 220u C17 C18 C12 VSW1-2 C21 0.1u 5V VIN 12V R2 15k 1n R1 47.5k C8 R13 20 R11 100 FBB1-2 FBB1-1 FBT1-1 FBT1-2 3.3V 0.1u C9 VOUT_1-2 VOUT_1-1 VOUT1 AND8323 PG1 24 PG2 23 EN1 22 SEQ1 21 EN2 20 SEQ2 19 TRACK1 18 TRACK2 17 EN-1 EN-2 AND8323 0 .1. ref Falling comp SHDN 1 PG 1 HS protection 1 0 .9 . ref VIN pg 1 Delay COMP 1 R PWM Error Amplifier EOTA 1 HS1 CON TR OL LOGIC 1 FB 1 0o S SW 1 1V GND 1 10 u SS 1 TRACK 1 SS 1 Soft Start & Tracking Control (MUX1) AVIN FB1 10 u OSCILLATOR Signal Voltage 0. 5V RT Overload Protection ref (0.8 V) AGND SHDN 1 SEQ1 EN 1 EN 2 SHDN 1 Power Sequencing 1 SHDN2 AVIN STAR TU P UVL O TH ER MAL SH U TD OWN Power Sequencing 2 Reference 0. 8V ref (0.8 V) GND 2 SHDN1 SHDN2 1V SEQ 2 ref (0 .8V ) SHDN 2 10u SS 2 SS2 TRACK 2 Soft Start & Tracking Control (MUX2) HS protection 2 FB2 VIN 10u 0 .5V Overload Protection 180o COMP 2 S Error Amplifier R PWM EOTA 2 HS 2 CON TR OL LOGIC 2 FB 2 SW 2 PG 2 pg 2 Delay 0 .9 . ref 0 .1. ref Falling comp SHDN 2 Figure 5. Block Diagram - NCP3120 http://onsemi.com 4 AND8323 PIN DESCRIPTION Pin Symbol 1, 31, 32 SW1 2-7 VIN 8 – 10 SW2 11 GND2 12 SS2 13 COMP2 14 AGND 15 FB2 Feedback Pin. Used to set the output voltage of Channel 2 with a resistive divider from the output. 16 RT Resistor select for the oscillator frequency. Connect a resistor from the RT pin to AGND to set the frequency of the master oscillator. 17 TRACK 2 Tracking input for Channel 2. This pin allows the user to control the rise time of the second output. This pin must be tied high in the normal operation (except in the tracking mode). 18 TRACK 1 Tracking input for Channel 1. This pin allows the user to control the rise time of the first output. This pin must be tied high in the normal operation (except in the tracking mode). 19 SEQ2 Sequence pin for Channel 2. I/O used in power sequencing. Connect SEQ to EN for normal opera‐ tion of a standalone device. 20 EN2 21 SEQ1 22 EN1 Enable input for Channel 1. 23 PG2 Power good, open-drain output of Channel 2. Output logic is pulled to ground when the output is less than 90% of the desired output voltage. Tied to an external pull-up resistor. 24 PG1 Power good, open-drain output of Channel 1. Output logic is pulled to ground when the output is less than 90% of the desired output voltage. Tied to an external pull-up resistor. 25 AVIN Input signal supply voltage pin. 26 FB1 Feedback Pin. Used to set the output voltage of Channel 1 with a resistive divider from the output. 27 AGND 28 COMP1 29 SS1 30 GND1 Exposed Pad (GND) Description Switch node of Channel 1. Connect an inductor between SW1 and the regulator output. Input power supply voltage pins. These pins should be connected together to the input signal sup‐ ply voltage pin. Switch node of Channel 2. Connect an inductor between SW2 and the regulator output. Power ground for Channel 2 Soft-start control input for Channel 2. An internal current source charges an external capacitor connected to this pin to set the soft-start time. Compensation pin of Channel 2. This is the output of the error amplifier and inverting input of the PWM comparator. Analog ground; connect to GND1 and GND2. Enable input for Channel 2. Sequence pin for Channel 1. I/O used in power sequencing. Connect SEQ to EN for normal opera‐ tion of a standalone device. Analog ground. Connect to GND1 and GND2. Compensation pin of Channel 1. This is the output of the error amplifier and inverting input of the PWM comparator. Soft-start/stop control input for Channel 1. An internal current source charges an external capacitor connected to this pin to set the soft-start time. Power ground for Channel 1. The exposed pad at the bottom of the package is the electrical ground connection of the NCP3120. This node must be tied to ground. http://onsemi.com 5 AND8323 Performance Information The following Figures show typical performance of the NCP3120 in this evaluation board. 90 95 Vin = 10.8 V Vin = 10.8 V Vin = 13.2 V 90 EFFICIENCY (%) EFFICIENCY (%) 85 Vin = 12 V 80 75 70 Vin = 12 V 85 80 75 65 70 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Iout (A) Iout (A) Figure 6. Efficiency for Vout1 = 3.3 V Figure 7. Efficiency @ Vout2 = 5 V 1.8 2.0 4.998 3.3750 3.3745 4.997 Vin = 13.2 V 3.3740 Vin = 13.2 V 4.996 3.3735 4.995 3.3730 3.3725 Vout (V) Vout (V) Vin = 13.2 V Vin = 12 V 3.3720 4.994 Vin = 12 V 4.993 4.992 3.3715 Vin = 10.8 V 4.991 3.3710 Vin = 10.8 V 4.990 3.3705 3.3700 4.989 0 0.5 1.0 1.5 2.0 0 Iout (A) 0.5 1.0 1.5 2.0 Iout (A) Figure 8. Load Regulation vs. Vin for Vout1 = 3.3 V Figure 9. Load Regulation vs. Vin for Vout1 = 3.3 V http://onsemi.com 6 AND8323 Performance Information - cont. Figure 10. Load Transient - Vout1 (Vin = 12 V, Iout = 200 mA -to- 2 A -to- 200 mA) (CH1 = Vout1, CH4 = Iout1) Figure 11. Load Transient - Vout2 (Vin = 12 V, Iout = 200 mA -to- 2 A -to- 200 mA) (CH1 = Vout2, CH4 = Iout2) Figure 12. Switching Waveforms Vout1, Vout2, VSW1, VSW2 CH1 = Vout1, CH2 = Vout2, CH3 = VSW1, CH4 = VSW2) http://onsemi.com 7 AND8323 Performance Information - cont. Figure 13. Ratiometric Startup of Vout1/2 with Power Good Outputs (CH1 = Vout1, CH2 = Vout2, CH3 = PG1, CH4 = PG2) Figure 14. Switching Waveforms Showing 1805 Phase Shift Operation (CH1 = VSW1, CH2 = VSW2, CH3 = IL1, CH4 = IL2) http://onsemi.com 8 AND8323 Performance Information - cont. Hiccup Overload Protection When the NCP3120 detects an overload condition (FB voltage falls to 0.5 V), switching stops, the soft start capacitor is discharged to 0.1 V and again charged to 1V. The output of the error amplifier is also tied to ground (output transistor is closed) during the soft start capacitor discharge. If the output voltage is still below the overload condition voltage (0.5 V), the cycle repeats, as shown in Figure15. The NCP3120 uses hiccup mode protection to protect the power supply from damage during overload conditions. During normal operation, the external soft start capacitor is pulled up by a current source that delivers 10 mA to the SS pin capacitor. This current source continues to charge the soft start capacitor until it reaches the saturation voltage of the current source (typically 4 V). Figure 15. Hiccup Overload Protection Description (Vin = 12 V) Figure 16. Switching Waveforms Showing Hiccup Overload Protection (CH1 = VSW1, CH2 = VSW2, CH3 = IL1, CH4 = IL2) http://onsemi.com 9 AND8323 Bill of Materials Designator Qty Description Value Toler‐ ance Footprint Manufacturer Part Number Manufacturer C1 1 Ceramic Chip Capacitor, 50 V 120 p ±10% 0603 VJ0603A121JXACW1BC Vishay C2 1 Ceramic Chip Capacitor, 50 V 22 n ±10% 0603 VJ0603Y223KXJCW1BC Vishay C3 1 Ceramic Chip Capacitor, 50 V 680 p ±10% 0603 C1608C0G2E681J TDK C4 1 Ceramic Chip Capacitor, 50 V 10 n ±10% 0603 VJ0603Y103KXACW1BC Vishay C5-6 2 Ceramic Chip Capacitor, 50 V 47 n ±10% 0603 C1608X7R1E473K TDK C7 1 Ceramic Chip Capacitor, 6.3 V 1m ±10% 0603 C1608X5R0J105K TDK C8 2 Ceramic Chip Capacitor, 50 V 1n ±10% 0603 C1608C0G1H102J TDK C9, C20-21 3 Ceramic Chip Capacitor, 16 V 0.1 m ±10% 0603 C1608X7R1C104K TDK C10 1 Ceramic Chip Capacitor, 50 V 120 p ±10% 0603 VJ0603A121JXACW1BC Vishay C11-C13 3 Aluminum Electrolytic 220 mF ±20% HA0 EMZA250ADA221MHA0G United Chemicon C14-16, C19 4 Ceramic Chip Capacitor, 6.3 V 10 mF ±10% 0805 C2012X5R0J106M TDK C17-18 2 Ceramic Chip Capacitor, 16 V 10 mF ±10% 1206 C3216X5R0J106K TDK U1 1 Dual, 2A Buck Converter - - QFN32, 5x5x1 NCP3120MNTXG ON Semiconductor D1-2 2 Schottky Power Rectifier 3A 40 V n/a SMA MBRA340T3 ON Semiconductor R1 1 SMT Resistor 47.5 k ±1% 0603 CRCW060347K5FKEA Vishay R11 1 SMT Resistor 100 ±1% 0603 CRCW0603100RFKEA Vishay R12 1 SMT Resistor 6.81 k ±1% 0603 CRCW06036K81FKEA Vishay R13-14 2 SMT Resistor 20 ±5% 0603 CRCW060320R0JNEA Vishay R15 1 SMT Resistor 15 ±1% 0603 CRCW060315R0FKEA Vishay R2 1 SMT Resistor 15 k ±1% 0603 CRCW060315K0FKEA Vishay R3 1 SMT Resistor 68.1 k ±1% 0603 CRCW060368K1FKEA Vishay R4 1 SMT Resistor 13 k ±1% 0603 CRCW060313K0FKEA Vishay R5 1 SMT Resistor 1k ±1% 0603 CRCW06031K00FKEA Vishay R6 1 SMT Resistor 1.69 k ±1% 0603 CRCW06031K69FKEA Vishay R7 1 SMT Resistor 316 k ±1% 0603 CRCW0603316KFKEA Vishay R8-9 2 SMT Resistor 10 k ±1% 0603 CRCW060310K0FKEA Vishay R10 1 SMT Resistor 75 k ±1% 0603 CRCW060375K0FKEA Vishay 22 mH ±20% ER IHLP4040DZER220M11 Vishay n/a 0.100 Centers n/a 4 PIN Connector 1-640445-4 TYCO L1-2 2 Inductor EN FBB1-2 FBT1-2 VINT VOUT_1-2 VSW1-2 10 GENERIC 2 PIN SIP HEADER 0.100 CENTERS VIN VOUT1-2 3 4 PIN Connector 4 http://onsemi.com 10 AND8323 ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). 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