Keywords: Dual Converter, Switcher, DC/DC converter, Integrated MOSFET, High Switching Frequency,
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REFERENCE DESIGN 4152  INCLUDES: Tested Circuit Schematic BOM Test Data 

Reference Design for the MAX5073 Dual Buck Converter Operating at a Switching Frequency of 2MHz

Dec 21, 2007

Abstract: The MAX5073 is a dual converter capable of operating as a buck or boost converter. As a dual buck converter, this device can deliver up to 2A and 1A of output current. The reference design focuses on the MAX5073 operating as a buck converter with a switching frequency of 2MHz, which allows the use of smaller passive components and keeps it out of the AM band for automotive applications.

This article shows a detailed reference design using the MAX5073 as a dual buck converter with a switching frequency of 2MHz. This design can be used in applications that are space limited, because the higher switching frequency allows smaller passive components to be used on the board. In addition, this power solution can be used (in conjunction with load-dump protection) for automotive applications that require a switching frequency outside of the AM radio band, such as those found in automotive instrument clusters and infotainment systems.

Key specifications for this reference design are listed below, along with a detailed schematic (Figure 1) and the bill of materials (Table 1) needed for this application.

Specifications

  • Input Voltage: 5.5V to 16V
  • Converter 1 Output Voltage = 3.3V/2A (max)
  • Converter 2 Output Voltage = 2.5V/1A (max)
  • Switching Frequency (fSW) of Each Converter = 2MHz
  • Temperature with Airflow (TA) = -40°C to +85°C
Figure 1. MAX5073 reference design.
More detailed image (PDF)
Figure 1. MAX5073 reference design.

Table 1. Bill of Materials
Designator Value Description Part Footprint Manufacturer Quantity
C1 100µF/35V Capacitor EEVFK1V101P 8mm x 10.2mm Panasonic 1
C2, C3, C4, C17, C18 0.1µF/25V Capacitors GRM188R71E104KA01D 603 Murata 5
C5, C6, C7 22µF/6.3V Capacitors GRM31CR60J226KE19 1206 Murata 2
C8, C9 10µF/25V Capacitors GRM31CR61E106KA12 1206 Murata 1
C10, C12 2.2nF Capacitors GRM188R71H222JA01 603 Murata 2
C11 560pF Capacitor GRM188R71H561KA01 603 Murata 1
C13, C14 22pF Capacitors GRM1885C1H220JA01 603 Murata 2
C15 1nF Capacitor GRM18871H102KA01 603 Murata 1
C16 4.7µF/6.3V Capacitor GRM188R60J475KE19B 603 Murata 1
C19 0.22µF/10V Capacitor GRM188R71A224KA01 603 Murata 1
C20 0.01µF Capacitor GRM188R71H103KA01J 603 Murata 1
D1, D2 30V, 500mA Schottky diodes MBR0530 SOD123 ON Semiconductor 2
D3 40V, 3A Schottky diode MBRS340 SMC ON Semiconductor 1
D4 40V, 2A Schottky diode MBRS240 SMB ON Semiconductor 1
L1, L2 4.7µH Inductors IHLP2525-CZ 6.86mm x 6.47mm x 3.18mm Vishay 1
R1, R11 100kΩ Resistors SMD, 1%, 0.125W 603 Vishay 2
R2 6.8Ω Resistor SMD, 1%, 0.125W 603 Vishay 1
R3 4.7Ω Resistor SMD, 1%, 0.125W 603 Vishay 1
R4, R8, R10 1.18kΩ Resistors SMD, 1%, 0.125W 603 Vishay 3
R5, R9 27.4kΩ Resistors SMD, 1%, 0.125W 603 Vishay 2
R6 10kΩ Resistor SMD, 1%, 0.125W 603 Vishay 1
R7 12.7kΩ Resistor SMD, 1%, 0.125W 603 Vishay 1
R12 2.2Ω Resistor SMD, 1%, 0.125W 603 Vishay 1
R13 6.19kΩ Resistor SMD, 1%, 0.125W 603 Vishay 1
R14 8.76kΩ Resistor SMD, 1%, 0.125W 603 Vishay 1
U1 MAX5073 Dual buck converter MAX5073ETI+ 32-TQFN_EP (5mm x 5mm) Maxim 1

Actual measurements taken from the board showing the efficiency performance are shown in Tables 2 and 3.

Table 2. Efficiency Data for VOUT2 Disabled
fSW = 2MHz, LOUT = 4.7µH, COUT = 22µF/6.3V (ceramic)
VIN (V) IIN (A) VOUT1 (V) IOUT1 (A) Efficiency (%)
14.007 0.065732 3.3371 0.1018 36.8973371
14.010 0.183690 3.3339 0.5122 66.3542117
14.005 0.267750 3.3321 0.8032 71.3722082
14.007 0.329490 3.3309 1.0112 72.9812485
14.005 0.449290 3.3298 1.4007 74.1230723
14.002 0.584520 3.3281 1.8203 74.0201375
14.001 0.650260 3.3267 2.0150 73.6279304

Table 3. Efficiency Data for VOUT1 Disabled
fSW = 2MHz, LOUT = 4.7µH, COUT = 22µF/6.3V (ceramic)
VIN (V) IIN (A) VOUT2 (V) IOUT2 (A) Efficiency (%)
14.008 0.044533 2.5350 0.1075 43.6845979
14.008 0.067144 2.5337 0.2049 55.1967881
14.003 0.087638 2.5337 0.3010 62.1452787
14.004 0.109076 2.5337 0.4003 66.3986847
14.005 0.133680 2.5337 0.5122 69.3178710
14.005 0.155350 2.5338 0.6097 71.0058542
14.008 0.255976 2.5334 1.0001 70.6597037

In terms of stability, bode plots for each output are shown in Figures 2 and 3, detailing the gain and phase of each output.

Figure 2. Bode plot for a VOUTPUT of 3.3V/1.4A.
Figure 2. Bode plot for a VOUTPUT of 3.3V/1.4A.

Figure 3. Bode plot for a VOUTPUT of 2.5V/0.6A.
Figure 3. Bode plot for a VOUTPUT of 2.5V/0.6A.

Related Parts
MAX5073 2.2MHz, Dual-Output Buck or Boost Converter with Internal Power MOSFETs Free Samples  


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APP 4152: Dec 21, 2007
REFERENCE DESIGN 4152, AN4152, AN 4152, APP4152, Appnote4152, Appnote 4152

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