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

Mar 13 2023

Description

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

Table 1. Bill of Materials
Designator	Value	Description	Part	Footprint	Manufacturer	Quantity
C1	100µF/35	Capacitor	EEVFK1V101P	8mm x 10.2mm	Panasonic	1
C2, C3, C4, C17, C18	0.1µF/25V	Capacitors	GRM188R71E104KA01D	603	Murata	5
CC7, C75	22µF/6.3V	Capaitors	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
D1, D2	30V, 55mA	Schottky Diodes	MBR0530	SOD123	ON Semiconducort	2
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	2
R3	4.7Ω	Resistors	SMD, 1%, 0.125W	603	Vishay	3
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	6.9kΩ	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)	Analog	1

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

Table 2. Efficiency Data for V_OUT2 Disabled: f_SW = 2MHz, L_OUT = 4.7µH, C_OUT = 22µF/6.3V (ceramic)
V_IN (V)	I_IN (A)	V_OUT1 (V)	I_OUT1(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 V_OUT1 Disabled: f_SW = 2MHz, L_OUT = 4.7µH, C_OUT = 22µF/6.3V (ceramic)
V_IN (V)	I_IN(A)	V_OUT2 (V)	I_OUT2 (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