LM5155EVM-SEPIC User's Guide

The LM5155EVM-SEPIC Evaluation Module (EVM) is designed to showcase the LM5155 wide input voltage Boost/SEPIC/Boost controller, implementing a SEPIC converter with a coupled inductor. The EVM operates at 2.2 MHz, and it produces a regulated output of 12 V 24 W from an input of 5 V to 42 V. When the input voltage is between 3 V to 5 V, the output power is derated down to 10 W. The factory-installed controller is the LM5155-Q1. However, by replacing the IC, the EVM can also be used to demonstrate the performance of the LM51551-Q1, LM5155 and LM51551. The difference between the LM5155-Q1 and LM51551-Q1, or between the LM5155 and LM51551, is that the latter features the hiccup mode for overload protection.

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1 Features and Electrical Performance

The LM5155EVM-SEPIC supports the following features and performance capabilities:

Wide input voltage range from 3 V to 42 V, to cover typical automotive battery voltage ranges including cold cranking and load dump transients
Optimized for input voltage range from 6 V to 18 V
Tightly regulated output voltage of 12 V with a 1% accurate reference voltage
Supports 2 A full load when V_IN is greater than 5 V
Supports 0.8 A load current when V_IN drops to 3 V
2.2 MHz switching frequency
Peak efficiency > 88%
Can evaluate LM51551-Q1, LM5155, and LM51551 ICs, by replacing the factory installed IC with the corresponding IC
Hiccup mode for output over current protection (applicable only with LM51551 and LM51551-Q1)

The electrical performance of the EVM is show in Table 1. The EVM terminals and signal test points are listed in Table 2. The typical application circuit is shown in Figure 2. The EVM complete schematic is shown in Figure 19.

1.1 Electrical Parameters

Table 1. Electrical Performance

Parameter	Test Conditions	MIN	TYP	MAX	UNIT
INPUT CHARACTERISTICS
Input voltage Range V_IN	Normal operation, 2 A full load	6	12	18	V
Input voltage Range V_IN	Maximum transient voltage, 2 A full load	5		42	V
	Power derating from 2 A down to 0.8 A	3		5	V
Input voltage turn on V_IN(ON)	Adjusted by the UVLO/SYNC resistors		2.9		V
Input voltage turn off V_IN(OFF)	Adjusted by the UVLO/SYNC resistors		2.8		V
OUTPUT CHARACTERISTICS
Output Voltage V_OUT			12		V
Maximum Output Current I_OUT	V_IN > 5 V	2			A
Maximum Output Current I_OUT	3 V < V_IN < 5 V	0.8		2	A
Output Voltage V_{OUT_OV}			13.2		V
SYSTEM CHARACTERISTICS
Switching Frequency			2.2		MHz
External Clock Synchronization	Recommended. IC can synchronize to wider frequency range	1.8		2.5	MHz
Full Load Efficiency			88		%
LM5155-Q1 Junction Temperature, T_J		-40		150	C