How to Use the MAX15005 Curren

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Abstract: This reference design shows how to use a MAX15005 automotive power-supply controller as a boost circuit to maintain a constant voltage during an automotive cold-crank condition.

IntroductionWhen an automotive engine remains in a cold climate or is subjected to freezing temperatures for a long time, the engine oil becomes very viscous. In cold temperatures the battery’s internal resistance also increases from its normal value. If the engine is started during that time, the starter motor needs more torque, which draws more current from the battery. Due to transients in the current requirement and high-series resistance, the battery voltage can drop as low as 2.5V. This is known as the cold-crank condition in automotives.

The MAX15005 is a current-mode controller that operates from 4.5V to 40V. The device can manage cold-crank conditions and a load-dump condition as well. Once powered, the MAX15005 operates down to 2.5V, thus accommodating a further drop in the battery voltage.

This reference design shows a solution for a cold crank in automotive applications. The design includes the complete schematic, bill of materials (BOM), efficiency measurements, and test results.


Specifications and Design SetupThe design uses the following specifications:

Input voltage: 2.5V to 18V
Output voltage: 12V
Output current: 1A
Output ripple: ±0.6V
Input ripple: ±15mV
Efficiency: 75% with cold crank > 90% for normal operation
Switching frequency: 200kHz The schematic for the above specifications is shown in Figure 1.




Figure 1. Schematic of the MAX15005B boost converter for FSW = 200kHz.

The BOM for this reference design is given in Table 1.

Table 1. Bill of Materials
Designator
Value
Description
Part
Footprint
Manufacturer
Quantity

C1
10μF/25V
Capacitor
GRM32DR71E106KA12L
1210
Murata?
1

C2
1μF/25V
Capacitor
GRM219R71E105KA88D
805
Murata
1

C3
10μF/25V
Capacitor
GRM32DR71E106KA12L
1210
Murata
1

C4, C6
1μF/16V
Capacitor
GRM188R71C105KA12D
603
Murata
2

C5
150pF
Capacitor
GRM1885C1H151JA01D
603
Murata
1

C7
100pF
Capacitor
GRM1885C1H101JA01D
603
Murata
1

C8, C9
330pF
Capacitor
GRM1885C1H331JA01D
603
Murata
2

C10
10nF
Capacitor
GRM188R71H103KA01D
603
Murata
1

C11
0.1μF
Capacitor
GRM188R71H104KA93D
603
Murata
1

D1
30V/500mA Schottky
Schottky diode
MBR0530T1
SOD123
On Semiconductor?
1

D2
30V/500mA Schottky
Schottky diode
MBR0530T1
SOD123
On Semiconductor
1

D3
40V/2A Schottky
Default diode
B240
SMB
Diodes Incorporated
1

L
10μH
Inductor
IHLP-4040DZER100M01
IHLP-4040EZ
Vishay?
1

Q
30V, 17A n-channel MOSFET
n-channel MOSFET
SI7386DP
Power PAKSO-8
Vishay
1

R1
61.9K
Resistor
SMD 1% Resistor
603
Vishay
1

R2, R12
100K
Resistor
SMD 1% Resistor
603
Vishay
2

R3
604Ω
Resistor
SMD 1% Resistor
603
Vishay
1

R4
4.7
Resistor
SMD 1% Resistor
603
Vishay
1

R5
17.8K
Resistor
SMD 1% Resistor
603
Vishay
1

R6
100
Resistor
SMD 1% Resistor
603
Vishay
1

R7, R8
0.07Ω/1W
Resistor
LRCLR2010LF01R070J
2010
IRC
2

R9
20K
Resistor
SMD 1% Resistor
603
Vishay
1

R10
137K
Resistor
SMD 1% Resistor
603
Vishay
1

R11
15.6K
Resistor
SMD 1% Resistor
603
Vishay
1

R13
10.5K
Resistor
SMD 1% Resistor
603
Vishay
1

U1
4.5V to 40V input, automotive flyback/boost/SEPIC, power-supply controller
PWM controller
MAX15005BAUE+
TSSOP-16
Maxim
1

Performance DataThe efficiency vs. load current plots for this design are given in Figure 2. Input voltage was the test parameter.




Figure 2. Load current vs. converter efficiency.

Converter output voltage and load current are shown in Figure 3 and Figure 4 with VIN = 2.5V and VIN = 11V, respectively.




Figure 3. Converter output voltage and load current with VIN = 2.5V.
CH1: output voltage; CH2: MOSFET gate voltage; CH3: output current.




Figure 4. Converter output voltage and load current with VIN = 11V.
CH1: output voltage; CH2: MOSFET gate voltage; CH3: output current.
Murata is a registered trademark of Murata Manufacturing Co., Ltd.
On Semiconductor is a registered service mark of Semiconductor Components Industries, LLC.
Vishay is a registered trademark of Vishay Intertechnology, Inc.