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Solving the Challenges of Battery Voltage Fluctuations in Automotive Applications

Analog Devices
  • Analog Devices
  • NEXT Mobility

Managing Power Stability: Addressing Battery Voltage Fluctuations in Automotive Applications

In automotive applications, battery voltage is often stepped down from 12V for use during normal operation, but several conditions cause the battery voltage to fluctuate.
Example: During cranking, when the starter motor draws power from the battery to start the engine, a phenomenon occurs where the battery voltage temporarily drops significantly.

Because components like ECUs and car navigation systems are required to continue operating without interruption even during cranking, their power supply must be capable of boosting the battery voltage.

For this reason, a buck-boost DC/DC converter is typically used as the first power stage after the battery.
However, a known challenge with H-bridge buck-boost converters is their poor responsiveness and the resulting output voltage instability during the transition between step-down and step-up modes.

MAX20039/MAX20040 Solves the Issue

As a solution to this challenge, we introduce the MAX20039/MAX20040 from the former Maxim company.
The MAX20039/MAX20040 are H-bridge buck-boost converters that can perform seamless switching between boost and buck operation modes. They limit the voltage drop during these mode transitions to within ±3%.
Additionally, the four FETs that form the buck-boost converter are integrated into the IC, which enables a reduction in PCB size.

  • 参考図Buck-boost power train archtecture and operation table

    Buck-boost power train archtecture and operation table

  • 参考図Positive line-transienr response

    Positive line-transienr response

  • 参考図Negative line-transienr response

    Negative line-transienr response

* Waveform diagrams and other figures are excerpted from the source below.

MAX20039 / MAX20040 Features

/MAX20039MAX20040
VIN (V) (min)2
VIN (V) (max)40
VOUT1 (V) (max)12
IOUT1 (A) (max)0.61.2
Switch TypeInternal
Preset VOUT (V)5
Output Adjust. MethodPreset, Resistor
Synchronous Switching?Yes
Power Good SignalYes
# DC-DC Outputs1
Alternate TopologyStep-Down, Step-Up, Step-Up/Down
Switching Frequency (kHz)200, 300, 400, 500, 1000, 2200
Design ToolsEE-Sim
Package/PinsTQFN-CU/20
Oper. Temp. (°C) -40 to +85
 -40 to +125
Budgetary Price (See Notes)1.952.2

Small Solution

600mA/1.2A output current
(1A capability @ 105°C ambient)
4.5V to 36V supply voltage (40V tolerant)
Cold crank support down to 2V input
Fixed output 3.3V/5V and 1% ref on FB pin
Adjustable Fsw 220kHz to 2.2MHz
Seamless transition from buck to boost mode
PGOOD output (96% ± 2%)
SYNC input
Small 16-SW TQFN-EP 4mm x 4mm package

Efficient

Low Iq of 36μA @ VOUT 3.3V no load (EN ‘hi’)
Low Iq of 52μA @ VOUT 5V no load (EN ‘hi’)
＜ 10μA shutdown current (EN ‘lo’)
AEC-Q100, temp range: -40°C to +125°C

Availability

Stock

EvKit

MAX20040EVKIT#

Detail Link

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