This design features an automotive backup battery system using a 1S Li battery for emergency operation.

The primary power input is rated for 6- to 18-V nominal (2.7- to 36-V peak) to comply with 12-V automotive requirements. The secondary power input is equipped with a fuel gauge to monitor a single cell Li battery and supports input voltages from 2 V to 4.35 V. The onboard learning load allows the easy implementation of an end-of-life detection for the backup battery.

Both power inputs are connected via ORing MOSFET switches to an 8.5-V boost converter, which can deliver up to 21.5-W continuous output power (30-W peak) with 2.5-V input voltage. At lower output currents, the input voltage of the boost converter can be as low as 2 V.

Due to the ORing MOSFET switches, this boost converter covers the emergency operation as well as cold crank situations, where the 12-V rail can drop down to 2.7 V at the primary input.

An ideal diode together with the bypass function of the boost stage minimizes losses during normal operation and allows low cold-crank voltages. Additionally, the ideal diode allows disconnecting the load on demand.

For ease of evaluation, an automated switchover between primary and secondary power input is implemented on this design.

The total power solution is completed by a linear battery charger for the Li battery, which can operate at input voltages as high as 18 V and withstand 40-V spikes during load dumps. The charger supports various cell chemistries.

The following images shown the top and bottom photos of the 4-layer PCB, FR4, with 35-µm copper.

Board Top

Board Bottom

Block Diagram

Table 1-1 details the board connections, jumpers, and test points.

Table 2-1 describes the pin functions of the individual connectors.

Power up the board:

1. Ensure J16 is shorted.
2. Connect the PMP30963 board to the EV2400 via J2. Ensure 3.3 V are applied to pin 4 of J2.
3. Connect any of the voltage outputs from the EV2400 to J5, pin 6. This pin is used to control the learning load and the EV2400 utilizes the voltage outputs as a control signal.
4. Connect a Li battery to J1/J3. The battery and its connection must be low impedance.
5. Connect a 12-V supply to J10/J14. Ensure that this source is low impedance.
6. Provide the necessary control signals to the following pins of J5: pin 2 (charger enable), pin 12 (booster enable), pin 18 (ideal diode enable).

When all voltages are applied, the ideal diode enable must be pulled high to deliver power to the boost converter.

Now the boost converter and the battery charger can be enabled or disabled using the corresponding control inputs. Switchover between the primary and the secondary power input happens automatically when the voltage at the primary power input drops below approximately 3 V. When the voltage rises above approximately 4.6 V, the boost converter is connected to the primary power input again.

This section includes the thermal image, control loop, and efficiency graphs.