BQ25713 datasheet(88/111 Pages) TI2

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DESIGN PARAMETER

EXAMPLE VALUE

Input Current Limit (2)

3.2 A for 65-W adapter

Battery Charge Voltage(1)

8400 mV for 2s battery

Battery Charge Current(1)

3072 mA for 2s battery

Minimum System Voltage(1)

6600 mV for 2s battery

(1)

Refer to battery specification for settings.

(2)

Refer to adapter specification for settings for Input Voltage and Input Current Limit.

9.2.2 Detailed Design Procedure

The parameters are configurable using the evaluation software. The simplified application circuit (see Figure

9-1, as the application diagram) shows the minimum component requirements. Inductor, capacitor, and MOSFET

selection are explained in the rest of this section. Refer to the EVM user's guide for the complete application

schematic.

9.2.2.1 Input Snubber and Filter for Voltage Spike Damping

During adapter hot plug-in, the parasitic inductance and input capacitor from the adapter cable form a second

order system. The voltage spike at VBUS pin maybe beyond IC maximum voltage rating and damage IC. The

input filter must be carefully designed and tested to prevent overvoltage event on VBUS pin.

There are several methods to damp or limit the overvoltage spike during adapter hot plug-in. An electrolytic

capacitor with high ESR as an input capacitor can damp the overvoltage spike well below the IC maximum pin

voltage rating. A high current capability TVS Zener diode can also limit the overvoltage level to an IC safe level.

However these two solutions may not save cost or have small size.

A cost effective and small size solution is shown in Figure 9-2. The R1 and C1 are composed of a damping RC

network to damp the hot plug-in oscillation. As a result the over voltage spike is limited to a safe level. D1 is used

for reverse voltage protection for VBUS pin. C2 is VBUS pin decoupling capacitor and it should be placed as

close as possible to VBUS pin. C2 value should be less than C1 value so R1 can dominate the equivalent ESR

value to get enough damping effect. R2 is used to limit inrush current of D1 to prevent D1 getting damage when

adapter hot plug-in. R2 and C2 should have 10-µs time constant to limit the dv/dt on VBUS pin to reduce inrush

current when adapter hot plug in. R1 has high inrush current. R1 package must be sized enough to handle

inrush current power loss according to resistor manufacturer’s data sheet. The filter components' value always

need to be verified with real application and minor adjustments may need to fit in the real application circuit.

R1(2010)

2.2 F

0.47-1 F

R2(0805)

Adapter

connector

VBUS pin

Figure 9-2. Input Filter

9.2.2.2 ACP-ACN Input Filter

The BQ25730 has average current mode control. The input current sensing through ACP/ACN is critical to

recover inductor current ripple. Parasitic inductance on board will generate high frequency ringing on ACP-

ACN which overwhelms converter sensed inductor current information. It is also difficult to manage parasitic

inductance created based on different PCB layout. Larger parasitic inductance will generate larger sense current

ringing which could cause the average current control loop to go into oscillation. Therefore ACP-ACN sensing

information need to be conditioned.

For real system board condition, we suggest using below circuit design to get best result and filter noise induced

from different PCB parasitic factor. With time constant of filter from 47 ns to 200 ns, the filter is effective and the

delay of on the sensed signal is small, therefore there is no concern for average current mode control. If 400-kHz

BQ25730

SLUSE65A – FEBRUARY 2021 – REVISED JANUARY 2024

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