Texas Instruments BQ25157, Manual

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10.2.1 Design Requirements
The design parameters for the following design example are shown in Table 10-1 below.
Table 10-1. Design Parameters
PARAMETER VALUE
IN Supply Voltage 5 V
Battery Regulation Voltage 4.2 V
LDO Output Voltage LDO (1.8 V)
10.2.2 Detailed Design Procedure
For easy configuration use of the BQ25157 Setup Guide Tool is recommended.
10.2.2.1 Input (IN/PMID) Capacitors
Low ESR ceramic capacitors such as X7R or X5R is preferred for input decoupling capacitors and should be
places as close as possible to the supply and ground pins fo the IC. Due to the voltage derating of the capacitors
it is recommended at 25-V rated capacitors are used for IN and PMID pins which can normally operate at 5 V.
After derating the minimum capacitance must be higher than 1 µF.
10.2.2.2 VDD, LDO Input and Output Capacitors
A Low ESR ceramic capacitor such as X7R or X5R is recommended for the LDO decoupling capacitor. A 4.7-µF
capacitor is recommended for VDD output. For the LDO output a 2.2-µF capacitor is recommended. The
minimum supported capacitance after derating must be higher than 1 µF to ensure stability. The VINLS input
bypass capacitor value should match or exceed the LDO output capacitor value.
10.2.2.3 TS
A 10-KΩ NTC should be connected in parallel to a 10-kΩ biasing resistor connected to ground. The ground
connection of both the NTC and biasing resistor must be done as close as possible to the GND pin of the device
or kelvin connected to it to minimize any error in TS measurement due IR drops on the board ground lines.
If the system designer does not wish to use the TS function for charging control, a 5-kΩ resistor from TS to
ground must be connected.
10.2.2.4 Recommended Passive Components
Table 10-2. Recommended Passive Components
MIN NOM MAX UNIT
C
PMID
Capacitance in PMID pin 1
(1)
10 47 µF
C
LDO
LDO output capacitance 1 2.2 4.7 µF
C
VDD
VDD output capacitance 1 2.2 4.7 µF
C
BAT
BAT pin capacitance 1 – µF
C
IN
IN input bypass capacitance 1 4.7 10 µF
C
INLS
VINLS input bypass capacitance 1 – µF
C
TS
Capacitance from TS pin to ground 0 0 1 nF
(1) For PMID regulation loop stability, for better transient performance a minimum capacitance (after derating) of 10 μF is recommended.
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BQ25157
SLUSEC5 – DECEMBER 2020
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