BQ24157S Datasheet, PDF (11/45 Pages) Texas Instruments – Full USB Compliance and USB-OTG Support

Not Recommended for New Designs
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8 Detailed Description
bq24157S
SLUSB76B – FEBRUARY 2013 – REVISED MAY 2015
8.1 Overview
For a current-restricted power source, such as a USB host or hub, a high-efficiency converter is critical to fully
use the input power capacity for quickly charging the battery. Due to the high efficiency for a wide range of input
voltages and battery voltages, the switch mode charger is a good choice for high speed charging with less power
loss and better thermal management than a linear charger.
The bq24157S includes highly integrated synchronous switch-mode chargers, featuring integrated FETs and
small external components, targeted at extremely space-limited portable applications powered by 1-cell Li-Ion or
Li-polymer battery pack. Furthermore, the device has bidirectional operation to achieve boost function for USB-
OTG support.
The bq24157S has three operation modes: charge mode, boost mode, and high impedance mode. In charge
mode, the IC supports a precision Li-ion or Li-polymer charging system for single-cell applications. In boost
mode, the IC boosts the battery voltage to VBUS for powering attached OTG devices. In high impedance mode,
the IC stops charging or boosting and operates in a mode with very-low current from VBUS or battery, to
effectively reduce the power consumption when the portable device is in standby mode. Through I²C
communication with a host (referred to as HOST mode), the IC achieves smooth transition among the different
operation modes. During DEFAULT operation, the charger will still charge the battery but uses each register's
default values.
Table 1. Device Features
Features
VOVP (V)
D4 pin definition
I_CHARGE(MAX) at POR in DEFAULT mode with R_(SNS) = 68 mΩ and OTG = High
I_CHARGE(MAX) in HOST mode with R_(SNS) = 68 mΩ and safety limit register increased from default (A)
Output regulation voltage at POR (V)
Boost function
Input current limit in DEFAULT mode
Battery detection at power up
I²C address
PN1 (bit4 of 03H)
PN0 (bit3 of 03H)
Safety timer and WD timer
100-ms power-up delay
Spread Spectrum
Factory test mode
bq24157S
6.5
OTG
550 mA
1.5
3.54
Yes
100 mA (OTG = Low);
500 mA (OTG = High)
No
6AH
1
0
Disabled
Yes
Yes
Yes
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