1
Introduction
2
Considerations When Testing the bq25040 IC
3
Performance Specification Summary
Introduction
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The bq25040 is an integrated Li-ion linear battery charger targeted at space-limited portable applications.
It operates from either a USB port or ac adapter and charges a single-cell, Li-Ion battery with up to 1.1 A
of charge current. The bq25040 has a single-power output that charges the battery. A system load can be
placed in parallel with the battery. The charge current is programmed using the ISET and EN/SET inputs.
The charge current is programmable to USB100, USB500, or a user-programmed charge current up to 1.1
A. Additionally, a 4.9-V, 3%, 50-mA LDO is integrated into the integrated circuit (IC) for supplying
low-power external circuitry. The single-input interface (EN/SET) is used to select the charge current and
to place the bq25040 into Production Test Mode (PTM). In PTM, the bq25040 operates as a linear
regulator without a battery connected, where the output is regulated at 4.2 V and supplies up to 2.3 A to
calibrate GSM transceivers.
The battery is charged in three phases: conditioning, constant current, and constant voltage. In all charge
phases, an internal control loop monitors the IC junction temperature and reduces the charge current if an
internal temperature threshold is exceeded.
The charger power stage and charge current sense functions are fully integrated. The charger function
has accuracy current and voltage regulation loops, charge status display, and charge termination.
The input current is regulated by the ISET loop or may be restricted by the USB current-limit circuitry
when in either USB100 or USB500 mode.
The input connection to the LDO is connected upstream of the charge-sense circuit and is not part of the
current-regulation or current-limit circuit. It is the designer's responsibility to ensure that excessive loading
on the LDO output does not exceed USB specifications. The USB500 mode is set for a 400-mA current
limit so that the LDO load does not cause the USB500 limit to be exceeded.
The LEDs can be run from any power source and are connected to the LDO from the factory. Moving the
resistor from R20 to R21 connects the LEDs to the battery. Note that as the battery voltage decreases, the
illuminated LED dims.
JMP6 is a connection to an onboard pulse generator circuit that can program the desired mode via pulses.
Use only one shunt on JMP1 through JMP5 to program one through five pulses, respectively. The pulse
generator always starts or stops in the low state, which leaves the IC in its active state. The part can only
be programmed once unless it is reset by cycling power or removing JMP6. Removing JMP6 allows
EN/SET to be pulled high and disables the IC. Reapplying the shunt to JMP6 pulls EN/SET low and
enables the IC to the USB500 mode. Toggling switch S1 from the UP position to the DOWN position and
back UP delivers the program pulse(s) to the IC.
SPECIFICATION
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Input dc voltage, V
IN
In recommended voltage range
4.75
5
6.5
V
Reduced performance range, Vin
Voltage outside recommended range
(1)
3.5
30
V
Power dissipation
Pdiss = (V
IN
Vout)
(1)
Iout
(2)
1.5
W
I
OUT
R1 = 1k
0.5
0.8
A
(1)
Input voltage range is specified for normal operation. Input voltage between UVLO and 4.75 V has limitations and may have
some functionality, but does not damage the IC nor present any safety issue with the battery. Input voltage above OVP and less
than 30 Vdc has no operation and will not damage the IC. Lower input voltage (closer to dropout operation) produces less heat
dissipation and potentially better performance.
(2)
The junction temperature rise above ambient is proportional to the power dissipation. Once the junction temperature reaches
~125
°
C, thermal regulations reduces the charge current when not in PTS mode.
2
1.1-A, Single-Input, Single-Cell, Li-Ion Battery Charger With 50-mA LDO and 2.3-A Production Test Support
SLUU358 – April 2009