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1 Introduction
1.1 Background
1.2 Performance Specification Summary
User's Guide
SLUU305 – March 2008
bq24085/6/7/8 Evaluation Module
This user’s guide describes the bq24085/6/7/8 evaluation module (EVM) that provides a convenient
method for evaluating the performance of a charge management solution for portable applications using
the bq24085/6/7/8 product family. The charger is designed to deliver up to 750 mA of continuous charge
current for single-cell Li-Ion or Li-polymer applications using a DC power supply.
The bq24085/6/7/8 series are highly integrated Li-Ion and Li-polymer linear chargers, targeted at
space-limited portable applications. The bq24085/6/7/8 series offers a variety of safety features and
functional options, while still implementing a complete charging system in a small package. The battery is
charged in three phases: conditioning, constant or thermally regulated current, and constant voltage.
Charge is terminated based on minimum current. An internal programmable charge timer provides a
backup safety feature for charge termination and is dynamically adjusted during the thermal regulation
phase. The bq24085/6/7/8 automatically re-starts the charge if the battery voltage falls below an internal
threshold; sleep mode is set when the external input supply is removed. Multiple versions of this device
family enable easy design of the bq24085/6/7/8 in cradle chargers or in the end equipment, while using
low-cost or high-end AC adapters.
Table 1 and the accompanying table note gives the EVM performance specifications and qualifications.
Table 1. Performance Specification Summary
SPECIFICATION TEST CONDITIONS MIN TYP MAX UNITS
Input DC Voltage, V
I(DC)
V
REG
+0.5 5 12
(1)
Volts
Battery Charge Current, I
O(CHG)
1
(1)
Amperes
Power Dissipation (V
(DC+)
– V
(BAT+)
) × I
(CHG)
1.5 Watts
(1)
• This maximum recommended IC input voltage is 16.5 V. The IC has an OVP (overvoltage protection) input circuit that
disables the charging circuit if the threshold is exceeded. Most IC selections are set for 6.5 V, but some are set as high as
12 V (see SLUS784 data sheet). The EVM can handle an input voltage up to the recommended maximum of 16.5 V, but
the IC will shut down due to the internal voltage protection.
• It is recommended that in normal operation the IC be designed and run below the thermal regulation junction temperature of
125 ° C. The thermal loop can run continuously without any issues, but the suggested thermal loop operational use is for
more harsh environments where the ambient temperature is high (for example, in an automobile during the summer) or with
an incorrect adaptor with a higher input voltage.
• For typical input and ambient conditions with the PowerPAD™ tied to a copper plane, one can expect 1.5 W of heat
dissipation prior to the thermal loop reducing the current. P
dissIC
= I
CHG
x (V
DC+
- V
BAT+
). For the worst-case, steady-state
thermal condition, V
BAT+
= 3.4 VDC (the battery when transitioning from precharge to fast charge reaches a steady-state
value after approximately 2 minutes). If the thermal regulation limit of 125 ° C is reached, then the charging current is
adjusted lower.
SLUU305 – March 2008 bq24085/6/7/8 Evaluation Module 1
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