SLUSAH0C – OCTOBER 2011 – REVISED JUNE 2015
5 Description (Continued)
The bq25504 also implements a programmable maximum power point tracking sampling network to optimize the
transfer of power into the device. Sampling the VIN_DC open-circuit voltage is programmed using external
resistors, and held with an external capacitor (CREF).
For example solar cells that operate at maximum power point (MPP) of 80% of their open-circuit voltage, the
resistor divider can be set to 80% of the VIN_DC voltage and the network will control the VIN_DC to operate
near that sampled reference voltage. Alternatively, an external reference voltage can be provide by a MCU to
produce a more complex MPPT algorithm.
The bq25504 was designed with the flexibility to support a variety of energy storage elements. The availability of
the sources from which harvesters extract their energy can often be sporadic or time-varying. Systems will
typically need some type of energy storage element, such as a rechargeable battery, super capacitor, or
conventional capacitor. The storage element ensures that constant power is available when needed for the
systems. The storage element also allows the system to handle any peak currents that cannot directly come from
the input source.
To prevent damage to a customer’s storage element, both maximum and minimum voltages are monitored
against the user programmed undervoltage (UV) and overvoltage (OV) levels.
To further assist users in the strict management of their energy budgets, the bq25504 toggles the battery good
flag to signal an attached microprocessor when the voltage on an energy storage battery or capacitor has
dropped below a preset critical level. This warning should trigger the shedding of load currents to prevent the
system from entering an undervoltage condition. The OV, UV, and battery good thresholds are programmed
All the capabilities of bq25504 are packed into a small-footprint, 16-lead, 3-mm x 3-mm VQFN package.
Copyright © 2011–2015, Texas Instruments Incorporated
Product Folder Links: bq25504
Submit Documentation Feedback