EVM Performance Specification Summary
2
EVM Performance Specification Summary
See Data Sheet “Recommended Operating Conditions” for component adjustments. For details about the
resistor programmable settings, see bq25570 data sheet (
MIN
NOM
MAX
UNIT
V
IN
(DC)
DC input voltage into VIN_DC
0.13
4.0
V
V
IN_Start-up
(DC)
DC minimum start-up voltage into depleted storage element, no load attached
330
mV
to VSTOR or VOUT and IBAT
LEAK
<=1uA
V
BAT_OV
Battery Over Voltage Threshold –min and max values i/- 2% set point
4.04
4.18
4.32
V
accuracy and +/-1% resistor tolerance but excludes effects of output ripple
V
OUT
Buck Converter Output Voltage for I
VOUT
< 95 mA - min and max values
1.75
1.8
1.85
V
i/- 2% set point regulation accuracy and +/-1% resistor tolerance but
excludes effects of output voltage ripple, line regulation and load regulation
OK_HYST indication toggles high when VSTOR ramps up - min and max
2.70
2.79
2.88
V
values i/- 2% set point accuracy and +/-1% resistor tolerance
V
BAT_OK
OK_PROG indication toggles low when VSTOR ramps down - min and max
2.89
2.99
3.09
V
values i/- 2% set point accuracy and +/-1% resistor tolerance
MPPT
Maximum Power Point Tracking, Resistor Programmed % of Open Circuit
80%
Voltage
C
BAT
A 100 µF low leakage ceramic capacitor is installed on the EVM as the
100
µF
minimum recommended equivalent battery capacitance.
See
spreadsheet tool to assist with modifying the MPPT, VBAT_OV, VBAT_OK and VOUT
resistors for your application.
CAUTION
If changing the board resistors or the capacitor on VREF_SAMP (C2), it is
important to remember that residual solder flux on a board has a resistivity in
the 1-20 M
Ω
range. Therefore, flux remaining in parallel with changed 1-20 M
Ω
resistors can result in a lower effective resistances, which will produce different
operating thresholds than expected. Similarly flux remaining in parallel with the
VREF_SAMP capacitor provides an additional leakage path, which results in
the input voltage regulation set point drooping during the 16-s MPPT cycle.
Therefore, it is highly recommended that boards be throughly cleaned twice,
once after removing the old components and again after installing the new
components. If possible, the boards should be cleaned until the wash solution
measures ionic contamination greater than 50 M
Ω
.
3
Test and Measurment Summary
Test Setup Tips
Energy harvesting power sources are high impedance sources. A source-meter configured as a current
source with voltage compliance set to the harvester's open circuit voltage is the best way to simulate the
harvester. When simulating a HiZ energy harvester with low output impedance lab power supply, it is
necessary to simulate the harvester's impedance with a physical resistor between the supply, V
PS
, and V
IN
of the EVM. When the MPPT sampling circuit is active, V
IN
= V
PS
= the harvester open circuit voltage
(VOC) because there is no input current to create a drop across the simulated impedance (that is, open
circuit); therefore, VPS should be set to the intended harvester's open circuit voltage. When the boost
converter is running, it draws only enough current until the voltage at VIN_DC droops to the MPPT's
sampled voltage that is stored at VREF_SAMP.
7
SLUUAA7A – July 2013 – Revised August 2014
User's Guide for bq25570 Battery Charger Evaluation Module for Energy
Harvesting
Copyright © 2013–2014, Texas Instruments Incorporated