EVAL-ADP5090 Datasheet, PDF (4/8 Pages) Analog Devices – Evaluation Board for the ADP5090 Ultralow Power Boost Regulator

UG-708
Input and Output Voltmeter Connections
Measure the input and output voltages with voltmeters. Ensure
that the voltmeters connect to the appropriate test points on the
board. If the voltmeters are not connected to the correct test
points, the measured voltages may be incorrect due to the voltage
drop across the leads, or due to the connections between the
board, the power source, and/or the load. To connect the
voltmeters, use the following procedure:
1. Connect the positive terminal (+) of the input voltage
measuring voltmeter to Test Point TP5 on the evaluation
board.
2. Connect the negative terminal (−) of the input voltage
measuring voltmeter to Test Point TP6 on the board.
3. Connect the positive terminal (+) of the output voltage
measuring voltmeter to Test Point TP2 on the board.
4. Connect the negative terminal (−) of the output voltage
measuring voltmeter to Test Point TP9 on the board.
Powering On the Evaluation Board
If the open circuit voltage (OCV) of the input current source is
above a minimum input voltage of 0.38 V for cold-start
(typical), and the input power is above the 16 μW minimum
input power of cold-start (typical), the EVAL-ADP5090 enters
cold-startup when the SYS voltage is below VSYS_TH. When the
SYS voltage is above VSYS_TH, the board exits cold-startup and
enables the main boost.
After cold-startup, the MPPT sampling circuit is active and the
harvester OCV is detectable because there is no input current to
create a droop across the impedance. The main boost runs and
draws current until the VIN voltage drops to the sampled
MPPT voltage stored at the CBP pin.
Optional BACK_UP Setup
An optional primary battery connected to the BACK_UP pin
can accelerate the cold-startup or maintain the system load.
When the voltage at the BACK_UP pin is higher than the
voltage at the BAT pin, the ADP5090 turns on the internal
power MOSFETs between the BACK_UP pin and the SYS pin.
When the BACK_UP pin voltage is lower than the BAT pin
voltage, the internal power MOSFETs turn off.
EVAL-ADP5090 User Guide
MEASURING THE EVAL-ADP5090 PERFORMANCE
Measuring the Switching Waveform
To observe the switching waveform with an oscilloscope, place
the oscilloscope probe tip at Test Point TP4 with the probe
ground connected to the GND pin. Set the oscilloscope to a dc
coupling, 2 V/division, 10 μsec/division time base. The
switching waveform alternates between 0 V and the
approximate SYS voltage.
Measuring Efficiency
Measure the efficiency, η, by comparing the input power with
the output power. Figure 3 shows the test setup. Float the RDIV
jumper (J3) and provide an external voltage at the CBP pin as
the MPPT voltage so that the input voltage is regulated to this
voltage. With a voltage source meter capable of sinking current
to connect to the SYS pin, obtain the output voltage and output
current.
η  ^{VSYS  ISYS}
V_IN  I_IN
Measuring the Inductor Current
Measure the inductor current by removing one end of the
inductor from the pad on the board and using a wire connected
between the pad and the inductor. Then, use a current probe to
measure the inductor current.
Measuring the Output Voltage Ripple
To observe the output voltage ripple, place an oscilloscope
probe across Output Capacitor C1 with the probe ground lead
placed at the negative capacitor terminal (−) and the probe tip
placed at the positive capacitor terminal (+). Set the oscillo-
scope to an ac coupling, 50 mV/division, 1 sec/division time
base and a 20 MHz bandwidth.
A standard oscilloscope probe has a long wire ground clip. For
high frequency measurements, this ground clip picks up high
frequency noise and injects it into the measured output ripple.
To eliminate the noise injection, remove the oscilloscope probe
sheath and wrap a nonshielded wire around the oscilloscope
probe. By keeping the ground lengths of the oscilloscope probe
as short as possible, the true ripple can be measured.
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