NXP Semiconductors QN9080-001-M17 DK, Руководство пользователя, Страница: 11 / 27

NXP Semiconductors
UM11184
QN9080-001-M17
DK User’s Guide
UM11184 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2019. All rights reserved.
User Manual Rev. 0
— January 2019
11 of 27
On the QN9080SIP module board, remove the jumper on J1 and short Pin1 and Pin2 of
the J2 to measure the QN9080 current draw only.
3.2.1 Current test using LPC4322
The QN9080-001-M17 DK board has an on-board current measurement circuit consisting
of the MAX9634T (U18) current monitor chip and the 12-bit ADC (ADC122S021, U19)
with 12-bit sampling from 50 ksps to 200 ksps. The on-board MAX9634T current monitor
measures the voltage across the QN9080-001-M17 VCC V-sense resistors; either 8.24
Ω
or 4.12
Ω if JP13 is installed. MAX9634 multiplies the sense voltage 25 times to provide a
voltage range suitable for the ADC to measure.
A 2-input analog mux is used to select the channel to be measured; either the
QN9080-001-M17 or the devices from the expansion board on the DK extension
connectors. The current measurement circuit is controlled by the Link2 processor and is
not user-programmable. The power-measurement utilities with this feature are available
only after installing the MCUXpresso IDE.
Due to the input offset voltage variations in MAX9634, the current-measurement circuit is
not recommended for measuring currents below 150

A.
The QN9080-001-M17 current can be measured by the voltage across a sense resistor
in series with the supply. The voltage across a series 4.12-
Ω resistor with the target
QN9080-001-M17 VCC can be manually measured at JP12 on the PCB. Use the
Ohm’s
law to calculate the current (QN9080-001-M17 current = measured voltage / 4.12
Ω). For
example, if the measured voltage is 10 mV, then 10e-3 / 4.12
Ω = 2.44 mA. Note that the
current consumed by MAX9634 used in the on-board current measurement is included in
the voltage measured on this resistor. The detailed schematic is shown in
Fig 14 .
Fig 14. Current test using the LPC processor
When performing the current test using the Link2 processor, jumpers JP12, JP13, and
JP14 must be set according to
Table 8 .
Table 8. Current test jumper setting
JP12 Open when used for the Link2 processor current test.
JP13 Open when used for the Link2 processor current test.
JP14 Short when no digital ammeter in series.