PPK2 Insertion Impedance

[JLThompson]

What is the insertion impedance when using the PPK2 to monitor power consumption? My project uses a CR2450 battery and runs fine directly from that power source. It also runs fine using the PPK2 to supply power. But when I use the PPK2 to monitor the power my project draws from its battery, the project will not boot up and the PPK2 shows a sequence of current pulses that hit a peak, then rapidly decay.

[Kazi Afroza Sultana]

Hello,

How have you wire the PPK2 to the DUT (Device under Test)?

[JLThompson]

Battery+ to PPK2 red wire, PPK2 brown wire to DUT VBAT+, PPK2 black wire to DUT GND.

[Kazi Afroza Sultana]

Could you please show me the setup picture? I am sorry that I can not get clear picture form the reply.

The PPK2 is designed to measure current on the high side (between battery positive and device VCC), not in the ground path. Incorrect wiring can cause measurement errors or device malfunction. Ensure VIN is connected to battery plus, VOUT to your board's VCC, and GND to board ground if you measure in ampere meter mode. From your reply it seems Ampere mode.

I also want to see the set up on the application side on the power profiler app. 

[hmolesworth]

Maybe try forcing the PPK2 to a less sensitive range, as the range-switch on the PPK2 is slowish. I made these notes some time ago to show the range series impedance. To test simply place a bypass resistor across the DUT which will force the PPK2 to be in low-impedance mode before the DUT is connected; if it boots ok then this is probably the issue.

// note the resistor (labelled DUT) must connect to the PPK-II Gnd and not just the battery negative.
// The PPK-II is not a 2-wire current meter but a 3-terminal voltage monitor which reads the voltage
// across the internal series resistor RC where Rc is used for current sense
// Resistor Rc for current sense is 1k0 in parallel with none or more of 110R, 11R0, 1R0 and 0R051
//
//              <- +ve Supply to DUT From VOUT                               External Battery +ve To VIN
//             +------------------------------+                             +-----------------------+
//             |                              |                             |                       |
//             |              +---------+     |                             |     +---------+       |
//             |              |     GND |     | VOUT                   VIN  |     | GND -ve |       | CR2450
//   +=========O=========+    |    +====O=====O=============================O=====O====+    |       | Battery
//   |        Vdd (+)    |    |    |    |     #----+                        |     |    |    |       | + 3 volts
//   |                   |    |    |    |     |    |Rc        AMPERE \      |     |    |    |     +-O-+
//   |                   |    |    |    |     |   +++                 \     |     |    |    |     |   |
//   |                   |    |    |    |     |   | |   +-----------O  O----#     |    |    |     |   |
//   | Device Under Test |    |    |    |     |   | |   |                   |     |    |    |     |   |
//   |       DUT         |    |    |    | 120k|   | |   |                   |120k |    |    |     |   |
//   |                   |    |    |    |    +++  +++   |   \  SOURCE      +++    |    |    |     |   |
//   |                   |    |    |    |    | |   |    |    \             | |    |    |    |     +-O-+
//   |                   |    |    |    |    | |   +----#--O  O-- PPK LDO  | |    |    |    |       | Gnd (-)
//   |                   |    |    |    |    | |                           | |    |    |    +-------+
//   |                   |    |    |    |    +++                           +++    |    |
//   |                   |    |    |    |     |                             |     |    |
//   |                   |    |    |    |     #-- VDUT                VIN --#     |    |
//   |                   |    |    |    |     |  Sense                Sense |     |    |
//   |                   |    |    |    |    +++                           +++    |    |
//   |                   |    |    |    |    | |                           | |    |    |
//   |                   |    |    |    |    | |                           | |    |    |
//   |                   |    |    |    |    | |                           | |    |    |
//   |                   |    |    |    |    +++                           +++    |    |
//   |                   |    |    |    |     | 30k                     30k |     |    |
//   |                   |    |    |    +--#--+                             +--#--+    |
//   |                   |    |    |       |                                   |       |
//   |                   |    |    |     =====      <<== Common Gnd ==>>     =====     |
//   |                   |    |    |      ===           (Common -ve)          ===      |
//   |        Gnd (-)    |    |    |       =                                   =       |
//   +=========O=========+    |    +===================================================+
//             |              |     PPK-II
//             +--------------+

[JLThompson]

I was trying to use the PPK2 as a simple ammeter in series with the battery, a 2-wire connection.. I didn’t realize I needed to use all 4 wires. Now it works! Thanks!!