Silicon Laboratories C8051F996-DK User Manual page 14

C8051F996-DK
7.2. Target Board Power Options and Current Measurement
(J10, J11, J17, H2, P2, P3, SW5)
The C8051F996 Target Board supports three power options, selectable by the three-way header (J10/J11). Power
to the MCU may be switched on/off using the power switch (SW5). The power options are described in the
paragraphs below.
7.2.1. Wall Power
When the J10/J11 three-way header is set to WALL_PWR, the C8051F996 Target Board may be powered from the
following power sources:
 9 VDC power using the ac to dc power adapter (P2)
 5 VDC USB VBUS power from PC via the USB Debug Adapter (J9)
 5 VDC USB VBUS power from PC via the CP2103 USB connector (P3)
All the three power sources are ORed together using reverse-biased diodes (D1, D2, D3), eliminating the need for
headers to choose between the sources. The target board will operate as long as any one of the power sources is
present. The ORed power is regulated to a 3.3 V dc voltage using a LDO regulator (U2). The output of the regulator
powers the +3 VD net on the target board. The VBAT supply net on the target board is powered directly from the
+3 VD net.
7.2.2. AAA Battery
When the J10/J11 three-way header is set to AAA_BAT, the C8051F996 Target Board is powered from the series
combination of the AAA batteries inserted in BH1 and BH2.
7.2.3. Coin Cell Battery
When the J10/J11 three-way header is set to COIN_CELL, the C8051F996 Target Board may be powered from a
3 V Lithium (CR2032) coin cell inserted in BH3.
7.2.4. Measuring Current
The header (J17) and terminal block (H2) provide a way to measure the total supply current flowing from the power
supply source to the MCU. The measured current does not include any current from the PWR LED (DS2) or the
quiescent current from the power supply; however, it does include the current used by any LEDs powered from the
VDD supply net or sourced through a GPIO pin. See the target board schematic in Figure 10 through Figure 12 for
additional information.
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Downloaded from Elcodis.com electronic components distributor
J11
COIN_CELL
PWR
AAA_BAT
WALL_PWR
J11
COIN_CELL
PWR
AAA_BAT
WALL_PWR
J11
COIN_CELL
PWR
AAA_BAT
WALL_PWR
Rev. 0.1