EVK-M8GZOE User Guide
UBX-16030132 - R04
Device description
Page 10 of 30
Early Production Information
4
Device description
4.1
Power supply (ZOE-M8G only)
5V main power supply
The EVK-M8GZOE board must be supplied either by the micro USB connector or by an external 4.5 V
– 5.5 V power supply connected to digital connector pin 2 and GND to pin 18. See Figure 1.
The interface circuitry and other logic on the board relies on the 5 V power supply to always work
properly.
In the default setup, this 5 V main power supply is connected to the low-dropout linear voltage
regulators (LDOs) that provide the 1.8 V
VCC
voltage of ZOE-M8G.
Power consumption of a ZOE-M8G based design can be easily calculated by measuring the voltage
drop over the
VCC
current measurement shunt resistor and then multiplying the resulting values by
the 1.8 V power supply voltage. For more information about current measurement of ZOE-M8G, see
section 5.1.
Backup power supply
The backup supply (
V_BCKP
) of ZOE-M8G is used to supply the ZOE-M8G and the optional RTC
crystal during hardware backup mode (main supply removed). This enables hot start and warm start
capabilities.
The EVK-M8GZOE includes a super capacitor to supply the V_BCKP of ZOE-M8G.
In normal operation, when the main supply of ZOE-M8G (VCC) is present, the backup domain in
ZOE-M8G is supplied by the main supply. V_BCKP supplies the backup domain of ZOE-M8G only
when the main supply
VCC
is removed.
4.1.2.1
Super capacitor
The capacity of the super capacitor is 1 F and provides backup power over a 100 Ω shunt resistor to
the ZOE-M8G (
V_BCKP
). When this 1 F capacitor is fully charged to 3.3 V, it can provide backup
power for about 35 hours (t=C*U/I=1*(3.3-1.4)/15uA=126,666 sec. -> ~35 hours).
As soon as the EVK-M8GZOE is supplied, the super capacitor gets charged.
When evaluating very long backup periods, the backup supply can be supplied by the digital
connector J1 pin 1 (2.5 V…3.6 V).
4.2
Interfaces
The EVK-M8GZOE supports all three communication interfaces of ZOE-M8G and ZOE-M8Q: UART,
DDC(I
2
C) and SPI.
Although the ZOE-M8 modules do not have a USB interface, there is a USB to UART converter on
EVK-M8GZOE that allows communication to ZOE-M8G by USB.
The UART interface of ZOE-M8G is available on USB, RS232 and on digital connector J1. Only use
one of them to communicate.
The SPI and the DDC (I
2
C) interface are only supported on digital connector J1, see section 4.4.
