Data Sheet

5.3 Power States and Low-Power Modes
The current consumption on WFM200S is highly dynamic. It varies significantly depending on its activity, the activation of power-save
modes, and when it is in shutdown.
There are four main modes, each of them having several power states as detailed below.
Traffic mode: The Traffic mode is defined as the mode when WFM200S is transmitting data, receiving data, or listening to the channel.
If power save is not activated, the device stays in listen mode when there is no traffic. Current consumption is similar between receive
and listen modes, while it is higher during transmission.
Power save modes: When power save mode is activated, the device goes to a low-consumption mode and wakes-up periodically to
listen to network beacons, so the device stays associated to the network. The current consumption, while receiving beacons, is as
mentioned above for reception.
There are three power-save/low-power consumption cases:
1. Sleep: If a 32 KHz clock is available at LP_CLK input, then the device goes in sleep mode between reception of beacons. In this
mode, most of the chip is turned off (including Xtal oscillator and host interface) to reduce the power consumption as much as
possible. Given that the host interface is shut down in this mode, the host should assert the WUP pin to wake up the device before
any communication with the host can be achieved.
2. Sleep with XO on: If low-power clock is not available on LP_CLK or if the Xtal oscillator cannot be shut down, then the device goes
in "Sleep with XO on" mode between reception of beacons. In this mode, the Xtal oscillator is active, so the typical consumption is
higher.
3. Snooze: If low-power clock is not available on LP_CLK then the device goes in snooze mode between reception of beacons. In this
mode, a smaller part of the device is shut down and the XO is always enabled, so the typical consumption is higher.
The sleep or snooze state/mode can also be achieved when not associated if the firmware decides there are no tasks to perform when
the wake-up signal (pin GPIO/WUP) from host is low.
Shutdown mode: Shutdown mode is the case where the transceiver is shut down and reaches the lowest power consumption while
still being connected to the power supplies. Getting out of stand-by requires a complete start-up sequence triggered by RESETn pin
being set from low to high.
Reset mode:When RESETn is low, the consumption is typically 76 µA, mainly due to the RESETn pull-up resistor within the device.
5.4 RF Connections
5.4.1 RF Ports
This device has two RF ports to allow antenna diversity using an internal switch. In applications with only one antenna, the un-used port
should be terminated to ground through a resistor between 47 to 51 Ω.
5.4.2 Antenna Diversity
In Applications where the main antenna is subject to obstruction or de-tuning, a second antenna can be attached to the alternate RF
port by using the diversity antenna switch. The location of this second antenna should be such that both cannot be prevented from
operating satisfactorily by the same event. A firmware feature can be invoked to determine which antenna has a better path to the re-
mote Wi-Fi Device.
5.4.3 Embedded Antenna Pins
For OPNs with embedded antenna, pin 2 (2G4ANT_IN) is the antenna input port. This has a reference impedance of 50 Ohms on nomi-
nal size host boards. The pin 3 (RF_1 port) is coupled to pin 2 when using the embedded antenna. Pin 47 is an intermediate connection
to a loop trace on the host board. Follow UG395 for required dimensions of this trace when using the embedded antenna. When not
using the embedded antenna, pin 2 and pin 47 are left floating. For OPNs without embedded antenna, pin 2 and pin 47 are disconnec-
ted internally.
5.5 Clocks
5.5.1 High Frequency Crystal Oscillator
WFM200S has an internal 38.4MHz crystal used with the integrated oscillator circuitry to provide High Frequency Crystal Oscillator as
the internal reference clock. A proprietary technique is used to calibrate and compensate for frequency errors. This achieves a frequen-
cy stability of +/-20ppm over the operating temperature range.
WFM200S Data Sheet
Typical Applications and Connections
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