Specifications
PL 3120/PL 3150/PL 3170 Power Line Smart Transceiver Data Book 157
Once enabled, the power management system detects any instance where the V
A
supply drops below the Smart
Transceiver’s lower power management threshold (nominally 7.9V). The PL Smart Transceiver then delays
transmission until the energy storage capacitor has been recharged, to allow transmission of a complete packet. The
PL Smart Transceiver then transmits any waiting packets once the capacitor has fully charged.
If a high packet transmission duty cycle causes V
A
to drop too low during packet transmission, then the packet is
aborted prior to completion. The PL Smart Transceiver will re-transmit that packet independent of the LonTalk
protocol service in use. Even when unacknowledged service is employed, a packet that is interrupted by low supply
voltage will be re-transmitted once the power management system determines that the supply is fully recharged.
The power management circuitry of the PL Smart Transceiver adjusts the amount of time that it inhibits transmission
based on the actual recharge characteristics of the device. A properly designed energy storage device will typically
transmit without intervention by the power management circuitry. When a device powered by an energy storage
supply has worst case component tolerances and is exposed to worst case AC line conditions, such that a packet must
be aborted and retransmitted, the power management circuitry of the Smart Transceiver calculates a suitable transmit
hold-off time by measuring the supply recharge rate. The formula used to make this calculation is three times the
time required for the supply to charge from its lower power management threshold (nominally 7.9V) to its upper
power management threshold (nominally 12.1V). Figure 5.1 illustrates examples of an energy storage node operating
under both typical and worst case conditions.
Figure 5.1 Supply Voltage vs. Packet Transmission
Transmission
Abor t
Packet
Retransmit
15
10
5
0
V
A
(Volts)
Tx
Packets
Typical Conditions
Worst Case Conditions