SM3320 Datasheet, PDF (1/8 Pages) National Semiconductor (TI) – Reference Design integrates power optimizer and a low-cost 2.4GHz

SM3320-RF-EV Reference
Design
National Semiconductor
Application Note 2122
Arief Hernadi
February 17, 2011
Introduction
The SolarMagic™ SM3320-RF-EV reference design inte-
grates a power optimizer and a low-cost 2.4GHz radio to add
a remote shutdown feature to a PV system. The remote shut-
down feature can be used during installation, maintenance,
or emergency situations to de-energize the PV system.
Although its principal purpose is to communicate shutdown
intent, this RF system is 2-way and can be used for a wide
variety of communication applications, including monitoring,
security and identification.
The SolarMagic™ SM3320-RF-EV is based off of the
SM3320-1A1 power optimizer, and shares all of its best-in-
class power optimization features. This includes its ability to
mitigate real-world mismatch, its 99.5% peak efficiency, and
its Panel-Mode operation. In addition, the same ultra-low pro-
file form factor of the original SM3320-1A1 is maintained so
that it can be integrated into the same junction box designs.
This evaluation board should work as a power optimizer even
without a transmitter
The wireless RF communications in the SM3320-RF-EV is
implemented using a low-cost Nordic nRF24LE1 chip. This is
a low-cost, 2.4GHz radio and 8051 microcontroller on a single
chip. The 2.4GHz radio uses narrow band modulation (as op-
posed to direct sequence spread spectrum), which can be
used either with or without frequency hopping. Example soft-
ware is provided that implements the remote shutdown fea-
ture on the 8051 microcontroller in the nRF24LE1.
One of the unique features of the SM3320-RF-EV is its use
of the DC power lines as an RF antenna and transmission
line. This enables the SM3320-RF-EV to maintain radio com-
munication even when it is mounted in the junction box of the
module. This antenna design can be used with other 2.4GHz
radio chipsets besides the nRF24LE1 by straightforward
modification of the provided design files.
The SM3320-RF-EV reference design provides a flexible plat-
form for developing value added features in firmware with no
additional hardware development. Examples of these fea-
tures include module-level monitoring, security (theft-detec-
tion and theft-deterrence), and identification. Similarly,
firmware development on this platform can be used to cus-
tomize the SM3320-RF-EV to be compatible with an existing
monitoring system or inverter communication protocol if a
customer desires.
SolarMagic™ technology is an overall solution that works in
existing and new installations, residential, commercial, and
utility scale projects. National Semiconductor’s 50 years of
experience in the electronics industry delivers unsurpassed
manufacturing, design, and development technology.
System Overview
Figure 1 depicts how the SM3320-RF-EV design would be
implemented in its intended application. In this example, ev-
ery module is connected to an SM3320-RF-EV power opti-
mizer. Under normal conditions, the central transmitter sends
a signal to each SM3320-RF-EV power optimizer indicating
that it is ok to operate and output power. When an emergency
condition occurs, the central transmitter will send a signal
command to all the SM3320-RF-EV to shutdown. This de-
energizes the output of each SM3320-RF-EV, and in doing so
brings down the voltage of the DC bus and all DC wiring to a
safe voltage level.
30143801
FIGURE 1. System Overview Showing Intended Application of SM3320-RF-EV Board in a PV System
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