NCN5150_15 Datasheet, PDF (8/12 Pages) ON Semiconductor – Wired M-BUS Slave Transceiver

NCN5150
Table 9. TYPICAL BILL OF MATERIALS
Reference Designator
Value (Typical)
U₁
−
TVS₁
C_VDD
R_IS
C_SC
R_BUS1, R_BUS2
R_IDD
1 UL
2 UL
40 V
> 1 mF
100 W
220 nF
220 W
30 kW
13 kW
3 UL (Note 18)
8.45 kW
4 UL (Note 18)
6.19 kW
5 UL (Note 18)
4.87 kW
6 UL (Note 18)
4.02 kW
C_STC
1 UL
2 UL
≤ 330 mF
≤ 820 mF
3 UL (Note 18)
≤ 1,200 mF
4 UL (Note 18)
≤ 1,500 mF
5 UL (Note 18)
≤ 2,200 mF
6 UL (Note 18)
≤ 2,700 mF
18. 3−6 UL configurations are only possible for the NQFP variant.
Tolerance
−
−
−20%, +80%
1%
−20%, +80%
10%
1%
1%
1%
1%
1%
1%
10%
10%
10%
10%
10%
10%
Manufacturer
ON Semiconductor
ON Semiconductor
Part Number
NCN5150
1SMA40CAT3G
APPLICATION INFORMATION
The NCN5150 is a slave transceiver for use in the meter
bus (M-BUS) protocol. The bus connection is fully polarity
independent. The transceiver will translate the bus voltage
modulation from master-to-slave communication to TTL
UART communication, and in the other direction translate
UART voltage levels to bus current modulation. The
transceiver also integrates a voltage regulator for utilizing
the current drawn in this way from the bus, and an early
power fail warning. The transceiver also supports an
external power supply and the I/O high level can be set to
match the slave sensor circuit. A complete block diagram is
shown in Figure 2. Each section will be explained in more
detail below.
Meter Bus Protocol
M-BUS is a European standard for communication and
powering of utility meters and other sensors.
Communication from master to slave is achieved by
voltage-level signaling. The master will apply a nominal
+36 V to the bus in idle state, or when transmitting a logical
1 (“mark”). When transmitting a logical 0 (“space”), the
master will drop the bus voltage to a nominal +24 V.
Communication from the slave to the master is achieved
by current modulation. In idle mode or when transmitting a
logical 1 (“mark”), the slave will draw a fixed current from
the bus. When transmitting a logical 0 (“space”), the slave
will draw an extra nominal 15 mA from the bus. M-BUS
uses a half-duplex 11-bit UART frame format, with 1 start
bit, 8 data bits, 1 even parity bit, and a stop bit.
Communication speeds allowed by the M-BUS standard are
300, 600, 2400, 4800, 9600, 19200 and 38400 baud, all of
which are supported by the NCN5150.
Bus Connection and Rectification
The bus should be connected to the pins BUSL1 and
BUSL2 through series resistors to limit the current drawn
from the bus in case of failure (according to the M-BUS
standard). Typically, two 220 W resistors are used for this
purpose.
Since the M-BUS connection is polarity independent, the
NCN5150 will first rectify the bus voltage through an active
diode bridge.
Slave Power Supply (Bus Powered)
A slave device can be powered by the M-BUS or from an
external supply. The M-BUS standard requires the slave to
draw a fixed current from the bus. This is accomplished by
the constant current source CS1. This current is used to
charge the external storage capacitor C_STC. The current
drawn from the bus is defined by the programming resistor
R_IDD. The bus current can be chosen in increments of
1.5 mA called unit loads. Table 5 list the different values of
programming resistors needed for different unit loads, as
well as the current drawn from the bus (I_BUS) and the current
that can be drawn from the STC pin (I_STC). I_STC is slightly
less than I_BUS to account for the internal power consumption
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