IC-MHM Datasheet, PDF (36/63 Pages) IC-Haus GmbH – 14-BIT ABSOLUTE ANGLE HALL ENCODER

iC-MHM
14-BIT ABSOLUTE ANGLE HALL ENCODER
SERIAL INTERFACE: General
Rev D1, Page 36/63
The iC-MHM contains a serial interface that can be con-
figured to use differential RS422, single-ended TTL, or
LVDS (Low Voltage Differential Signaling) signal levels
as shown in Table 60.
RTX_MODE
Addr. 0x03; bit 4:3
Value
Input Levels
Output Levels
0
TTL (Single-ended)
RS422 (Differential)
1
TTL (Single-ended)
TTL (Single-ended)
2
LVDS (Differential)
LVDS (Differential)
3
RS422 (Differential)
RS422 (Differential)
Table 60: Serial Interface Configuration
TTL I/O is single-ended. This means that if
RTX_MODE = 0, pins NMA and NSLI are not used
and should be left unconnected. If RTX_MODE = 1,
pins NMAO, NMA, NSLI, and NSLO are not used and
should be left unconnected. LVDS and RS422 I/O are
differential and thus all serial interface pins are used.
With RS422 inputs (RTX_MODE = 3, the slave inputs
(pins SLI and NSLI) require external biasing resistors
as shown in Figure 20.
iC-MHM
SERIAL
INTERFACE
MAO
NMAO
MA
NMA
SLO
NSLO
SLI ='0'
to iC-MHM
internal
circuitry
-
NSLI
+
SLI
R3
NSLI
R2
BiSS chain
option
SLI
R1
Figure 20: Required External Biasing for RS422 In-
put Levels
In general, R1 = R3 ≤ (0.5 ∗ R2 ∗ (VDD/Vt()diff − 1)).
With TTL level inputs (RTX_MODE = 0 or 1), the slave
input (pin SLI) has an internal pull-down resistor of
50 kΩ (Elec. Char. item no. 902). An external pul-
l-down resistor (R1) with a value between 10 kΩ and
50 kΩ, as shown in Figure 19, may be necessary in
noisy environments.
iC-MHM
SERIAL
INTERFACE
MAO
NMAO
MA
NMA
SLO
NSLO
SLI ='0'
to iC-MHM
internal
circuitry
-
NSLI _{not used in TTL Mode}
+
SLI
SLI
R1
For example, if VDD = 4.5 V (worst case) and Vt()diff =
300 mV (Elec. Char. item no. 929), and R2 = 120 Ω,
then R1 = R3 ≤ 840Ω.
If an error occurs during startup, the serial interface
configuration defaults to TTL inputs and RS422 outputs
(RTX_MODE = 0). Refer to STARTUP AND OPERA-
TION on page 57 for more information.
The required configuration for SPI communication
with the iC-Haus MB3U-I²C Adapter is TTL inputs
(RTX_MODE = 0 or 1).
The serial interface must be configured to use the BiSS,
SSI, or SPI protocol as detailed in the following sec-
tions.
Figure 19: Optional External Pull-down Resistor for
TTL Input Levels