Linear Technology LTC6804-1 - 4-Wire Serial Peripheral Interface (SPI) Physical Layer; 2-Wire Isolated Interface (Isospi) Physical Layer

LTC6804-1/LTC6804-2
36
680412fc
For more information www.linear.com/LTC6804-1
Figure 14. 4-Wire SPI Configuration
DAISY-CHAIN SUPPORT
680412 F14
V
+
C12
S12
C11
S11
C10
S10
C9
S9
C8
S8
C7
S7
C6
S6
C5
S5
C4
S4
C3
S3
C2
S2
C1
MISO
MOSI
CLK
CS
V
DD
MPU
IPB
IMB
ICMP
IBIAS
SDO (NC)
SDI (NC)
SCK (IPA)
CSB (IMA)
ISOMD
WDT
DRIVE
V
REG
SWTEN
V
REF1
V
REF2
GPIO5
GPIO4
V
–
V
–
GPIO3
GPIO2
GPIO1
C0
S1
LTC6804-1
ADDRESS PINS
5k 5k
V
+
C12
S12
C11
S11
C10
S10
C9
S9
C8
S8
C7
S7
C6
S6
C5
S5
C4
S4
C3
S3
C2
S2
C1
MISO
MOSI
CLK
CS
V
DD
MPU
A3
A2
A1
A0
SDO (IBIAS)
SDI (ICMP)
SCK (IPA)
CSB (IMA)
ISOMD
WDT
DRIVE
V
REG
SWTEN
V
REF1
V
REF2
GPIO5
GPIO4
V
–
V
–
GPIO3
GPIO2
GPIO1
C0
S1
LTC6804-2
operaTion
4-WIRE SERIAL PERIPHERAL INTERFACE (SPI)
PHYSICAL LAYER
External Connections
Connecting ISOMD to V
–
configures serial Port A for
4-wire SPI. The SDO pin is an open drain output which
requires a pull-up resistor tied to the appropriate supply
voltage (Figure14).
Timing
The 4-wire serial port is configured to operate in a SPI
system using CPHA = 1 and CPOL = 1. Consequently, data
on SDI must be stable during the rising edge of SCK. The
timing is depicted in Figure 15. The maximum data rate
is 1Mbps.
2-WIRE ISOLATED INTERFACE (isoSPI) PHYSICAL
LAYER
The 2-wire interface provides a means to interconnect
LTC6804 devices using simple twisted pair cabling. The
interface is designed for low packet error rates when the
cabling is subjected to high RF fields. Isolation is achieved
through an external transformer.
Standard SPI signals are encoded into differential pulses.
The strength of the transmission pulse and the threshold
level of the receiver are set by two external resistors, R
B1
and R
B2
. The values of the resistors allow the user to trade
off power dissipation for noise immunity.