DEMO MANUAL DC1880A
LTC2874
Quad IO-Link Master
Hot Swap Controller and PHY
Description
Demonstration circuit 1880A showcases the
LTC
®
2874,
a
quad Hot Swap™ controller and PHY suitable for IO-Link
®
master and other applications. DC1880A operates from
an external supply V
DD
and utilizes the DC590 USB serial
controller board to communicate with the LTC2874 using
SPI protocol.
Design files for this circuit board are available at
http://www.linear.com/demo/DC1880A
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and Hot
Swap, QuikEval and Linduino are trademarks of Linear Technology Corporation. IO-Link is
a registered trademark of PROFIBUS User Organization (PNO). All other trademarks are the
property of their respective owners.
performance summary
SYMBOL
V
DD
ΔV
ACL
PARAMETER
Input Supply Range
L+ Analog Current Limit Voltage
Specifications are at T
A
= 25°C, V
DD
= 24V, and V
L
= 3.3V.
MIN
8
20
9.2
42
16.7
50
100
13
1.2
1.1
±500
±110
±700
±160
±230
TYP
MAX
30
30
24.2
58
UNITS
V
V
mV
mV
mV
V
V
V
V
V
mA
mA
kb/s
kb/s
80
85
20
µs
MHz
CONDITIONS
24VMODE = 0
24VMODE = 1
ΔV
ACL
= V
SENSE+
– V
SENSE–
V
L+
= 0V, FLDBK_MODE = 1
V
L+
= V
DD
– 1V
Start-Up, 2XPTC Enabled, V
L+
> 18V
I
GATE
= –1µA
V
DD
= 17V to 30V
V
DD
= 8V
Output High, I
CQ
= –100mA
Output Low, I
CQ
= 100mA
ΔV
GATE
V
RQH
,
V
RQL
I
QPKH
,
I
QPKL
I
QH
, I
QL
f
DTR
t
WU
External N-Channel Gate Drive
(V
GATE
– V
L+
)
CQ Residual Voltage
Wake-Up Request (WURQ) Current
CQ Current Limit
Maximum Data Transfer Rate
10
4.5
15
15
1.6
1.5
f
DTR
= 4nF
SLEW = 0
SLEW = 1
50% Duty Cycle
38.4
230.4
75
WURQ Pulse Duration
SCK Frequency
dc1880af
1
DEMO MANUAL DC1880A
Quick start proceDure
Figure 1. Proper Setup
2
dc1880af
DEMO MANUAL DC1880A
Quick start proceDure
DC1880A is a 6-layer demonstration board. An LDO is
included to optionally derive the V
L
logic supply from
the V
DD
input supply. An LED lights up when the
IRQ
pin
signals interrupt requests.
1. Install, or update as needed, Linear Technology's
QuikEval™ evaluation software on the PC. See Using
the LTC2874 Software section for more information.
2. Connect the DC590 board to the PC with a standard
USB A/B cable.
3. Connect the DC1880A board to the DC590 board using
the 14-conductor ribbon cable supplied with the DC590
board.
4. Choose the source for the VL logic supply—the DC590,
the LDO on the DC1880A, or either if both are set to
the same voltage:
a. Set the DC1880A LDO jumpers (JP11 and JP12) and
DC590 VCCIO jumper (JP6) to one of the combina-
tions listed in Table 1. Default jumper positions set
both boards to 5V.
b. When using a Linduino™ One instead of a DC590
board, set the DC1880A LDO to 5V (JP11 = 5.0V)
or disable it (JP12 = OPEN).
5. Before connecting the input power supply to the
DC1880A board, verify the voltage is below 40V
(normally between 8V and 30V) and that the supply
is turned off.
6. Connect the power supply between V
DD
and GND on
the DC1880A board as shown in Figure 1.
7. Connect line interface cables (up to 20m long) to either
the screw-terminal blocks (J1-J4) or the IO-Link con-
nectors (J5-J8).
8. Turn on the 24V power supply and verify that the
IRQ
LED on the DC1880A board is lit. (The LTC2874 is
signalling that one or more of its supplies had been
low.)
9. Launch the GUI software. Refer to the Using the
LTC2874 Software section for more information on
how to control the LTC2874 using the GUI.
10. Clear the
IRQ
condition by clearing any Supply Event
bits that are set. On the Events tab, simply click on any
lamps that are lit.
11. Refer to the Additional Information section and the
data sheet for operating details.
dc1880af
3
DEMO MANUAL DC1880A
aDDitional information
VL Logic Supply
Table 1 lists several ways to supply power to the VL pin.
Methods 1a/b/c are recommended for most purposes.
Table 1. Recommended Options for Powering the VL Supply
METHOD
1a
1b
1c
2
3
4
DC590
JP6
5V*
3.3V
OPEN (2.7V)
EXT
EXT
5V* or 3.3V
DC1880A
JP12
ON*
ON*
ON*
ON*
OPEN
OPEN
DC1880A
JP11
5V*
3.3V
OPEN (2.9V)
X**
X**
X**
SOURCE FOR
VL POWER
LDO or DC590
LDO or DC590
LDO or DC590
LDO
DC1880A VL TURRET
DC590
Table 3. CQ Driver Output Level Configuration
JP2/4/8/10
SETTING
GND
GND/VL
EXT
DB9
TXD
TURRET
X
X
L/H
X
DRVEN
BIT
X
X
X
H/L**
CQ DRIVER
MODE*
OFF
ON
ON
ON
CQ
LEVEL
L
H/L
H/L
H/L
* From Table 2
** RS232 transceiver U2 inverts
Alternatively, operate the CQ drivers solely via the SPI
interface by tying TXD low and controlling the DRVEN
register bits. This method is suitable for SIO mode and
switching at or below COM2 data rates (38.4kb/s).
TVS Protection
The CQ and L+ pins are protected by 36V TVS diodes for
cable-driving applications.
Serial Port
A DB9 connector enables CQ data to be sent (for one or
more ports) and received (for one port) using PC software
such as a serial terminal program. Jumper JP5 enables
the required RS-232 transceiver.
Select the desired combination of drivers by setting one
or more of JP2/4/8/10 to the DB9 position. Select one CQ
receiver using JP6.
L+ Isolation
If L+ isolation is not needed, Schottky diodes D1-D4 may
be replaced with 0Ω resistors.
Interrupts
The LTC2874 includes an open-drain interrupt line for
signaling the host controller when it needs service. This
signal is accessible on the DC1880A board at the
IRQ
test
point. An LED is also included for convenience.
* (Default)
** Including OPEN (2.9V)
L+ Power Supply Outputs
Enable the L+ power supply outputs by setting their
respective EN_L+ register bits high.
CQ Line Driver Outputs
Enable the CQ line drivers either by input pin (using the
TXEN turrets and/or jumpers JP1/3/7/9) or via the SPI
interface (by setting DRVEN register bits high). See Table 2.
Table 2. CQ Driver Mode Configuration
JP1/3/7/9
SETTING
GND
VL
X
EXT
TXEN
TURRET
X
X
X
L/H
DRVEN
BIT
0
X
1
0
CQ DRIVER
MODE
OFF
ON
ON
OFF/ON
Control the output CQ states using the TXD turrets and/
or jumpers JP2/4/8/10. See Table 3.
4
dc1880af
DEMO MANUAL DC1880A
aDDitional information
Jumpers
JP1/3/7/9:
Port 4/3/2/1 CQ Driver Enables. See Table 2.
Default position VL.
JP2/4/8/10:
Port 4/3/2/1 Data Input to CQ Driver. See
Table 3. Default position GND.
JP6:
RXDn COM Port Select. Determines which receiver
output (RXD1/2/3/4, if any) is connected to the serial port.
Default position RXD1.
JP5:
COM PORT Enable. Connects RS232 transceiver U2
to VL logic supply. Default position ON.
JP11:
VL Select. Programs LDO voltage to 2.9V (OPEN),
3.3V, 5V, or 5.5V. Default position 5V.
JP12:
LDO On. Enables LDO which derives VL logic sup-
ply from V
DD
supply voltage input. Default position ON.
JP13:
GND Shield. Shorts shields of J5-8 to GND. Default
position OPEN.
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