LTC2872
pin FuncTions
V
(Pins 1, 21, 31): Input Supply (3.0V to 5.5V). Tie all
DY2(Pin25):RS485DifferentialDriver#2InputorRS232
CC
three pins together and connect 2.2µF capacitor between
Driver #2y Input.
VCC and GND.
DZ1 (Pin 8): RS232 Driver #±z Input.
DZ2 (Pin 24): RS232 Driver #2z Input.
V (Pin 35): Logic Supply (±.7V to 5.5V) for the receiver
L
outputs, driver inputs, and control inputs. This pin should
Y1 (Pin 4): RS485 Differential Driver #± Positive Output
or RS232 Driver #±y Output, RS485 Differential Receiver
#± Positive Input (Half-Duplex Mode).
be bypassed to GND with a 0.±µF capacitor if it is not tied
to V . V must be less than or equal to V for proper
CC
L
CC
operation.
Y2 (Pin 28): RS485 Differential Driver #2 Positive Output
or RS232 Driver #2y Output, RS485 Differential Receiver
#2 Positive Input (Half-Duplex Mode).
V
(Pin20):GeneratedPositiveSupplyVoltageforRS232
DD
Driver(7V).Connect2.2µFcapacitorbetweenV andGND.
DD
V (Pin39):GeneratedNegativeSupplyVoltageforRS232
EE
Z1 (Pin 6): RS485 Differential Driver #± Negative Output
or RS232 Driver #±z Output, RS485 Differential Receiver
#± Negative Input (Half-Duplex Mode).
Driver (–6.3V). Tie all pins together and connect 2.2µF
capacitor between V and GND.
EE
GND(Pins5,18,27,34):Ground.Tieallfourpinstogether.
Z2 (Pin 26): RS485 Differential Driver #2 Negative Output
or RS232 Driver #2z Output, RS485 Differential Receiver
#2 Negative Input (Half-Duplex Mode).
CAP(Pin17):ChargePumpCapacitorforGeneratedNega-
tive Supply Voltage. Connect a 470nF capacitor between
CAP and SW.
485/232_1 (Pin 13): Interface Select #± Input. A logic low
enables RS232 mode and a high enables RS485 mode for
transceiver #±. The mode determines which transceiver
inputs and outputs are accessible at the LTC2872 pins
as well as which is controlled by the driver and receiver
enable pins.
SW (Pin 19): Switch Pin. Connect 22µH inductor between
SW and V .
CC
A1 (Pin 2): RS485 Differential Receiver #± Positive Input
(Full-Duplex Mode) or RS232 Receiver #±a Input.
A2 (Pin 30): RS485 Differential Receiver #2 Positive Input
(Full-Duplex Mode) or RS232 Receiver #2a Input.
485/232_2 (Pin 14): Interface Select #2 Input. A logic low
enables RS232 mode and a high enables RS485 mode for
transceiver #2. The mode determines which transceiver
inputs and outputs are accessible at the LTC2872 pins
as well as which is controlled by the driver and receiver
enable pins.
B1 (PIn 3): RS485 Differential Receiver #± Negative Input
(Full-Duplex Mode) or RS232 Receiver #±b Input.
B2(Pin29):RS485DifferentialReceiver#±NegativeInput
(Full-Duplex Mode) or RS232 Receiver #2b Input.
RA1 (Pin 37): RS485 Differential Receiver #± Output or
RXEN1 (Pin 9): Receivers #± Enable. A logic high disables
RS232andRS485receiversintransceiver#±,leavingtheir
outputs Hi-Z. A logic low enables the RS232 or RS485
receivers in transceiver #±, depending on the state of the
Interface Select Input 485/232_±.
RS232 Receiver #±a Output.
RA2 (Pin 33): RS485 Differential Receiver #2 Output or
RS232 Receiver #2a Output.
RB1 (Pin 38): RS232 Receiver #±b Output.
RB2 (Pin 32): RS232 Receiver #2b Output.
RXEN2(Pin23):Receivers#2Enable.Alogichighdisables
RS232andRS485receiversintransceiver#2,leavingtheir
outputs Hi-Z. A logic low enables the RS232 or RS485
receivers in transceiver #2, depending on the state of the
Interface Select Input 485/232_2.
DY1 (Pin 7): RS485 Differential Driver #± Input or RS232
Driver #±y Input.
2872f
8
Linear Systems [ Linear Systems ]
