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MAX220–MAX249
+5V-Powered, Multichannel
RS-232 Drivers/Receivers
Tables 1a–1d define the control states. The MAX244
has no control pins and is not included in these tables.
The MAX246 has ten receivers and eight drivers with
two control pins, each controlling one side of the
device. A logic high at the A-side control input (ENA)
causes the four A-side receivers and drivers to go into
a three-state mode. Similarly, the B-side control input
(ENB) causes the four B-side drivers and receivers to
go into a three-state mode. As in the MAX245, one A-
side and one B-side receiver (RA5 and RB5) remain
active at all times. The entire device is put into shut-
down mode when both the A and B sides are disabled
(ENA = ENB = +5V).
The MAX247 provides nine receivers and eight drivers
with four control pins. The ENRA and ENRB receiver
enable inputs each control four receiver outputs. The
ENTA and ENTB transmitter enable inputs each control
four drivers. The ninth receiver (RB5) is always active.
The device enters shutdown mode with a logic high on
both ENTA and ENTB.
The MAX248 provides eight receivers and eight drivers
with four control pins. The ENRA and ENRB receiver
enable inputs each control four receiver outputs. The
ENTA and ENTB transmitter enable inputs control four
drivers each. This part does not have an always-active
receiver. The device enters shutdown mode and trans-
mitters go into a three-state mode with a logic high on
both ENTA and ENTB.
The MAX249 provides ten receivers and six drivers with
four control pins. The ENRA and ENRB receiver enable
inputs each control five receiver outputs. The ENTA
and ENTB transmitter enable inputs control three dri-
vers each. There is no always-active receiver. The
device enters shutdown mode and transmitters go into
a three-state mode with a logic high on both ENTA and
ENTB. In shutdown mode, active receivers operate in a
low-power receive mode at data rates up to 20kb/s.
Applications Information
Figures 5 through 25 show pin configurations and typi-
cal operating circuits. In applications that are sensitive
to power-supply noise, V
CC
should be decoupled to
ground with a capacitor of the same value as C1 and
C2 connected as close as possible to the device.
