_______________Detailed Description
The MAX214 RS-232 transceiver provides a complete,
8-line, software-configurable, DTE or DCE port RS-232
interface. Tx, Rx, RTS, CTS, DTR, DSR, DCD, and RI
circuits can be configured as either Data Terminal
Equipment (DTE) or Data Circuit-Terminating
Equipment (DCE) using the DTE/DCE control pin. The
MAX214 eliminates the need to swap cables when
switching between DTE and DCE configurations. This
is useful when, for example, a portable computer is
required to communicate with printers, modems, and
other computers without carrying multiple cables.
The MAX214 runs from a single +5V supply and incor-
porates a dual charge-pump voltage converter to gener-
ate the necessary voltages for the RS-232 transmitters.
A shutdown mode is provided to save power when
transmission is not required, but the receivers always
stay active for simple detection of ring indicator signals.
DTE/DCE Operation
The DTE/DCE pin allows circuit configuration under
software control. Tables 1a and 1b show the pin defini-
tions of the MAX214 in both DTE and DCE modes. The
Function columns show the direction of data flow from
the input pin to the output pin of the MAX214, and onto
the corresponding DB-25 connector’s pin.
+5V to ±10V Dual Charge-Pump
Voltage Converter
The +5V to ±10V conversion is performed by two
charge-pump voltage converters (Figure 2). The first
uses capacitor C1 to double the +5V to +10V, storing
the +10V on the output filter capacitor, C3. The second
charge-pump voltage converter uses C2 to invert the
+10V to -10V, storing the -10V on the V- output filter
capacitor, C4.
In shutdown mode, V+ is pulled to V
CC
by an internal
resistor, and V- falls to GND.
MAX214
Programmable DTE/DCE,
+5V RS-232 Transceiver
_______________________________________________________________________________________ 5
PIN
14
NAME
V-
9, 18, 20 TRA, TRC, TRB
15 V+
7 RDC
6, 8, 22, 23 RA, RE, RC, RB
5, 24, 25 TA, TC, TB
16
10, 17, 19 RTA, RTC, RTB
11 RDTC
V
CC
21
12
DTE/DCE
RRE
13 GND
26 SHDN
27, 28
3
C1+, C1-
1, 2 C2+, C2-
HI-Z
4 N.C.
FUNCTION
-2V
CC
voltage generated by the charge pump
+2V
CC
voltage generated by the charge pump
TTL/CMOS receiver A, E, C, B outputs
TTL/CMOS driver A, C, B inputs
+4.5V to +5.5V supply voltage
RS-232 receiver input
Ground
Shutdown control; shutdown high, normal operation low
Terminals for positive charge-pump capacitor
Terminals for negative charge-pump capacitor
No connect—not internally connected
______________________________________________________________Pin Description
RS-232 receiver impedance control. Take high to disconnect the termination resistor.
TTL/CMOS DTE receiver output D for DTE/DCE = 0V, or TTL/CMOS DCE receiver output C for
DTE/DCE = +5V
RS-232 DTE receiver input for DTE/DCE = 0V, or RS-232 DCE driver output for DTE/DCE = +5V
RS-232 DTE receiver input D for DTE/DCE = 0V, or RS-232 DCE driver output C for
DTE/DCE = +5V
Data terminal equipment (DTE) and data circuit-terminating equipment (DCE) control pin.
DCE active high and DTE active low.
RS-232 DTE driver output for DTE/DCE= 0V, or RS-232 DCE receiver input for DTE/DCE = +5V
