1 µA S u p p ly Cu rre n t , 1 Mb p s , 3 .0 V t o 5 .5 V,
RS -2 3 2 Tra n s c e ive rs w it h Au t o S h u t d o w n P lu s
–7/MAX3245
P in De s c rip t io n
PIN
NAME
FUNCTION
MAX3224
MAX3225
MAX3226
MAX3227
MAX3244
MAX3245
Ready to Transmit Output, active high. READY is enabled high when
V- goes below -4V and the device is ready to transmit.
1
1
—
READY
2
2
3
28
27
C1+
V+
Positive Terminal of Voltage-Doubler Charge-Pump Capacitor
+5.5V generated by the charge pump
3
4
5
4
24
C1-
Negative Terminal of Voltage-Doubler Charge-Pump Capacitor
Positive Terminal of Inverting Charge-Pump Capacitor
Negative Terminal of Inverting Charge-Pump Capacitor
-5.5V generated by the charge pump
5
1
C2+
6
6
2
C2-
7
7
3
V-
8, 17
9, 16
10, 15
13
8
9–11
4–8
15–19
T_OUT
R_IN
R_OUT
RS-232 Transmitter Outputs
RS-232 Receiver Inputs
9
TTL/CMOS Receiver Outputs
Valid Signal Detector Output, active low. A logic high indicates that a valid
RS-232 level is present on a receiver input.
11
12, 13
14
10
11
12
21
12–14
23
INVALID
T_IN
TTL/CMOS Transmitter Inputs
Force-On Input, active high. Drive high to override AutoShutdown Plus,
keeping transmitters and receivers on (FORCEOFF must be high) (Table 1).
FORCEON
GND
18
19
14
15
25
26
Ground
V
CC
+3.0V to +5.5V Single Supply Voltage
Force-Off Input, active low. Drive low to shut down transmitters, receivers
(except R2OUTB), and charge pump. This overrides AutoShutdown Plus
and FORCEON (Table 1).
20
—
16
—
22
20
FORCEOFF
R2OUTB
TTL/CMOS Noninverting Complementary Receiver Outputs. Always active.
The READY output (MAX3224–MAX3227) is low when
the charge pumps are disabled in shutdown mode. The
READY signal asserts high when V- goes below -4V.
_______________De t a ile d De s c rip t io n
Du a l Ch a rg e -P u m p Vo lt a g e Co n ve rt e r
The MAX3224–MAX3227/MAX3244/MAX3245’s internal
p owe r s up p ly c ons is ts of a re g ula te d d ua l c ha rg e
pump that provides output voltages of +5.5V (doubling
charge pump) and -5.5V (inverting charge pump), over
the +3.0V to +5.5V range. The charge pump operates
in discontinuous mode: if the output voltages are less
than 5.5V, the charge pump is enabled; if the output
voltages exceed 5.5V, the charge-pump is disabled.
Each charge pump requires a flying capacitor (C1, C2)
and a reservoir capacitor (C3, C4) to generate the V+
and V- supplies.
RS -2 3 2 Tra n s m it t e rs
The tra ns mitte rs a re inve rting le ve l tra ns la tors tha t
convert CMOS-logic levels to 5.0V EIA/TIA-232 levels.
The MAX3224/MAX3226/MAX3244 g ua ra nte e a
250kbps data rate (1Mbps for the MAX3225/MAX3227/
MAX3245) with worst-case loads of 3kΩ in parallel with
1000pF, providing compatibility with PC-to-PC com-
munication software (such as LapLink™). Transmitters
can be paralleled to drive multiple receivers. Figure 1
shows a complete system connection.
LapLink is a trademark of Traveling Software.
_______________________________________________________________________________________
7
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
