Datasheet
_______________Detailed Description
Dual Charge-Pump Voltage Converter
The MAX3224–MAX3227/MAX3244/MAX3245’s internal
power supply consists of a regulated dual charge
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.
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.
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
Pin Description
PIN
MAX3224
MAX3225
PDIP/
SSIP/
TSSOP
TQFN-
EP
MAX3226
MAX3227
MAX3244
MAX3245
NAME FUNCTION
1 19 1 — READY
Ready to Transmit Output, Active High. READY is enabled high when
V- goes below -4V and the device is ready to transmit.
2 1 2 28 C1+ Positive Terminal of Voltage-Doubler Charge-Pump Capacitor
3 20 3 27 V+ +5.5V Generated By the Charge Pump
4 2 4 24 C1- Negative Terminal of Voltage-Doubler Charge-Pump Capacitor
5 3 5 1 C2+ Positive Terminal of Inverting Charge-Pump Capacitor
6 4 6 2 C2- Negative Terminal of Inverting Charge-Pump Capacitor
7 5 7 3 V- -5.5V Generated By the Charge Pump
8, 17 6, 15 13 9, 10, 11 T_OUT RS-232 Transmitter Outputs
9, 16 7, 14 8 4–8 R_IN RS-232 Receiver Inputs
10, 15 8, 13 9 15–19 R_OUT TTL/CMOS Receiver Outputs
11 9 10 21 INVALID
Valid Signal Detector Output, Active Low. A logic-high indicates that
a valid RS-232 level is present on a receiver input.
12, 13 10, 11 11 12, 13, 14 T_IN TTL/CMOS Transmitter Inputs
14 12 12 23 FORCEON
Force-On Input, Active High. Drive high to override AutoShutdown
Plus, keeping transmitters and receivers on (FORCEOFF must be
high) (Table 1).
18 16 14 25 GND Ground
19 17 15 26 V
CC
+3.0V to +5.5V Single Supply Voltage
20 18 16 22 FORCEOFF
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 R2OUTB
TTL/CMOS Noninverting Complementary Receiver Outputs. Always
active.
— — — — EP
Exposed Pad (TQFN only). Solder the exposed pad to the ground, or
leave unconnected.
Maxim Integrated
7
MAX3224–MAX3227/MAX3244/MAX3245