MAX3229EEBV MAXIM [Maxim Integrated Products], MAX3229EEBV Datasheet - Page 6

• Manufacturer Part Number: MAX3229EEBV
• Manufacturer: MAXIM [Maxim Integrated Products]

±15kV ESD-Protected +2.5V to +5.5V
RS-232 Transceivers in UCSP
Table 1. Operating Supply Options
The MAX3228E/MAX3229E internal power supply con-
sists of a dual-mode regulated charge pump. For sup-
ply voltages above +3.7V, the charge pump will
generate +5.5V at V+ and -5.5V at V-. The charge
pumps operate in a discontinuous mode. If the output
voltages are less than ±5.5V, the charge pumps are
enabled, if the output voltages exceed ±5.5V, the
charge pumps are disabled.
For supply voltages below +2.85V, the charge pump
will generate +4.0V at V+ and -4.0V at V-. The charge
pumps operate in a discontinuous mode. If the output
voltages are less than ±4.0V, the charge pumps are
enabled, if the output voltages exceed ±4.0V, the
charge pumps are disabled.
Each charge pump requires a flying capacitor (C1, C2)
and a reservoir capacitor (C3, C4) to generate the V+
and V- supply voltages.
6
MAX3228E
C6, D6
E3, E4
E5, E6
_______________________________________________________________________________________
C5
D1
E1
E2
Regulated Voltage Only
Regulated Voltage Only
SYSTEM SUPPLY (V)
3 NiCad/NiMh Cells
Dual-Mode Regulated Charge-Pump
(V
(V
PIN
1 Li+ Cell
CC
CC
MAX3229E
falling)
falling)
C5
C6
D1
E1
E2
E3
E5
Voltage Generation in the
Detailed Description
FORCEOFF
INVALID
R_OUT
T_OUT
NAME
GND
R_IN
C1-
Switchover Region
Voltage Converter
+2.4 to +4.2
+2.4 to +3.8
+3.0 to +5.5
+2.5 to +3.0
V
CC
FORCEOFF Input, Active-Low. Drive FORCEOFF low to shut down transmitters,
receivers, and on-board charge pump. This overrides all automatic circuitry and
FORCEON. Pulls itself high internally if not connected.
Receiver Output(s)
Negative Terminal of Positive Regulated Charge-Pump Capacitor
Ground
Output of Valid Signal Detector. INVALID is enabled low if no valid RS-232 level is
present on any receiver input.
RS-232 Transmitter Output(s)
RS-232 Receiver Input(s)
(V)
Regulated System Voltage
Regulated System Voltage
The MAX3228E/MAX3229E include a switchover circuit
between these two modes that have approximately
400mV of hysteresis around the switchover point. The
hysteresis is shown in Figure 1. This large hysteresis
eliminates mode changes due to power-supply
bounce.
For example, a three-cell NiMh battery system starts at
V
output voltage of ±5.5V. As the battery discharges, the
Figure 1. V+ Switchover for Changing V
CC
+3.0 to +5.5
+2.5 to +3.0
V
= +3.6V, and the charge pump will generate an
L
(V)
V
CC
V+
FUNCTION
Pin Description (continued)
20ms/div
Compliant/Compatible
Compliant/Compatible
RS-232 MODE
CC
Compatible
Compliant
4V
0
6V
0