MAX3320ACAP+T Maxim Integrated Products, MAX3320ACAP+T Datasheet - Page 7

• Manufacturer Part Number: MAX3320ACAP+T
• Description: IC TXRX RS232 250KBPS 20-SSOP
• Manufacturer: Maxim Integrated Products
• Type: Transceiverr

Specifications of MAX3320ACAP+T

• Number Of Drivers/receivers: 2/2
• Protocol: RS232
• Voltage - Supply: 3 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 20-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

reducing supply current to 4µA. This occurs if the RS-232
cable is disconnected or the connected peripheral trans-
mitters turn off. The system turns on again when a valid
transition occurs at any RS-232 receiver or transmitter
input. As a result, the system saves power without
changes to the existing BIOS or operating system. The
INVALID output is high when the receivers are active.
Since INVALID indicates the receiver inputs’ condition, it
can be used in any mode (Figure 2).
Tables 1 and 2 and Figure 2 summarize the MAX3320’s
operating modes. FORCEON and FORCEOFF override
the automatic circuitry and force the transceiver into its
normal operating state or into its low-power standby
state. When neither control is asserted, the IC enters
AutoShutdown Plus mode and selects between these
states automatically, based on the last receiver or
transmitter input edge received.
When shut down, the device’s charge pumps turn off,
V+ decays to V
mitter outputs turn off (high impedance). The time
required to exit shutdown is typically 25µs (Figure 3a).
If direct software control is desired, use INVALID to indi-
cate DTR or Ring Indicator signal. Connect FORCEOFF
and FORCEON together to bypass the AutoShutdown
Plus feature so the line acts like a SHDN input.
In addition to issuing a reset to the microprocessor (µP)
during power-up, power-down, and brownout condi-
tions, the MAX3320 is relatively immune to short-
duration, negative-going V
Typically, a V
reset threshold and lasts 20µs or less does not cause a
reset pulse (see Typical Operating Characteristics ).
Additional bypass capacitance mounted as close as
possible to the V
immunity.
Table 2. INVALID Truth Table
RS-232 SIGNAL PRESENT AT
3V to 5.5V, up to 250kbps True RS-232 Transceiver
with 4µA AutoShutdown Plus and Power-On Reset
RECEIVER INPUT
CC
CC
Yes
No
Software-Controlled Shutdown
transient that goes 100mV below the
CC
_______________________________________________________________________________________
, V- decays to ground, and the trans-
pin provides additional transient
CC
transitions (glitches).
Power-On Reset
OUTPUT
INVALID
H
L
Figure 2a. INVALID Functional Diagram, INVALID Low
Figure 2b. INVALID Functional Diagram, INVALID High
Figure 2c. AutoShutdown Plus Logic
Figure 2d. Power-Down Logic
+0.3V
-0.3V
INVALID ASSERTED IF BOTH RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR
AT LEAST 90 s.
R_IN
+2.7V
-2.7V
R_IN
INVALID DEASSERTED IF EITHER RECEIVER INPUT HAS BEEN BETWEEN +2.7V
AND -2.7V FOR LESS THAN 90 s.
* POWERDOWN IS ONLY AN INTERNAL SIGNAL.
THE TRANSMITTERS AND THE POWER SUPPLIES.
R_IN
IT CONTROLS THE OPERATIONAL STATUS OF
T_IN
AUTOSHDN
FORCEOFF
FORCEON
DETECT
DETECT
EDGE
EDGE
FORCEON
FORCEOFF
TIMER
30sec
S
R
TIMER
TIMER
90µs
90µs
R
R
POWERDOWN*
AUTOSHDN
INVALID
INVALID
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