19-1253; Rev 0; 8/97
3V to 5.5V, up to 250kbps True RS-232 Transceiver
with 4µA AutoShutdown Plus and Power-On Reset
_______________General Description
The MAX3320 combines a microprocessor (µP) super-
visory circuit with an RS-232 transceiver. The power-on
reset performs a single function: it asserts a reset signal
whenever the V
CC
supply voltage declines below a pre-
set threshold, staying asserted for at least 100ms after
V
CC
rises above the reset threshold. The MAX3320 has
an active-low
RESET
output, which is guaranteed to be in
the correct state for V
CC
down to 1V. The reset compara-
tor is designed to ignore fast transients on V
CC
. Reset
thresholds suitable for operation with a variety of supply
voltages are available.
The MAX3320 transceivers have a proprietary low-
dropout transmitter output stage, enabling true RS-232
performance with a dual charge pump powered from a
+3V to +5.5V supply. The device requires only four
small 0.1µF external charge-pump capacitors, and is
guaranteed to run at data rates of up to 250kbps. It
comes in the space-saving 20-pin SSOP package.
____________________________Features
o
Precise Monitoring of 5V and 3.3V Power-
Supply Voltages:
— 100ms (min) Power-On
RESET
Pulse Width
— Power-Supply Transient Immunity
— Guaranteed
RESET
Valid to V
CC
= 1V
o
4µA Supply Current Achieved with
AutoShutdown Plus
o
Receivers Always Active
o
Power-On Reset Always Active
o
4µA Low-Power Shutdown
o
250kbps Guaranteed Data Rate
MAX3320A/B/L/T
________________________Applications
Palmtop Computers
Portable/Battery-Powered Equipment
Hand-Held Equipment
Peripherals
Printers
______________Ordering Information
PART*
MAX3320_CAP
MAX3320_EAP
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
20 SSOP
20 SSOP
*
This part offers a choice of reset threshold voltage. From the
table below, select the suffix corresponding to the desired
threshold and insert it into the blank to complete the part
number.
__________________Pin Configuration
TOP VIEW
V+ 1
C2+ 2
C2- 3
V- 4
T1IN 5
T2IN 6
R1OUT 7
R2OUT 8
INVALID 9
RESET 10
20 C1+
19 V
CC
18 C1-
SUFFIX
A
B
L
T
RESET THRESHOLD
(V)
4.25
2.85
4.63
3.08
MAX3320
MAXxxx
17 GND
16 T1OUT
15 T2OUT
14 R1IN
13 R2IN
12 FORCEON
11 FORCEOFF
Typical Operating Circuit appears at end of data sheet.
SSOP
AutoShutdown Plus is a trademark of Maxim Integrated Products.
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
3V to 5.5V, up to 250kbps True RS-232 Transceiver
with 4µA AutoShutdown Plus and Power-On Reset
MAX3320A/B/L/T
ABSOLUTE MAXIMUM RATINGS
Short-Circuit Duration
V
CC
.............................................................................-0.3V to 6V
T_OUT....................................................................Continuous
V+ (Note 1) .................................................................-0.3V to 7V
Continuous Power Dissipation (T
A
= +70°C)
V- (Note 1)...................................................................0.3V to -7V
SSOP (derate 8.00mW/°C above +70°C) ....................640mW
V+ +
|
V-
|
(Note 1) ...................................................................13V
Input Voltages
Operating Temperature Ranges
T_IN,
FORCEOFF,
FORCEON ................................-0.3V to 6V
MAX3320_CAP ...................................................0°C to +70°C
R_IN.................................................................................±25V
MAX3320_EAP ................................................-40°C to +85°C
Output Voltages
Storage Temperature Range .............................-65°C to +160°C
T_OUT ..........................................................................±13.2V
Lead Temperature (soldering, 10sec) .............................+300°C
R_OUT,
INVALID, RESET.......................-0.3V
to (V
CC
+ 0.3V)
Note 1:
V+ and V- can have a magnitude of +7V (max), but their absolute difference cannot exceed +13V.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
CC
= 3V to 5.5V, C1–C4 = 0.1µF (tested at 3.3V ±10%), C1 = 0.047µF, C2–C4 = 0.33µF (tested at 5V ±10%), T
A
= T
MIN
to T
MAX
,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
DC CHARACTERISTICS
Power-Supply Current
Shutdown Supply Current
AutoShutdown Plus
Supply Current
CONDITIONS
No load, V
CC
= 3.3V or 5V, T
A
= +25°C
FORCEOFF
= GND, T
A
= +25°C
All R_IN unconnected, FORCEON = GND,
FORCEOFF
= V
CC
, all T_IN = V
CC
or GND, T
A
= +25°C
MIN
TYP
0.45
4.0
4.0
MAX
1.0
10
10
UNITS
mA
µA
µA
LOGIC INPUTS AND RECEIVER OUTPUTS
Input Logic Threshold Low
T_IN, FORCEON,
FORCEOFF
Input Logic Threshold High
Input Leakage Current
Input Hysteresis
Output Voltage Low
Output Voltage High
RECEIVER INPUTS
Input Voltage Range
Input Threshold Low
Input Threshold High
Input Hysteresis
Input Resistance
INVALID
OUTPUT
Receiver Input Threshold to
INVALID
Output High
Receiver Input Threshold to
INVALID
Output Low
INVALID
Output Voltage Low
2
Figure 3, positive threshold
Figure 3, negative threshold
Figure 3
I
OUT
= 1.6mA
-2.7
-0.3
T
A
= +25°C
3
V
CC
= 3.3V
V
CC
= 5V
V
CC
= 3.3V
V
CC
= 5V
T_IN, FORCEON,
FORCEOFF
T_IN, FORCEON,
FORCEOFF
T_IN, FORCEON,
FORCEOFF
I
OUT
= 1.6mA
I
OUT
= -1mA
V
CC
-
0.6
-25
0.6
0.8
1.2
1.5
1.5
1.8
0.3
5
V
CC
= 3.3V
V
CC
= 5V
2.0
2.4
±0.01
250
0.8
V
V
±1.0
0.4
µA
mV
V
V
V
CC -
0.1
25
V
V
2.4
2.4
7
2.7
V
V
kΩ
V
V
V
0.3
0.4
_______________________________________________________________________________________
3V to 5.5V, up to 250kbps True RS-232 Transceiver
with 4µA AutoShutdown Plus and Power-On Reset
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 3V to 5.5V, C1–C4 = 0.1µF (tested at 3.3V ±10%), C1 = 0.047µF, C2–C4 = 0.33µF (tested at 5V ±10%), T
A
= T
MIN
to T
MAX
,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
INVALID
Output Voltage High
Receiver Positive or Negative
Threshold to
INVALID
High
Receiver Positive or Negative
Threshold to
INVALID
Low
Receiver or Transmitter Edge
to Transmitters Enabled
Receiver or Transmitter Edge
to Shutdown
TRANSMITTER OUTPUTS
Output Voltage Swing
Output Resistance
Output Short-Circuit Current
Output Leakage Current
RESET
OUTPUT
RESET
Operating Voltage
Range
MAX3320_C
MAX3320_E
MAX3320A
RESET
Threshold
MAX3320B
MAX3320L
MAX3320T
I
SINK
= 1.2mA, V
CC
= reset threshold, MAX3320B/T
RESET
Output Voltage
I
SINK
= 3.2mA, V
CC
= reset threshold, MAX3320A/L
I
SINK
= 50µA, V
CC
> 1V, MAX3320_C
I
SINK
= 100µA, V
CC
> 1.2V, MAX3320_E
1.0
1.2
4.00
2.70
4.50
3.00
4.25
2.85
4.63
3.08
5.5
5.5
4.50
3.00
4.75
3.15
0.3
0.4
0.3
0.4
V
V
V
All transmitter outputs loaded with 3kΩ to ground
V
CC
= V+ = V- = GND, V
T_OUT
= ±2V
T_OUT = GND, T_IN = V
CC
or GND
V
T_OUT
= ±12V, V
CC
= 0 to 5.5V, transmitters disabled
±5.0
300
±5.4
10M
±35
±60
±25
V
Ω
mA
µA
I
OUT
= -1mA
Figure 3
Figure 3
CONDITIONS
MIN
V
CC
- 0.6
0.1
90
TYP
MAX
UNITS
V
µs
µs
MAX3320A/B/L/T
AUTOSHUTDOWN PLUS (FORCEON = GND,
FORCEOFF
= V
CC
)
Figure 5
Figure 3
15
25
30
60
µs
sec
_______________________________________________________________________________________
3
3V to 5.5V, up to 250kbps True RS-232 Transceiver
with 4µA AutoShutdown Plus and Power-On Reset
MAX3320A/B/L/T
TIMING CHARACTERISTICS
(V
CC
= 3V to 5.5V, C1–C4 = 0.1µF, C1–C4 = 0.1µF (for 3.3V ±10%), C1 = 0.047µF, C2–C4 = 0.33µF (tested at 5V ±10%),
T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Maximum Data Rate
Receiver Propagation Delay
Transmitter Skew
Receiver Skew
CONDITIONS
R
L
= 3kΩ, C
L
= 1000pF, one transmitter switching
R_IN to R_OUT, C
L
= 150pF
t
PHL
t
PLH
MIN
250
0.3
0.3
100
200
6
4
40
100
280
30
V/µs
30
µs
ms
TYP
MAX
UNITS
kbps
µs
ns
ns
|
t
PHL
- t
PLH
|
|
t
PHL
- t
PLH
|
C
L
= 150pF to
V
CC
= 3.3V, R
L
= 3kΩ to 7kΩ,
1000pf
measured from +3V to -3V or -3V to
C
L
= 150pF to
+3V, T
A
= +25°C
2500pf
100mV overdrive from reset threshold
V
CC
= reset threshold
Transition-Region Slew Rate
V
CC
to
RESET
Delay
RESET
Active Timeout Period
__________________________________________Typical Operating Characteristics
(V
CC
= 3.3V, 250kbps data rate, C1–C4 = 0.1µF, all transmitters loaded with 3kΩ. Typical values are at T
A
= +25°C, unless
otherwise noted.)
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
MAX3320 TOC01
SLEW RATE
vs. LOAD CAPACITANCE
MAX3320 TOC02
SUPPLY CURRENT
vs. LOAD CAPACITANCE WHEN
TRANSMITTING DATA
40
SUPPLY CURRENT (mA)
35
30
25
20
15
10
5
0
20kbps
120kbps
ONE TRANSMITTER AT
FULL DATA RATE INDICATED
ONE TRANSMITTER AT
1/16 DATA RATE INDICATED
250kbps
MAX3320 TOC03
7.5
V
T_OUT+
5.0
OUTPUT VOLTAGE (V)
2.5
0
-2.5
-5.0
V
T_OUT-
-7.5
0
1000
2000
3000
4000
ONE TRANSMITTER AT 250kbps
ONE TRANSMITTER AT 15.6kbps
LOAD = 3kΩ + C
L
12
10
SLEW RATE (V/us)
8
6
4
2
0
ONE TRANSMITTER AT 250kbps
ONE TRANSMITTER AT 15.6kbps
LOAD = 3kΩ + C
L
0
1000
2000
3000
4000
POSITIVE
SLEW
NEGATIVE
SLEW
45
5000
5000
0
1000
2000
3000
4000
5000
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
4
_______________________________________________________________________________________
3V to 5.5V, up to 250kbps True RS-232 Transceiver
with 4µA AutoShutdown Plus and Power-On Reset
____________________________Typical Operating Characteristics (continued)
(V
CC
= 3.3V, 250kbps data rate, C1–C4 = 0.1µF, all transmitters loaded with 3kΩ. Typical values are at T
A
= +25°C, unless
otherwise noted.)
MAXIMUM TRANSIENT DURATION
vs. RESET COMPARATOR OVERDRIVE
MAXIMUM TRANSIENT DURATION (µs)
MAX3320toc05
MAX3320A/B/L/T
NORMALIZED POWER-UP RESET
DELAY vs. TEMPERATURE
1.030
POWER-UP RESET DELAY
1.020
1.010
1.000
0.990
0.980
0.970
MAX3320 TOC06
300
250
SHUTDOWN MODE
200
150
100
50
0
10
NOT IN
SHUTDOWN
MODE
C
BYPASS
= 0.1µF
100
RESET COMPARATOR OVERDRIVE (mV)
1.040
0.960
1000
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
______________________________________________________________Pin Description
PIN
1
2
3
4
5, 6
7, 8
9
10
11
12
13, 14
15, 16
17
18
19
20
NAME
V+
C2+
C2-
V-
T_IN
R_OUT
INVALID
RESET
FORCEOFF
FORCEON
R_IN
T_OUT
GND
C1-
V
CC
C1+
5.5V generated by the charge pump
Positive terminal of inverting charge-pump capacitor
Negative terminal of inverting charge-pump capacitor
-5.5V generated by the charge pump
TTL/CMOS Transmitter Inputs (T1IN and T2IN)
TTL/CMOS Receiver Outputs (R1OUT and R2OUT)
Output of the Valid Signal Detector. Asserts when no valid RS-232 levels are present on any of
the receiver inputs for 90µs.
RESET
Output.
RESET
remains low while V
CC
is below the reset threshold, and for 280ms (max)
after V
CC
rises above the reset threshold.
Force-Off Input. Drive
FORCEOFF
low to shut down transmitters and on-board power supply.
This overrides AutoShutdown Plus and FORCEON (Table 1).
Force-On Input. Drive FORCEON high to override AutoShutdown Plus, keeping transmitters on
(FORCEOFF must be high) (Table 1).
RS-232 Receiver Inputs (R2IN and R1IN)
RS-232 Transmitter Outputs (T2OUT and T1OUT)
Ground
Negative terminal of voltage-doubler charge-pump capacitor
+3V to +5.5V Supply Voltage
Positive terminal of voltage-doubler charge-pump capacitor
5
FUNCTION
_______________________________________________________________________________________
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