Maxim MAX3380E 2.35v to 5.5v, 1î¼a, 2tx/2rx rs-232 transceivers with â±15kv esd-protected i/o and logic pin Datasheet

19-2128; Rev 0; 8/01
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
Features
♦ ±15kV ESD Protection on All CMOS and RS-232
Inputs and Outputs (Except INVALID)
±15kV Human Body Model
±15kV IEC 1000-4-2 Air-Gap Discharge
±8kV IEC 1000-4-2 Contact Discharge
♦ Operates Over Entire Li+ Battery Range
♦ Low Logic Threshold Down to +1.65V for
Compatibility with Cell Phone Logic Supply Voltages
♦ 1µA Low-Power AutoShutdown Plus Mode
♦ Compatible with Next-Generation GSM Data Rates
♦ 20-Pin TSSOP Package
Ordering Information
PART
20 TSSOP
20 TSSOP
20 TSSOP
MAX3381EEUP
-40°C to +85°C
20 TSSOP
Typical Operating Circuit
C1
0.1µF
C2
0.1µF
TTL/CMOS
INPUTS
VCC
VL
C1+
FORCEON
C5
0.1µF
FORCEOFF
+3.3V
V+
C3
0.1µF
C1C2+
MAX3380E/
MAX3381E
V-
C2T1IN
T1OUT
T2IN
T2OUT
C4
0.1µF
RS-232
OUTPUTS
VL
GPS Receivers
Digital Cameras
R1OUT
TTL/CMOS
OUTPUTS
AutoShutdown Plus is a trademark of Maxim Integrated Products
PIN-PACKAGE
0°C to +70°C
-40°C to +85°C
0°C to +70°C
Applications
Cell Phone Data Lump Cables
PDA Data Lump Cables
TEMP. RANGE
MAX3380ECUP
MAX3380EEUP
MAX3381ECUP
R1IN
5kΩ
VL
R2OUT
RS-232
INPUTS
R2IN
5kΩ
Pin Configuration appears at end of data sheet.
GND
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX3380E/MAX3381E
General Description
The MAX3380E/MAX3381E are +2.35V to +5.5V-powered EIA/TIA-232 and V.28/V.24 communication interfaces with low power requirements, high data-rate
capabilities, and enhanced electrostatic discharge
(ESD) protection on both the TTL and RS-232 sides.
The MAX3380E/MAX3381E have two receivers and two
transmitters. All RS-232 inputs, outputs, and logic input
pins are protected to ±15kV using IEC 1000-4-2 AirGap Discharge method and the Human Body Model,
and ±8kV using IEC 1000-4-2 Contact Discharge
method.
The proprietary low-dropout transmitter output stage
enables true RS-232 performance from a +3.1V to
+5.5V supply with a dual charge pump. The parts
reduce the transmitter output levels to RS-232-compatible levels with no increase in supply current for supplies less than +3.1V and greater than +2.35V. The
+2.35V to +5.5V operating range is fully compatible
with lithium-ion (Li+) batteries. The charge pump
requires only four small 0.1µF capacitors for operation.
The MAX3380E/MAX3381E transceivers use Maxim’s
revolutionary AutoShutdown Plus™ feature to automatically enter a 1µA shutdown mode. These
devices shut down the on-board power supply and
drivers when they do not sense a valid signal transition for 30 seconds on either the receiver or transmitter inputs.
The MAX3380E is capable of transmitting data at
rates of 460kbps while maintaining RS-232 output
levels, and the MAX3381E operates at data rates up
to 250kbps. The MAX3381E offers a slower slew rate
for applications where noise and EMI are issues. The
MAX3380E/MAX3381E have a unique V L pin that
allows interoperation in mixed-logic voltage systems
down to +1.65V. Both input and output logic levels
are referenced to the VL pin. The MAX3380E/MAX3381E
are available in a space-saving TSSOP package.
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
ABSOLUTE MAXIMUM RATINGS
Short-Circuit Duration T_OUT to GND........................Continuous
Continuous Power Dissipation (TA = +70°C)
20-Pin TSSOP (derate 10.9mW/°C over +70°C) .........879mW
Operating Temperature Ranges
MAX3380ECUP/MAX3381ECUP........................0°C to +70°C
MAX3380EEUP/MAX3381EEUP .....................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
VCC to GND ...........................................................-0.3V to +6.0V
VL to GND..............................................................-0.3V to +6.0V
V+ to GND .............................................................-0.3V to +7.0V
V- to GND ..............................................................+0.3V to -7.0V
V+ + |V-| (Note 1) .................................................................+13V
Input Voltages
T_IN, FORCEON, FORCEOFF to GND ...............-0.3V to +6.0V
R_IN to GND .....................................................................±25V
Output Voltages
T_OUT to GND...............................................................±13.2V
R_OUT, INVALID to GND...........................-0.3V to (VL + 0.3V)
Note 1: V+ and V- can have maximum magnitudes of +7V, 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
(VCC = +2.35V to +5.5V, VL = +1.65V to +5.5V. When VCC < +4.5V, C1 = C2 = C3 = C4 = 0.1µF; when VCC ≥ +4.5V, C1 = 0.047µF,
C2 = C3 = C4 = 0.33µF; TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL = +3.3V, TA = +25°C.)
PARAMETER
Supply Current, AutoShutdown
Plus
Supply Current, Normal Operation
SYMBOL
ICC
CONDITIONS
MIN
MAX
10
FORCEOFF = GND
ICC
TYP
Receivers idle, VT_IN = VCC or GND,
FORCEON = GND, FORCEOFF = VCC
FORCEON = FORCEOFF = VL, no load
1
10
0.3
1
UNITS
µA
mA
LOGIC INPUTS (T_IN, FORCEON, FORCEOFF)
Input Logic Threshold Low
VIL
Input Logic Threshold High
VIH
VCC = +5.5V, VL = +5.5V
0.4
VCC = +2.5V, VL = +1.65V
0.4
1.2
V
VCC = +5.5V, VL = +5.5V
VL ✕ 0.66
VCC = +2.5V, VL = +1.65V
VL ✕ 0.66
Transmitter Input Hysteresis
0.5
±0.01
Input Leakage Current
V
V
±1
µA
0.5
V
RECEIVER OUTPUTS (R_OUT) AND INVALID
Output Voltage Low
IOUT = 500µA
Output Voltage High
IOUT = -500µA
VL - 0.4 VL - 0.2
V
RECEIVER INPUTS (R_IN)
Input Voltage Range
-25
Input Threshold Low
TA = +25°C
Input Threshold High
TA = +25°C
VL = +3.3V
0.6
1.2
VL = +5.0V
0.8
1.5
1.5
2.4
VL = +5.0V
1.8
2.4
2
0.3
TA = +25°C
3
5
_______________________________________________________________________________________
V
V
VL = +3.3V
Input Hysteresis
Input Resistance
+25
V
V
7
kΩ
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
(VCC = +2.35V to +5.5V, VL = +1.65V to +5.5V. When VCC < +4.5V, C1 = C2 = C3 = C4 = 0.1µF; when VCC ≥ +4.5V, C1 = 0.047µF,
C2 = C3 = C4 = 0.33µF; TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL = +3.3V, TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
AutoShutdown Plus (FORCEON = GND, FORCEOFF = VL)
Receiver Input Threshold to
INVALID Output High
Figure 3
Receiver Input Threshold to
INVALID Output Low
Figure 3
Positive threshold
Negative threshold
2.7
-2.7
-0.3
0.3
V
V
Receiver Positive or Negative
Threshold to INVALID High
tINVL
VCC = +5.0V, Figure 4
0.3
µs
Receiver Positive or Negative
Threshold to INVALID Low
tINVH
VCC = +5.0V, Figure 4
30
µs
Receiver or Transmitter Edge to
Transmitters Enabled
tWU
VCC = +5.0V, Figure 4
15
µs
tAUTOSHDN VCC = +5.0V, Figure 4
30
s
Receiver or Transmitter Edge to
Transmitters Shutdown
TRANSMITTER OUTPUTS
VCC Mode Switch Point
(VCC Falling)
T_OUT = ±5.0V to ±3.7V
2.95
3.1
3.25
V
VCC Mode Switch Point
(VCC Rising)
T_OUT = ±3.7V to ±5.5V
3.3
3.5
3.7
V
VCC Mode Switch Point
Hysteresis
Output Voltage Swing
400
All transmitter
outputs loaded
with 3kΩ to ground
VCC = +3.25V to +5.5V,
VCC falling
±5
VCC = +2.5V to +2.95V,
VCC falling
±3.7
VCC = 0, transmitter output = ±2.0V
Output Resistance
±5.4
V
300
Ω
10M
Output Short-Circuit Current
Output Leakage Current
mV
VOUT = ±12V, transmitters disabled
±60
mA
±25
µA
ESD PROTECTION
R_IN, T_OUT, R_OUT, T_IN,
FORCEON, FORCEOFF
Human Body Model
±15
IEC 1000-4-2 Air-Gap Discharge Method
±15
IEC 1000-4-2 Contact Discharge Method
±8
kV
_______________________________________________________________________________________
3
MAX3380E/MAX3381E
ELECTRICAL CHARACTERISTICS (continued)
TIMING CHARACTERISTICS
(VCC = +2.35V to +5.5V, VL = +1.65V to +5.5V. When VCC < +4.5V, C1 = C2 = C3 = C4 = 0.1µF; when VCC ≥ +4.5V, C1 = 0.047µF,
C2 = C3 = C4 = 0.33µF; TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL = +3.3V, TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
RL = 3kΩ, CL = 1000pF, one
transmitter switching
Maximum Data Rate
tPLH
Receiver Propagation Delay
MAX3381E
250
MAX3380E
460
MAX
UNITS
kbps
0.15
Receiver input to receiver output, CL = 100pF
tPHL
TYP
µs
0.15
Transmitter Skew
tPHL- tPLH (Note 2)
200
ns
Receiver Skew
tPHL- tPLH
50
ns
Transition Region Slew Rate
(MAX3380E)
VCC = +4.2V, -3.0V < T_OUT< +3.0V,
RL = 3kΩ, CL = 250pF to 1000pF, TA = +25°C
20
100
V/µs
Transition Region Slew Rate
(MAX3381E)
VCC = +4.2V, -3.0V < T_OUT< +3.0V,
RL = 3kΩ, CL = 150pF to 1000pF, TA = +25°C
6
30
V/µs
Transition Region Slew Rate
(MAX3380E)
VCC = +2.35V, -3.0V < T_OUT< +3.0V,
RL = 3kΩ, CL = 250pF to 1000pF, TA = +25°C
30
V/µs
Transition Region Slew Rate
(MAX3381E)
VCC = +2.35V, -3.0V < T_OUT< +3.0V,
RL = 3kΩ, CL = 250pF to 1000pF, TA = +25°C
10
V/µs
Note 2: Transmitter skew is measured at the transmitter zero crosspoint.
Typical Operating Characteristics
(VCC = VL = +4.2V, C1 = 0.22µF, C2 = C3 = C4 = 1µF, C5 = 0.1µF parallel with 47µF, RL = 3kΩ, CL = 1000pF, data rate is 250kbps,
TA = +25°C, unless otherwise noted.)
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
4
2
0
-2
-4
VOUT-6
500
1000
1500
2000
LOAD CAPACITANCE (pF)
2500
3000
35
30
4
2
0
-2
25
VCC = +4.2V
20
15
10
VOUT-
-4
MAX3380E toc03
VOUT+
VCC = +2.5V
5
-6
0
4
6
40
SLEW RATE (V/µs)
VOUT+
VCC = +2.5V
MAX3380E
SLEW RATE vs. LOAD CAPACITANCE
MAX3380E toc02
6
8
TRANSMITTER OUTPUT VOLTAGE (V)
VCC = +4.2V
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
MAX3380E toc01
8
TRANSMITTER OUTPUT VOLTAGE (V)
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
0
0
500
1000
1500
2000
LOAD CAPACITANCE (pF)
2500
3000
0
500
1000
1500
2000
LOAD CAPACITANCE (pF)
_______________________________________________________________________________________
2500
3000
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
SUPPLY CURRENT (mA)
VCC = +4.2V
11
10
VCC = +2.5V
60
50
30
8
20
7
10
6
250kbps
40
20kbps
500
1000
1500
2000
2500
3000
0
500
LOAD CAPACITANCE (pF)
1000
1500
2000
2500
2
0
-2
VOUT-
-4
3000
2.5
3.5
4.5
SUPPLY VOLTAGE (V)
25
1 TRANSMITTER SWITCHING
20
SUPPLY CURRENT (mA)
VOUT+
5.5
SUPPLY CURRENT
vs. SUPPLY VOLTAGE (VCC FALLING)
MAX3380E toc07
TRANSMITTER OUTPUT VOLTAGE (V)
8
4
2
0
-2
15
10
5
VOUT-
-4
VOUT+
4
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE (VCC RISING)
6
6
-6
0
0
8
MAX3380E toc08
9
460kbps
TRANSMITTER OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE (VCC FALLING)
TRANSMITTER OUTPUT VOLTAGE (V)
12
1 TRANSMITTER SWITCHING
70
MAX3381E toc05
13
SLEW RATE (V/µs)
80
MAX3380E toc04
14
SUPPLY CURRENT vs. LOAD CAPACITANCE
WHEN TRANSMITTING DATA
MAX3380E toc06
MAX3381E
SLEW RATE vs. LOAD CAPACITANCE
0
-6
2.5
3.5
4.5
SUPPLY VOLTAGE (V)
2.5
5.5
3.5
4.5
MAX3380E
DATASTREAM VCC = +4.2V
MAX3380E
DATASTREAM VCC = +2.5V
MAX3380E toc09
MAX3380E toc10
5V
5V
T_IN
5V/div
0
T_IN
5V/div
0
5V
T_OUT
5V/div
5.5
SUPPLY VOLTAGE (V)
0
5V
T_OUT
5V/div
0
-5V
-5V
VCC = VL = +2.5V
1µs/div
1µs/div
_______________________________________________________________________________________
5
MAX3380E/MAX3381E
Typical Operating Characteristics (continued)
(VCC = VL = +4.2V, C1 = 0.22µF, C2 = C3 = C4 = 1µF, C5 = 0.1µF parallel with 47µF, RL = 3kΩ, CL = 1000pF, data rate is 250kbps,
TA = +25°C, unless otherwise noted.)
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
MAX3380E/MAX3381E
Pin Description
PIN
NAME
1
C1+
Positive Terminal of Voltage-Doubler Charge-Pump Capacitor
—
2
V+
+5.5V/+4.0V Generated by the Charge Pump
—
3
C1-
Negative Terminal of Voltage-Doubler Charge-Pump Capacitor
—
4
C2+
Positive Terminal of Inverting Charge-Pump Capacitor
—
5
C2-
Negative Terminal of Inverting Charge-Pump Capacitor
—
6
V-
7
INVALID
8, 9
T_IN
10, 11
R_OUT
12
FORCEON
13
VL
14, 15
R_IN
16, 17
T_OUT
18
GND
19
FORCEOFF
20
VCC
-5.5V/-4.0V Generated by the Charge Pump
—
INVALID is asserted if any inputs of the receivers are in an invalid state;
-0.3V < VR_IN < +0.3V
—
TTL/CMOS Transmitter Inputs Referenced to VL (T1IN, T2IN)
✔
TTL/CMOS Receiver Outputs Referenced to VL (R2OUT, R1OUT)
✔
Force-On Input. Drive high to override automatic circuitry keeping transmitters on
(FORCEOFF must be high) (Table 1).
✔
Logic Level Supply. +1.65V to +5.5V, sets CMOS logic thresholds and CMOS
outputs.
—
RS-232 Receiver Inputs (R2IN, R1IN)
✔
RS-232 Transmitter Outputs (T2OUT, T1OUT)
✔
Ground
—
Force-Off Input. Drive low to shut down transmitters and on-board power supply.
This overrides all automatic circuitry and FORCEON (Table 1).
✔
+2.35V to +5.5V Supply Voltage
—
Detailed Description
The MAX3380E/MAX3381E are RS-232 transceivers that
maximize battery life by reducing current consumption
at low battery levels. When the supply voltage is above
+3.7V, the RS-232 outputs are at ±5.5V, which is compliant with the RS-232 standard. As the supply voltage
drops below the +3.1V set point, the RS-232 outputs
change to ±3.7V, which is compatible with the RS-232
standard. The outputs will remain at the compatible levels until the supply voltage rises above +3.5V, where
they return to compliant levels. 400mV of hysteresis protects against power-supply bounce that may cause
numerous mode changes.
Most devices that use charge pumps to double and
invert voltages consume higher current when the supply
voltage is less than half of the required output voltage.
This is due to the fact that the charge pump is constantly operating because the output voltage is below the
regulation voltage. This requires more supply current
because the output will never reach the regulation voltage and switch off. The MAX3380E/MAX3381E reduce
6
ESD
PROTECTED
FUNCTION
the output voltage requirement allowing the charge
pump to operate with supply voltages down to +2.35V.
Dual-Mode Regulated Charge-Pump
Voltage Converter
The MAX3380E/MAX3381Es’ internal power supply is a
dual-mode regulated charge pump. The output regulation point depends on VCC and the direction in which
VCC moves through the switchover region of +2.95V <
VCC < +3.7V.
For supply 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 +2.95V, the charge pump
will generate +4.0V at V+ and -4.0V at V-. The charge
pumps operate in a discontinuous mode.
Each charge pump requires a flying capacitor (C1, C2)
and a reservoir capacitor (C3, C4) to generate the V+
and V- supplies (see Typical Operating Circuit).
_______________________________________________________________________________________
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
The MAX3380E/MAX3381E include a switchover circuit
between RS-232-compliant and RS-232-compatible
modes that has approximately 400mV of hysteresis
around the switchover point. The hysteresis is shown in
Figure 1. This large hysteresis helps to avoid mode
change under battery or power-supply bounce.
Under a decaying VCC, the charge pump will generate
an output voltage of ±5.5V with a V CC input range
between +3.1V and +5.5V. When VCC drops below the
switchover point of +3.1V, the charge pump switches
into RS-232-compatible mode generating ±4V.
When VCC is rising, the charge pump will generate an
output voltage of ±4.0V, while VCC is between +2.5V
and +3.5V. When VCC rises above the switchover voltage of +3.5V, the charge pump switches to RS-232compliant mode to generate an output voltage of ±5.5V.
RS-232 Transmitters
The transmitters are inverting level translators that convert CMOS-logic levels to RS-232-compatible levels.
The MAX3380E/MAX3381E will automatically reduce
the RS-232-compliant levels from ±5.5V to ±3.7V when
VCC falls below approximately +3.1V. The reduced levels are RS-232-compatible and reduce supply current
requirements that help preserve the battery. Built-in
hysteresis of approximately 400mV for VCC ensures
that the RS-232 output levels do not change if VCC is
noisy or has a sudden current draw causing the supply
voltage to drop slightly. The outputs will return to RS232-compliant levels (±5.5V) when VCC rises above
approximately +3.5V.
+4.5V
VCC
2V/div
+2.5V
+5.8V
V+
2V/div
+4.4V
20ms/div
Figure 1. V+ Switchover for Changing Vcc
The MAX3380E/MAX3381E transmitters guarantee a data
rate of 460kbps/250kbps, respectively, with worst-case
loads of 3kΩ in parallel with 1000pF. Transmitters can be
paralleled to drive multiple receivers.
When FORCEOFF is driven to ground, the transmitters
are disabled and the outputs go into high impedance;
receivers remain active. When the AutoShutdown Plus
circuitry senses that all receiver and transmitter inputs
are inactive for more than 30s, the transmitters are disabled and the outputs go into a high-impedance state,
and the receivers remain active. When the power is off,
the MAX3380E/MAX3381E permit the outputs to be driven up to ±12V.
The transmitter inputs have a 400kΩ active positive
feedback resistor. They will retain a valid logic level if
the driving signal is removed or goes high impedance.
Connect unused transmitter inputs to VCC or ground.
RS-232 Receivers
The receivers convert RS-232 signals to logic levels
referred to VL. Both receivers are active in shutdown
(Table 1).
AutoShutdown Plus Mode
The MAX3380E/MAX3381E achieve a 1µA supply current
with Maxim’s AutoShutdown Plus feature, which operates
when FORCEOFF is high and FORCEON is low. When
these devices do not sense a valid signal transition on
any receiver and transmitter input for 30s, the on-board
charge pumps are shut down, reducing supply current
to 1µA. This occurs if the RS-232 cable is disconnected
or if the connected peripheral transmitters are turned off,
and if the UART driving the transmitter inputs is inactive.
The system turns on again when a valid transition is
applied to any RS-232 receiver or transmitter input. As a
result, the system saves power without changes to the
existing BIOS or operating system.
Figures 2a and 2b show valid and invalid RS-232
receiver voltage levels. INVALID indicates the receiver
input’s condition, and is independent of the FORCEON
and FORCEOFF states. Figure 2 and Table 1 summarize the MAX3380E/MAX3381E’s operating modes.
FORCEON and FORCEOFF override AutoShutdown
Plus circuitry. When neither control is asserted, the IC
selects between these states automatically based on
the last receiver or transmitter input edge received.
By connecting FORCEON to INVALID, the MAX3380E/
MAX3381E is shut down when no valid receiver level and
no receiver or transmitter edge is detected for 30s, and
wakes up when a receiver or transmitter edge is detected (Figure 2c).
_______________________________________________________________________________________
7
MAX3380E/MAX3381E
Voltage Generation in the
Switchover Region
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
Table 1. AutoShutdown Plus Truth Table
FORCEON
FORCEOFF
VALID
RECEIVER
LEVEL
RECEIVER OR
TRANSMITTER EDGE
WITHIN 30s
T_OUT
R_OUT
Shutdown
(Forced Off)
X
0
X
X
High-Z
Active
Normal Operation
(Forced On)
1
1
X
X
Active
Active
Normal Operation
(AutoShutdown
Plus)
0
1
X
Yes
Active
Active
Shutdown
(AutoShutdown
Plus)
0
1
X
No
High-Z
Active
Normal Operation
INVALID
1
Yes
X
Active
Active
Normal Operation
INVALID
1
X
Yes
Active
Active
Shutdown
INVALID
1
No
No
High-Z
Active
Normal Operation
(AutoShutdown)
INVALID
INVALID
Yes
X
Active
Active
Shutdown
(AutoShutdown)
INVALID
INVALID
No
X
High-Z
Active
OPERATION
STATUS
X = Don’t care
+2.7V
+0.3V
R_IN
-0.3V
R_IN
30µs
TIMER
R
INVALID
INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR
AT LEAST 30µs.
Figure 2a. INVALID Functional Diagram, INVALID Low
8
-2.7V
0.3µs
TIMER
R
INVALID
INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN BETWEEN +2.7V AND -2.7V
FOR LESS THAN 30µs.
Figure 2b. INVALID Functional Diagram, INVALID High
_______________________________________________________________________________________
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
S
30s
TIMER
EDGE
DETECT
R_IN
FORCEOFF
FORCEOFF
POWERDOWN*
FORCEON
AUTOSHDN
AUTOSHDN
R
* POWERDOWN IS ONLY AN INTERNAL SIGNAL.
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.
FORCEON
Figure 2c. AutoShutdown Plus Logic
Figure 2d. Power-Down Logic
TRANSMITTERS ENABLED, INVALID HIGH
By connecting FORCEON and FORCEOFF to INVALID,
the MAX3380E/MAX3381E are shut down when no valid
receiver level is detected.
+2.7V
INDETERMINATE
+0.3V
AutoShutdown, TRANSMITTERS DISABLED,
1µA SUPPLY CURRENT INVALID LOW
0
-0.3V
INDETERMINATE
-2.7V
TRANSMITTERS ENABLED, INVALID HIGH
VL Logic Supply Input
Unlike other RS-232 interface devices where the receiver outputs swing between 0 and VCC, the MAX3380E/
MAX3381E feature a separate logic supply input (VL)
that sets VOH for the receiver and INVALID outputs. VL
also sets the threshold for the transmitter inputs,
FORCEON and FORCEOFF. This feature allows a great
deal of flexibility in interfacing to many different types of
systems with different logic levels. Connect this input to
Figure 3. AutoShutdown Trip Levels
RECEIVER
INPUTS
INVALID
} REGION
TRANSMITTER
INPUTS
TRANSMITTER
OUTPUTS
INVALID
OUTPUT
VL
0
tINVL
tINVH
tAUTOSHDN
tAUTOSHDN
tWU
tWU
V+
VCC
0
V-
Figure 4. AutoShutdown Plus/INVALID Timing Diagram
_______________________________________________________________________________________
9
MAX3380E/MAX3381E
EDGE
DETECT
T_IN
RC
1MΩ
CHARGE-CURRENT
LIMIT RESISTOR
HIGHVOLTAGE
DC
SOURCE
Cs
100pF
RD
1500Ω
RC
50MΩ to 100MΩ
DISCHARGE
RESISTANCE
CHARGE-CURRENT
LIMIT RESISTOR
DEVICE
UNDER
TEST
STORAGE
CAPACITOR
Figure 5a. Human Body ESD Test Model
IP 100%
90%
Ir
HIGHVOLTAGE
DC
SOURCE
Cs
150pF
RD
330Ω
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
DEVICE
UNDER
TEST
Figure 6a. IEC 1000-4-2 ESD Test Model
I
100%
90%
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
IPEAK
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
AMPERES
36.8%
10%
10%
0
0
tRL
TIME
tDL
CURRENT WAVEFORM
Figure 5b. Human Body Current Waveform
the host logic supply (+1.65V to +5.5V). The VL input
will draw a maximum current of 20µA with receiver outputs unloaded.
±15kV ESD Protection
Maxim has developed state-of-the-art structures to protect these pins against an ESD of ±15kV without damage. The ESD structures withstand high ESD in all states:
normal operation, shutdown, and power-down. After an
ESD event, Maxim’s “E” version devices keep working
without latch-up, whereas competing RS-232 products
can latch and must be powered down to remove latchup. ESD protection can be tested in various ways. The
transmitter and receiver outputs and receiver and logic
inputs of this product family are characterized for protection to the following limits:
• ±15kV using the Human Body Model
• ±8kV using the Contact Discharge method specified in IEC 1000-4-2
• ±15kV using IEC 1000-4-2’s Air-Gap Discharge
method
10
tr = 0.7ns to 1ns
30ns
t
60ns
Figure 6b. IEC 1000-4-2 ESD Generator Current Waveform
ESD Test Conditions
ESD performance depends on a variety of conditions.
Contact Maxim for a reliability report that documents
test setup, methodology, and results.
Human Body Model
Figure 5a shows the Human Body Model, and Figure
5b shows the current waveform it generates when discharged into a low impedance. This model consists of
a 100pF capacitor charged to the ESD voltage of interest, which is then discharged into the test device
through a 1.5kΩ resistor.
IEC 1000-4-2
The IEC 1000-4-2 standard covers ESD testing and
performance of finished equipment; it does not specifically refer to ICs. The MAX3380E/MAX3381E help you
design equipment that meets Level 4, the highest level
of IEC 1000-4-2 without the need for additional ESDprotection components. The major difference between
tests done using the Human Body Model and IEC
1000-4-2 is higher peak current in IEC 1000-4-2,
because series resistance is lower in the IEC 1000-4-2
model. Hence, the ESD withstand voltages measured
______________________________________________________________________________________
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
Machine Model
The Machine Model for ESD tests all pins using a
200pF storage capacitor and zero discharge resistance. Its objective is to emulate the stress caused by
contact that occurs with handling and assembly during
manufacturing. All pins require this protection during
manufacturing, not just RS-232 inputs and outputs.
Therefore, after PC board assembly, the Machine
Model is less relevant to I/O ports.
Applications Information
Capacitor Selection
The capacitor type used for C1–C4 is not critical for
proper operation. Polarized or nonpolarized capacitors
can be used. The charge pump requires 0.1µF capacitors for +3.3V operation. For other supply voltages, see
Table 2 for required capacitor values. Do not use values smaller than those listed in Table 2. Increasing the
capacitor values (e.g., by a factor of 2) reduces ripple
on the transmitter outputs and slightly reduces power
consumption. C2, C3, and C4 can be increased without
changing C1’s value. However, do not increase C1
without also increasing the values of C2, C3, C4, and
C5 to maintain the proper ratios (C1 to the other capacitors).
When using the minimum required capacitor values,
make sure the capacitor value does not degrade
excessively with temperature. If in doubt, use capacitors with a large nominal value. The capacitor’s equivalent series resistance (ESR) usually rises at low
temperatures and influences the amount of ripple on
V+ and V-.
Power-Supply Decoupling
In most circumstances, connect a 0.1µF capacitor from
VCC to GND. This capacitor is for noise reduction. If the
MAX3380E/MAX3381E are used in a data cable application, add a 47µF capacitor from VCC to ground. The
47µF capacitor is used to ensure that the current needed during power-up is supplied to the device. In applications that are sensitive to power-supply noise,
decouple VCC to ground with a capacitor of the same
value as charge-pump capacitor C1. Connect bypass
capacitors as close to the IC as possible.
Transmitter Outputs when Recovering
from Shutdown
Figure 7 shows two transmitter outputs when exiting
shutdown mode. As they become active, the two transmitter outputs are shown going to opposite RS-232 levels (one transmitter input is high, the other is low). Each
transmitter is loaded with 3kΩ in parallel with 1000pF.
The transmitter outputs display no ringing or undesirable transients as they come out of shutdown. Note that
the transmitters are enabled only when the magnitude
of V- exceeds approximately 3V.
High Data Rates
The MAX3380E/MAX3381E maintain the RS-232 ±5.0V
minimum transmitter output voltage even at high data
rates. Figure 8 shows a transmitter loopback test circuit. Figure 9 shows a loopback test result for the
MAX3380E at 460kbps with true RS-232 output voltage
levels (VCC = +4.2V). Figure 10 shows the same test
with RS-232-compatible levels (V CC = +2.5V). With
data rates as high as 460kbps, the MAX3380E is compatible with 2.5-Generation GSM standards.
5V/div
5V FORCEON =
0 FORCEOFF
6V T2OUT
2V/div
0
Table 2. Minimum Required Capacitor
Values
VCC (V)
C1, C5 (µF)
C2, C3, C4 (µF)
+2.35 to +3.6
0.1
0.1
+4.5 to +5.5
0.047
0.33
+2.35 to +5.5
0.22
1
T1OUT
6V
4µs/div
VCC = 3.3V, C1–C4 = 0.1µF, CLOAD = 1000pF
Figure 7. Transmitter Outputs when Recovering from Shutdown
or Powering Up
______________________________________________________________________________________
11
MAX3380E/MAX3381E
to IEC 1000-4-2 are generally lower than that measured
using the Human Body Model. Figure 6a shows the IEC
1000-4-2 model, and Figure 6b shows the current
waveform for the ±8kV IEC 1000-4-2 Level 4 ESD
Contact Discharge test.
The Air-Gap test involves approaching the device with
a charged probe. The Contact Discharge method connects the probe to the device before the probe is energized.
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
For Figure 9 and Figure 10, a single transmitter was driven at 460kbps, and all transmitters were loaded with
an RS-232 receiver in parallel with 1000pF.
Data Cable Applications
The MAX3380E/MAX3381Es’ ±15kV ESD protection on
both the RS-232 I/Os as well as the logic I/Os makes
them ideal candidates for data cable applications. A
data cable is both an electrical connection and a level
translator, allowing ultra-miniaturization of cell phones
and other small portable devices.
Previous data cable approaches suffered from complexity due to the required protection circuits on both
the logic side of the cable, as well as on the RS-232
connections. The example shown in Figure 11 shows
the ease of using the MAX3380E/MAX3381E in data
cable applications. For best performance, keep the
logic level lines short and use the RS-232 level lines to
span any distance.
5V
T1IN
5V/div
0
5V
T1OUT
5V/div
0
-5V
5V
R1OUT
5V/div
0
1µs/div
VCC = VL = +4.2V, C1 = 0.1µF, C2 = C3 = C4 = 1µF,
CLOAD = 1000pF
Figure 9. Loopback Test Results at 460kbps (VCC = +4.2V)
VCC
C5
VCC
C1+
5V
V+
C1
C1-
C2
0
VL
C3
C2+
2V
T1IN
2V/div
MAX3380E
MAX3381E
VC4
C2-
0
-5V
2V
R1OUT
2V/div
0
TIME (1µs/div)
T_ OUT
T_ IN
T1OUT
5V/div
VCC = VL = +2.5V, C1 = 0.1µF, C2 = C3 = C4 = 1µF,
CLOAD = 1000pF
R_ IN
R_ OUT
5kΩ
FORCEON
VCC
FORCEOFF
Figure 10. Loopback Test Results at 460kbps (VCC = +2.5V)
1000pF
GND
Figure 8. Loopback Test Circuit
12
______________________________________________________________________________________
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
MAX3380E/MAX3381E
47µF 0.1µF
VCC
VL
FORCEOFF
0.1µF
FORCEON
V+
C1+
0.1µF
C10.1µF
V-
C2+
0.1µF
C2-
VBATT
MAX3380E/
MAX3381E
CELL PHONE
LOGIC LEVELS
PERIPHERALS
RS-232 LEVELS
Tx
T1IN
T1OUT
Tx
RTS
T2IN
T2OUT
CTS
Rx
R1OUT
R1IN
Rx
CTS
R2OUT
R2IN
RTS
I/O
INVALID
Figure 11. Typical Application Circuit
Pin Configuration
Chip Information
TRANSISTOR COUNT: 1467
PROCESS: BiCMOS
TOP VIEW
20 VCC
C1+ 1
V+ 2
19 FORCEOFF
C1- 3
18 GND
C2+ 4
C2- 5
V- 6
17 T1OUT
MAX3380E/
MAX3381E
INVALID 7
16 T2OUT
15 R1IN
14 R2IN
T1IN 8
13 VL
T2IN 9
12 FORCEON
R2OUT 10
11 R1OUT
TSSOP
______________________________________________________________________________________
13
MAX3380E/MAX3381E
+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
TSSOP.EPS
Package Information
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2001 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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