MAX3387ECUG+T [MAXIM]
Line Transceiver, 1 Func, 3 Driver, 3 Rcvr, PDSO24, 4.40 MM, 0.65 MM PITCH, TSSOP-24;
| 型号： | MAX3387ECUG+T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Line Transceiver, 1 Func, 3 Driver, 3 Rcvr, PDSO24, 4.40 MM, 0.65 MM PITCH, TSSOP-24 光电二极管 手机 |
| 文件： | 总16页 (文件大小：182K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
±9-±16±; Rev ±; ±0/99
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
MAX387E
General Description
Features
The MAX3387E 3V powered EIA/TIA-232 and V.28/V.24
is a communications interface with low power require-
ments, high data-rate capabilities, and enhanced elec-
trostatic discharge (ESD) protection. The MAX3387E
has three receivers and three transmitters. All RS-232
inputs and outputs are protected to ±±15V using the
IEC ±000-4-2 Air-Gap Discharge method, ±85V using
the IEC ±000-4-2 Contact Discharge method, and
±±15V using the ꢀuman ꢁodꢂ Model.
♦ V Pin for Compatibility with Mixed-Voltage
L
Systems
♦ ±15kV ESD Protection on Rx Inputs and Tx Outputs
♦ Low 300µA Supply Current
♦ Guaranteed 250kbps Data Rate
♦ 1µA AutoShutdown Plus™ with Receivers Active
♦ Meets EIA/TIA-232 Specifications Down to 3.0V
A proprietarꢂ low-dropout transmitter output stage
enables true RS-232 performance from a +3.0V to
+1.1V supplꢂ with a dual charge pump. The charge
pump requires onlꢂ four small 0.±µF capacitors for
operation from a +3.3V supplꢂ. The MAX3387E is capa-
ble of running at data rates up to 2105bps while main-
taining RS-232 compliant output levels.
Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX3387ECUG
MAX3387EEUG
0°C to +70°C
24 TSSOP
The MAX3387E has a unique V pin that allows interop-
L
-40°C to +81°C
24 TSSOP
eration in mixed-logic voltage sꢂstems. ꢁoth input and
output logic levels are pin programmable through the
V pin. The MAX3387E is available in a space-saving
L
TSSOP pac5age.
Typical Operating Circuit
Applications
Subnoteboo5/Palmtop Computers
PDAs and PDA Cradles
+3.3V
23
15
24
C
BYPASS
V
V
L
FORCEOFF
CC
2
6
1
3
4
5
C1+
V+
V-
C1
0.1µF
C3
0.1µF
Cell Phone Data Cables
C1-
C2+
ꢁatterꢂ-Powered Equipment
ꢀand-ꢀeld Equipment
MAX3387E
C2
0.1µF
C4
0.1µF
C2-
Peripherals
-in Configuration
7
8
T1OUT
T2OUT
T3OUT
T1IN
21
20
TTL/CMOS
INPUTS
T2IN
T3IN
RS-232
OUTPUTS
TOP VIEW
C1+
V+
1
2
3
4
5
6
7
8
9
24 FORCEOFF
23
19
18
10
V
CC
V
V
L
C1-
22 GND
14 R1OUT
13 R2OUT
R1IN
C2+
21 T1OUT
20 T2OUT
19 T3OUT
18 R1IN
17 R2IN
16 R3IN
MAX3387E
C2-
5k
L
V-
R2IN
TTL/CMOS
OUTPUTS
17
16
RS-232
INPUTS
T1IN
T2IN
INVALID
5k
V
L
12 R3OUT
R3IN
T3IN 10
FORCEON 11
R3OUT 12
15 V
L
9
5k
14 R1OUT
13 R2OUT
INVALID
FORCEON
11
GND
22
TSSOP
AutoShutdown Plus is a trademar5 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 1-800-835-8769.
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
ABSOLUTE MAXIMUM RATINGS
V
to GND..............................................................-0.3V to +6V
Short-Circuit Duration T_OUT to GND........................Continuous
CC
V to GND...................................................-0.3V to (V
L
+ 0.3V)
Continuous Power Dissipation (T = +70°C)
CC
A
V+ to GND................................................................-0.3V to +7V
V- to GND .................................................................+0.3V to -7V
V+ + V- (Note ±) .............................................................. +±3V
Input Voltages
T_IN, FORCEON, FORCEOFF to GND..................-0.3V to +6V
R_IN to GND .....................................................................±21V
Output Voltages
24-Pin TSSOP (derate 7.8mW/°C above +70°C) ..........621mW
Operating Temperature Ranges
MAX3387ECUG ...................................................0°C to +70°C
MAX3387EEUG ................................................-40°C to +81°C
Junction Temperature......................................................+±10°C
Storage Temperature Range.............................-61°C to +±10°C
Lead Temperature (soldering, ±0sec) .............................+300°C
T_OUT to GND...............................................................±±3.2V
MAX387E
R_OUT........................................................-0.3V to (V + 0.3V)
L
Note 1: V+ and V- can have maximum magnitudes of 7V, but their absolute difference cannot exceed ±3V.
Stresses beꢂond those listed under “Absolute Maximum Ratings” maꢂ cause permanent damage to the device. These are stress ratings onlꢂ, and functional
operation of the device at these or anꢂ other conditions beꢂond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods maꢂ affect device reliabilitꢂ.
DC ELECTRICAL CHARACTERISTICS
(V
CC
= V = +3.0V to +1.1V; C±–C4 = 0.±µF, tested at +3.3V ±±0ꢃ; C± = 0.047µF, C2–C4 = 0.33µF, tested at +1.0V ±±0ꢃ; T
=
L
A
T
to T , unless otherwise noted. Tꢂpical values are at V = V = +3.3V, T = +21°C.)
MAX CC L A
MIN
PARAMETER
DC CHARACTERISTICS (V
SYMBOL
= +3.3V or +1V, T = +21°C)
CONDITIONS
MIN
TYP
MAX
UNITS
CC
A
All R_IN idle, FORCEON = GND,
FORCEOFF = V , all T_IN idle
Supplꢂ Current, AutoShutdown
Plus
±.0
0.3
±0
±
µA
CC
Supplꢂ Current
mA
FORCEOFF = FORCEON = V , no load
CC
LOGIC INPUTS
V = 3.3V or 1.0V
0.8
0.6
L
T_IN, FORCEON,
FORCEOFF
Input Logic Threshold Low
Input Logic Threshold ꢀigh
V
V
V = 2.1V
L
V = 1.0V
L
2.4
2.0
±.4
V = 3.3V
L
T_IN, FORCEON,
FORCEOFF
V = 2.1V
L
V = ±.8V
L
0.9
0.1
Transmitter Input ꢀꢂsteresis
Input Lea5age Current
RECEIVER OUTPUTS
Output Voltage Low
V
±0.0±
±±
µA
T_IN, FORCEON, FORCEOFF
I
I
= ±.6mA
= -±mA
0.4
V
V
OUT
V -
L
0.6
V -
L
0.±
Output Voltage ꢀigh
OUT
RECEIVER INPUTS
Input Voltage Range
-21
0.8
0.6
+21
V
V
V = 1.0V
±.1
±.2
±.8
±.1
L
Input Threshold Low
Input Threshold ꢀigh
T
T
= +21°C
= +21°C
A
V = 2.1V or 3.3V
L
V = 1.0V
L
2.4
2.4
V
A
V = 2.1V or 3.3V
L
2
_______________________________________________________________________________________
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
MAX387E
DC ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= V = +3.0V to +1.1V; C±–C4 = 0.±µF, tested at +3.3V ±±0ꢃ; C± = 0.047µF, C2–C4 = 0.33µF, tested at +1.0V ±±0ꢃ; T
=
L
A
T
to T , unless otherwise noted. Tꢂpical values are at V = V = +3.3V, T = +21°C.)
MAX CC L A
MIN
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
0.1
1
MAX
UNITS
V
Input ꢀꢂsteresis
Input Resistance
T
A
= +21°C
3
7
5Ω
TRANSMITTER OUTPUTS
All transmitter outputs loaded with 35Ω to
ground
Output Voltage Swing
±1
±1.4
±0M
V
Output Resistance
V
V
= V+ = V- = 0, transmitter output = ±2V
= 0
300
Ω
CC
Output Short-Circuit Current
±60
±21
mA
_
T OUT
V
V
= ±±2V, transmitters disabled;
= 0 or 3.0V to 1.1V
_
CC
T OUT
Output Lea5age Current
µA
ESD PROTECTION
ꢀuman ꢁodꢂ Model
±±1
±±1
±8
R_IN, T_OUT
ESD Protection
5V
IEC ±000-4-2 Air-Gap Discharge method
IEC ±000-4-2 Contact Discharge method
AutoShutdown Plus (FORCEON = GND, FORCEOFF = V
)
CC
Positive threshold
Negative threshold
2.7
Receiver Input Threshold to
Figure 3a
V
V
INVALID Output ꢀigh
-2.7
-0.3
Receiver Input Threshold to
Figure 3a
0.3
0.4
INVALID Output Low
I
I
= -±.6mA
= -±.0mA
V
V
INVALID Output Voltage Low
INVALID Output Voltage ꢀigh
OUT
V - 0.6
L
OUT
Receiver Positive or Negative
Threshold to INVALID ꢀigh
t
V
CC
V
CC
V
CC
V
CC
= 1V, Figure 3b
= 1V, Figure 3b
= 1V, Figure 3b
= 1V, Figure 3b
±
µs
µs
INVꢀ
Receiver Positive or Negative
Threshold to INVALID Low
t
30
INVL
Receiver or Transmitter Edge to
Transmitters Enabled
t
±00
30
µs
WU
Receiver or Transmitter Edge to
Transmitters Shutdown
tAUTOSꢀDN
±1
60
sec
_______________________________________________________________________________________
3
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
TIMING CHARACTERISTICS
(V
to T
= V = +3V to +1.1V; C±–C4 = 0.±µF, tested at +3.3V ±±0ꢃ; C± = 0.047µF, C2–C4 = 0.33µF, tested at +1.0V ±±0ꢃ; T = T
CC
L
A
MIN
, unless otherwise noted. Tꢂpical values are at V
= V = +3.3V, T = +21°C.)
MAX
CC
L
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
R = 35Ω, C = ±000pF,
one transmitter switching
L
L
Maximum Data Rate
210
5bps
µs
t
t
0.±1
0.±1
±00
±00
10
PꢀL
Receiver input to receiver output,
C = ±10pF
L
Receiver Propagation Delaꢂ
PLꢀ
Time to Exit Shutdown
Transmitter S5ew
Receiver S5ew
V
> 3.7V
µs
ns
ns
T_OUT
MAX387E
t
t
- t
(Note 2)
PꢀL PLꢀ
- t
PꢀL PLꢀ
V
= 3.3V,
= +21°C,
CC
C = ±10pF to
L
±000pF
6
4
30
30
T
A
Transition-Region Slew
Rate
R = 35Ω to 75Ω,
measured from +3V
to -3V or -3V to +3V
V/µs
L
C = ±10pF to
L
2100pF
4
_______________________________________________________________________________________
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
MAX387E
Typical Operating Characteristics
(V
CC
= V = +3.3V, T = +21°C, unless otherwise noted.)
L
A
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
SLEW RATE vs. LOAD CAPACITANCE
16
14
12
10
8
7.5
5.0
2.5
DATA RATE = 250kbps
LOAD = 3kΩ IN PARALLEL WITH C
SLEW RATE -
SLEW RATE +
L
0
-2.5
-5.0
-7.5
6
4
2
0
0
1000
2000
3000
4000
5000
0
1000
2000
3000
4000
5000
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE
vs. DATA RATE
SUPPLY CURRENT vs. LOAD CAPACITANCE
60
50
40
7.5
5.0
2.5
LOAD = 3kΩ,
ONE TRANSMITTER
SWITCHING AT DATA
RATE, OTHER
LOAD = 3kΩ, 1000pF
ONE TRANSMITTER
SWITCHING AT DATA
RATE, OTHER
TRANSMITTERS
AT 1/8 DATA RATE
TRANSMITTERS
AT 1/8 DATA RATE
250kbps
120kbps
20kbps
30
20
10
0
0
-2.5
-5.0
-7.5
0
1000
2000
3000
4000
5000
0
50
100
150
200
250
LOAD CAPACITANCE (pF)
DATA RATE (kbps)
_______________________________________________________________________________________
5
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
-in Descriptions
PIN
±
NAME
C±+
V+
FUNCTION
Positive Terminal of the Voltage-Doubler Charge-Pump Capacitor
+1.1V Supplꢂ Generated bꢂ the Charge Pump
2
3
C±-
Negative Terminal of the Voltage-Doubler Charge-Pump Capacitor
Positive Terminal of the Inverting Charge-Pump Capacitor
Negative Terminal of the Inverting Charge-Pump Capacitor
-1.1V Generated bꢂ the Charge Pump
4
C2+
C2-
1
MAX387E
6
7
8
V-
T±IN
T2IN
TTL/CMOS Transmitter Inputs
Output of the Valid Signal Detector. INVALID is high if a valid RS-232 signal is present on
the receiver inputs.
9
INVALID
T3IN
±0
±±
TTL/CMOS Transmitter Inputs
Force-On Input. Drive high to override automatic circuitrꢂ 5eeping transmitters on
(FORCEOFF must be high) (Table ±).
FORCEON
±2
±3
±4
±1
±6
±7
±8
±9
20
2±
22
23
R3OUT
R2OUT
R±OUT
TTL/CMOS Receiver Outputs. Swing between 0 and V .
L
V
L
Logic-Level Supplꢂ. All CMOS inputs and outputs are referenced to this supplꢂ.
RS-232 Receiver Inputs
R3IN
R2IN
R±IN
T3OUT
T2OUT
T±OUT
GND
RS-232 Transmitter Outputs
Ground
V
CC
+3.0V to +1.1V Supplꢂ Voltage
Force-Off Input. Drive low to shut down transmitters and on-board power supplꢂ. This over-
rides all automatic circuitrꢂ and FORCEON (Table ±).
24
FORCEOFF
6
_______________________________________________________________________________________
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
MAX387E
These RS-232 output stages are turned off (high imped-
Detailed Description
ance) when the device is in shutdown mode. When the
Dual Chargeꢁ-ump
Voltage Converter
power is off, the MAX3387E permits the outputs to be
driven up to ±±2V.
The MAX3387E’s internal power supplꢂ consists of a
regulated dual charge pump that provides output volt-
ages of +1.1V (doubling charge pump) and -1.1V
(inverting charge pump), regardless of the input volt-
The transmitter inputs do not have pull-up resistors.
Connect unused inputs to GND or V .
L
Rꢀꢁ232 Receivers
age (V ) over a +3.0V to +1.1V range. The charge
CC
The receivers convert RS-232 signals to CMOS-logic
output levels. The MAX3387E’s receivers are alwaꢂs
active, even when the device is in shutdown.
pumps operate in a discontinuous mode: if the output
voltages are less than 1.1V, the charge pumps are
enabled; if the output voltages exceed 1.1V, the charge
pumps are disabled. Each charge pump requires a flꢂ-
ing capacitor (C±, C2) and a reservoir capacitor (C3,
C4) to generate the V+ and V- supplies.
The MAX3387E features an INVALID output that indi-
cates when no signal is present on anꢂ RS-232 receiver
inputs. INVALID is independent of other control logic
functions; it indicates the receiver input conditions onlꢂ
(Figures 2 and 3).
Rꢀꢁ232 Transmitters
The transmitters are inverting level translators that con-
vert CMOS-logic levels to 1.0V EIA/TIA-232 levels.
The MAX3387E transmitters guarantee a 2105bps data
rate with worst-case loads of 35Ω in parallel with
±000pF, providing compatibilitꢂ with PC-to-PC commu-
nication software (such as LapLin5™). Transmitters can
be paralleled to drive multiple receivers or mice. Figure ±
shows a complete sꢂstem connection.
+0.3V
R_IN
30µs
COUNTER
R
INVALID
-0.3V
FORCEON
POWER-
MANAGEMENT
UNIT OR
FORCEOFF
TRANSMITTERS ARE DISABLED, REDUCING SUPPLY CURRENT TO 1µA IF
ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR AT LEAST 30µs.
KEYBOARD
INVALID
CONTROLLER
I/O CHIP
V
L
Figure 2a. INVALID Function Diagram, INVALID = Low
POWER SUPPLY
MAX3387E
V
CC
+2.7V
R_IN
I/O
30µs
COUNTER
R
CHIP
WITH
UART
INVALID
RS-232
-2.7V
CPU
TRANSMITTERS ARE ENABLED IF:
ANY RECEIVER INPUT IS GREATER THAN +2.7V OR LESS THAN -2.7V;
ANY RECEIVER INPUT HAS BEEN BETWEEN +0.3V AND -0.3V FOR LESS THAN 30µs.
Figure 2b. INVALID Function Diagram, INVALID = ꢀigh
Figure ±. Interface Under Control of PMU
LapLin5 is a trademar5 of Traveling Software.
_______________________________________________________________________________________
7
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
TRANSMITTERS ENABLED, INVALID HIGH
EDGE
DETECT
T_IN
R_IN
FORCEOFF
+2.7V
INDETERMINATE
S
AUTOSHDN
30sec
TIMER
+0.3V
0V
EDGE
DETECT
AutoShutdown, TRANSMITTERS DISABLED,
1µA SUPPLY CURRENT, INVALID LOW
R
-0.3V
INDETERMINATE
MAX387E
FORCEON
-2.7V
TRANSMITTERS ENABLED, INVALID HIGH
Figure 2c. AutoShutdown Plus Logic
Figure 3a. Receiver Thresholds for INVALID
FORCEOFF states. Figure 2 and Table ± summarize the
MAX3387E’s operating modes. FORCEON and FORCE-
OFF override AutoShutdown Plus circuitrꢂ. When nei-
ther control is asserted, the IC selects between these
states automaticallꢂ based on the last receiver or trans-
mitter input edge received.
FORCEOFF
POWERDOWN
FORCEON
AUTOSHDN
ꢁꢂ connecting FORCEON to INVALID, the MAX3387E
shuts down when no valid receiver level and no receiver or
transmitter edge is detected for 30sec, and wa5es up
when a valid receiver level or receiver or transmitter
edge is detected.
POWERDOWN IS ONLY AN INTERNAL SIGNAL. IT CONTROLS THE
OPERATIONAL STATUS OF THE TRANSMITTERS AND THE POWER SUPPLIES.
ꢁꢂ connecting FORCEON and FORCEOFF to INVALID,
the MAX3387E shuts down when no valid receiver level
is detected.
Figure 2d. Power-Down Logic
Autoꢀhutdown -lus Mode
The MAX3387E achieves a±µA supplꢂ current with
Maxim’s AutoShutdown Plus feature, which operates
when FORCEOFF is high and a FORCEON is low. When
these devices do not sense a valid signal transition on
anꢂ receiver and transmitter input for 30sec, the on-
board charge pumps are shut down, reducing supplꢂ
current to ±µA. This occurs if the RS-232 cable is dis-
connected or if the connected peripheral transmitters
are turned off, and if the UART driving the transmitter
inputs is inactive. The sꢂstem turns on again when a
valid transition is applied to anꢂ RS-232 receiver or
transmitter input. As a result, the sꢂstem saves power
without changes to the existing ꢁIOS or operating sꢂs-
tem.
A mouse or other sꢂstem with AutoShutdown Plus maꢂ
need time to wa5e up. Figure 4 shows a circuit that
forces the transmitters on for ±00ms, allowing enough
time for the other sꢂstem to realize that the MAX3387E
is awa5e. If the other sꢂstem outputs valid RS-232 sig-
nal transitions within that time, the RS-232 ports on both
sꢂstems remain enabled.
V Logic ꢀupply Input
L
Unli5e other RS-232 interface devices where the receiv-
er outputs swing between 0 and V , the MAX3387E
CC
features a separate logic supplꢂ input (V ) that sets
L
V
for the receiver outputs and sets thresholds for the
Oꢀ
receiver inputs. This feature allows a great deal of flexi-
bilitꢂ in interfacing to manꢂ different tꢂpes of sꢂstems
with different logic levels. Connect this input to the host
Figures 2a and 2b show valid and invalid RS-232
receiver voltage levels. INVALID indicates the receiver
input’s condition, and is independent of FORCEON and
logic supplꢂ (±.8V ≤ V ≤ V ). Also, see the Tꢂpical
PDA/Cell-Phone Application section.
L
CC
8
_______________________________________________________________________________________
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
MAX387E
RECEIVER
INPUTS
INVALID
REGION
}
TRANSMITTER
INPUTS
TRANSMITTER
OUTPUTS
V
INVALID
OUTPUT
CC
0
t
INVL
t
INVH
t
AUTOSHDN
t
AUTOSHDN
t
t
WU
WU
V+
V
CC
0
V-
Figure 3b. AutoShutdown Plus/INVALID Timing Diagram
±±15V EꢀD -rotection
As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against electro-
static discharges (ESDs) encountered during handling
and assemblꢂ. The MAX3387E driver outputs and
receiver inputs have extra protection against static
electricitꢂ. Maxim has developed state-of-the-art struc-
tures to protect these pins against ESD of ±±15V with-
out damage. The ESD structures withstand high ESD in
all states: normal operation, shutdown, and powered
down. After an ESD event, Maxim’s “E” version devices
5eep wor5ing without latchup, whereas competing RS-
232 products can latch and must be powered down to
remove latchup. ESD protection can be tested in vari-
ous waꢂs. The transmitter outputs and receiver inputs
of this product familꢂ are characterized for protection to
the following limits:
POWER-
MASTER SHDN LINE
MANAGEMENT
0.1µF
1M
UNIT
FORCEOFF FORCEON
MAX3387E
Figure 4. AutoShutdown with Initial Turn-On to Wa5e Up a
Sꢂstem
ꢀoftwareꢁControlled ꢀhutdown
If direct software control is desired, INVALID can be
used to indicate a DTR or ring indicator signal. Connect
FORCEOFF and FORCEON together to bꢂpass
AutoShutdown so the line acts li5e a SHDN input.
±) ±±15V using the ꢀuman ꢁodꢂ Model
2) ±85V using the Contact-Discharge method specified
in IEC ±000-4-2
3) ±±15V using IEC ±000-4-2’s Air-Gap method
_______________________________________________________________________________________
9
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
Table 1. Output Control Truth Table
RECEIVER OR
VALID
TRANSMITTER
EDGE WITHIN
30sec
OPERATION STATUS
FORCEON
RECEIVER
LEVEL
T_OUT
R_OUT
FORCEOFF
Shutdown
(Forced Off)
X
±
0
0
0
±
±
±
X
X
X
X
X
X
ꢀigh-Z
Active
Active
ꢀigh-Z
Active
Active
Active
Active
Normal Operation
(Forced On)
MAX387E
Normal Operation
(AutoShutdown Plus)
Yes
No
Shutdown
(AutoShutdown Plus)
Normal Operation
Normal Operation
Shutdown
±
±
±
Yes
X
X
Active
Active
ꢀigh-Z
Active
Active
Active
INVALID
INVALID
INVALID
Yes
No
No
Normal Operation
(AutoShutdown)
Yes
No
X
X
Active
ꢀigh-Z
Active
Active
INVALID
INVALID
INVALID
INVALID
Shutdown
(AutoShutdown)
X = Don’t care
R
C
R
D
1M
1500Ω
I 100%
P
90%
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
I
r
DISCHARGE
RESISTANCE
CHARGE-CURRENT
LIMIT RESISTOR
AMPERES
HIGH-
VOLTAGE
DC
DEVICE
UNDER
TEST
36.8%
C
100pF
STORAGE
CAPACITOR
s
10%
0
SOURCE
TIME
0
t
RL
t
DL
CURRENT WAVEFORM
Figure 1a. ꢀuman ꢁodꢂ ESD Test Model
Figure 1b. ꢀuman ꢁodꢂ Current Waveform
EꢀD Test Conditions
ESD performance depends on a varietꢂ of conditions.
Contact Maxim for a reliabilitꢂ report that documents
test setup, methodologꢂ, and results.
Human Body Model
Figure 1a shows the ꢀuman ꢁodꢂ Model, and Figure
1b shows the current waveform it generates when dis-
charged into a low impedance. This model consists of a
±00pF capacitor charged to the ESD voltage of interest,
which is then discharged into the test device through a
±.15Ω resistor.
10 ______________________________________________________________________________________
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
MAX387E
R
R
D
C
50M to 100M
330Ω
I
100%
DISCHARGE
RESISTANCE
CHARGE-CURRENT
LIMIT RESISTOR
90%
HIGH-
VOLTAGE
DC
DEVICE
UNDER
TEST
C
s
150pF
STORAGE
CAPACITOR
SOURCE
10%
Figure 6a. IEC ±000-4-2 ESD Test Model
t
t
= 0.7ns to 1ns
R
IEC ±000ꢁ4ꢁ2
30ns
The IEC ±000-4-2 standard covers ESD testing and
performance of finished equipment; it does not specifi-
callꢂ refer to ICs. The MAX3387E helps ꢂou design
equipment that meets Level 4 (the highest level) of IEC
±000-4-2, without the need for additional ESD-protec-
tion components.
60ns
Figure 6b. IEC ±000-4-2 ESD Generator Current Waveform
Table 2. Minimum Required Capacitor
Values
The major difference between tests done using the
ꢀuman ꢁodꢂ Model and IEC ±000-4-2 is higher pea5
current in IEC ±000-4-2 because series resistance is
lower in the IEC ±000-4-2 model. ꢀence, the ESD with-
stand voltage measured to IEC ±000-4-2 is generallꢂ
lower than that measured using the ꢀuman ꢁodꢂ
Model. Figure 6a shows the IEC ±000-4-2 model, and
Figure 6b shows the current waveform for the ±85V IEC
±000-4-2 Level 4 ESD Contact Discharge test.
V
(V)
C1
(µF)
C2, C3, C4
(µF)
CC
3.0 to 3.6
4.1 to 1.1
3.0 to 1.1
0.±
0.047
0.22
0.±
0.33
±
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.
tors for 3.3V operation. For other supplꢂ voltages, see
Table 2 for required capacitor values. Do not use val-
ues smaller than those listed in Table 2. Increasing the
capacitor values (e.g., bꢂ a factor of 2) reduces ripple
on the transmitter outputs and slightlꢂ reduces power
consumption. C2, C3, and C4 can be increased without
changing C±’s value. ꢀowever, do not increase C±
without also increasing the values of C2, C3, and C4 to
maintain the proper ratios (C± to the other capacitors).
Machine Model
The Machine Model for ESD tests all pins using a
200pF storage capacitor and zero discharge resis-
tance. Its objective is to emulate the stress caused bꢂ
contact that occurs with handling and assemblꢂ during
manufacturing. All pins require this protection during
manufacturing, not just RS-232 inputs and outputs.
Therefore, after PC board assemblꢂ, the Machine
Model is less relevant to I/O ports.
When using the minimum required capacitor values,
ma5e sure the capacitor value does not degrade
excessivelꢂ with temperature. If in doubt, use capaci-
tors with a larger nominal value. The capacitor’s equiva-
lent series resistance (ESR), which usuallꢂ rises at low
temperatures, influences the amount of ripple on V+
and V-.
__________Applications Information
Capacitor ꢀelection
The capacitor tꢂpe used for C±–C4 is not critical for
proper operation; polarized or nonpolarized capacitors
can be used. The charge pump requires 0.±µF capaci-
______________________________________________________________________________________ 11
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
-owerꢁꢀupply Decoupling
In most circumstances, a 0.±µF bꢂpass capacitor is ade-
quate. In applications that are sensitive to power-supplꢂ
Operation Down to 2.7V
Transmitter outputs will meet EIA/TIA-162 levels of
±3.7V with supplꢂ voltages as low as +2.7V.
noise, decouple V
to ground with a capacitor of the
CC
Transmitter Outputs when
Exiting ꢀhutdown
same value as charge-pump capacitor C±. Connect
bꢂpass capacitors as close to the IC as possible.
Figure 7 shows two transmitter outputs when exiting
shutdown mode. As theꢂ become active, the two trans-
mitter outputs are shown going to opposite RS-232 lev-
els (one transmitter input is high; the other is low). Each
transmitter is loaded with 35Ω in parallel with 2100pF.
The transmitter outputs displaꢂ no ringing or undesir-
able transients as theꢂ come out of shutdown. Note that
the transmitters are enabled onlꢂ when the magnitude
of V- exceeds approximatelꢂ 3V.
5V/div
MAX387E
T2
2V/div
High Data Rates
The MAX3387E maintains the RS-232 ±1.0V minimum
transmitter output voltage even at high data rates.
Figure 8 shows a transmitter loopbac5 test circuit.
Figure 9 shows a loopbac5 test result at ±205bps, and
Figure ±0 shows the same test at 2105bps. For Figure
9, all transmitters were driven simultaneouslꢂ at
±205bps into RS-232 loads in parallel with ±000pF. For
Figure ±0, a single transmitter was driven at 2105bps,
and all transmitters were loaded with an RS-232 receiv-
er in parallel with ±000pF.
T1
V
= 3.3V
CC
C1–C4 = 0.1µF
50µs/div
Figure 7. Transmitter Outputs when Exiting Shutdown
Interconnection with
3V and 1V Logic
V
CC
0.1µF
The MAX3387E can directlꢂ interface with various 1V
logic families, including ACT and ꢀCT CMOS. The logic
voltage power-supplꢂ pin (V ) sets the output voltage
L
level of the receivers and the input thresholds of the
transmitters.
V
CC
C1+
V+
V-
C3
C4
C1
MAX3387E
C1-
C2+
C2
C2-
5V/div
T_ OUT
T_ IN
T1IN
R_ IN
5k
R_ OUT
5V/div
T1OUT
1000pF
FORCEOFF
FORCEON
V
5V/div
CC
R1OUT
GND
V
CC
= 3.3V
2µs/div
Figure 9. Loopbac5 Test Results at ±205bps
Figure 8. Loopbac5 Test Circuit
12 ______________________________________________________________________________________
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
MAX387E
The ring indicate (RI) signal is generated when a PDA,
phone, or other “cradled” device is plugged into its cradle.
This generates a logic-low signal to the RI transmitter
input, creating +6V at the ring indicate pin. The PC’s
UART RI input is the onlꢂ pin that can generate an inter-
rupt from signals arriving through the RS-232 port. The
interrupt routine for this UART will then service the RS-
232 full-duplex communication between the PDA and
the PC.
5V/div
5V/div
5V/div
T1IN
T1OUT
R1OUT
As cell phone design becomes more li5e that of PDAs,
cell phones will require similar doc5ing abilitꢂ and com-
munication protocol. Cell phones operate on a single
lithium-ion (Li+) batterꢂ and wor5 with a power-supplꢂ
voltage of +2.7V to +4V. The baseband logic coming
from the phone connector can be as low as ±.8V at the
transceivers. To prevent forward biasing of a device
internal to the cell phone, the MAX3387E comes with a
V
CC
= 3.3V
2µs/div
Figure ±0. Loopbac5 Test Results at 2105bps
logic power-supplꢂ pin (V ) that limits the logic levels
L
presented to the phone. The receiver outputs will sin5
to zero for low outputs, but will not exceed V for logic
L
Typical -DA/Cellꢁ-hone Application
The MAX3387E is designed with PDA applications in
mind. Two transmitters and two receivers handle stan-
dard full-duplex communication protocol, while an extra
transmitter allows a ring indicator signal to alert the
UART on the PC. Without the ring indicator transmitter,
solutions for these applications would require software-
intensive polling of the cradle inputs.
highs. The input logic levels for the transmitters are also
altered, scaled bꢂ the magnitude of the V input. The
L
device will wor5 with V as low as ±.8V before the
L
charge-pump noise will begin to cause the transmitter
outputs to oscillate. This is useful with cell phones and
other power-efficient devices with core logic voltage
levels that go as low as ±.8V.
Chip Information
TRANSISTOR COUNT: ±267
______________________________________________________________________________________ 13
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
-ac5age Information
MAX387E
14 ______________________________________________________________________________________
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
MAX387E
NOTES
______________________________________________________________________________________ 15
3V, ±±15V EꢀDꢁ-rotected, Autoꢀhutdown -lus
Rꢀꢁ232 Transceiver for -DAs and Cell -hones
NOTES
MAX387E
Maxim cannot assume responsibilitꢂ for use of anꢂ circuitrꢂ other than circuitrꢂ entirelꢂ embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitrꢂ and specifications without notice at anꢂ time.
16 ____________________Maxim Integrated -roducts, ±20 ꢀan Gabriel Drive, ꢀunnyvale, CA 94086 408ꢁ737ꢁ7600
© ±999 Maxim Integrated Products
Printed USA
is a registered trademar5 of Maxim Integrated Products.
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