Page 1
现货库存、技术资料、百科信息、热点资讯，精彩尽在鼎好!
General Description
The MAX3388E/MAX3389E are 2.5V-powered EIA/TIA232 and V.28/V.24 communications interfaces with low
power requirements, high data-rate capabilities, and
enhanced electrostatic discharge (ESD) protection. The
MAX3388E/MAX3389E have two receivers and three
transmitters. All RS-232 inputs and outputs are protected
to ±15kV using the IEC 1000-4-2 Air-Gap Discharge
method, ±8kV using the IEC 1000-4-2 Contact Discharge
method, and ±15kV using the Human Body Model.
In addition to the traditional RS-232 I/O, these devices have
dedicated logic-level I/O pins for additional device-todevice handshaking. During shutdown the logic-level I/O
pins are active for the MAX3389E. An internal 62Ω switch is
provided to switch power to external circuitry or modules.
A proprietary low-dropout transmitter output stage
enables RS-232 compatible performance from a +2.35V
to +3.0V supply with a dual charge pump. The charge
pump requires only four small 0.1µF capacitors for operation from a +2.5V supply. The MAX3388E/MAX3389E
are capable of running at data rates up to 460kbps while
maintaining RS-232-compatible output levels.
The MAX3388E/MAX3389E have a unique V
L
pin that
allows interoperation in mixed-logic voltage systems.
Both input and output logic levels are pin programmable through the V
L
pin. The MAX3388E/MAX3389E are
available in a space-saving TSSOP package.
Features
♦ VLPin for Compatibility with Mixed-Voltage
Systems
♦ Additional I/O for Hot-Sync Applications
♦ ±15kV ESD Protection on Rx Inputs, Tx Outputs,
LIN, and SWIN
♦ Low 300µA Supply Current
♦ Guaranteed 460kbps Data Rate
♦ 1µA Low-Power Shutdown
♦ Integrated Switch for Powering Remote Circuitry
♦ Flow-Through Pinout
♦ L
OUT
Active During Shutdown (MAX3389E)
Applications
Subnotebook/Palmtop Computers
PDAs and PDA Cradles
Cell Phone Data Cables
Battery-Powered Equipment
Hand-Held Equipment
Peripherals
MAX3388E/MAX3389E
2.5V, ±15kV ESD-Protected RS-232
Transceivers for PDAs and Cell Phones
________________________________________________________________ Maxim Integrated Products 1
Typical Operating Circuit
19-1845; Rev 1; 9/01
Pin Configuration
Ordering Information
Covered by U.S Patent numbers 4,636,930; 4,679,134;
4,777,577; 4,797,899; 4,809,152; 4,897,774; 4,999,761.
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.
C3
0.1µF
C4
0.1µF
RS-232
I/O
+2.5V
C
BYPASS
C1
0.1µF
C2
0.1µF
= ±15kV ESD PROTECTION
1
C1+
3
C1-
4
C2+
5
C2-
7
T1IN
T2IN
8
T3IN
9
13
R1OUT
R2OUT12
10 LOUT
11
SWOUT
24
SHDN
MAX3388E
MAX3389E
SHDN
23
V
CCVL
GND
22
14
2
V+
6
V-
T1OUT
21
T2OUT
20
T3OUT
R1IN
5kΩ
R2IN
5kΩ
30kΩ
SWIN
19
18
17
LIN
16
15
V
L
V
L
PART TEMP. RANGE PIN-PACKAGE
MAX3388ECUG
MAX3388EEUG -40°C to +85°C 24 TSSOP
MAX3389ECUG
MAX3389EEUG -40°C to +85°C 24 TSSOP
0°C to +70°C 24 TSSOP
0°C to +70°C 24 TSSOP
TOP VIEW
C1+
C1-
C2-
T1IN
T3IN
LOUT
SWOUT
1
2
V+
3
4
MAX3388E
5
MAX3389E
6
V-
7
8
9
10
11
12
24
SHDN
23
V
CC
22
GND
21
T1OUTC2+
20
T2OUT
19
T3OUT
18
R1IN
17
R2INT2IN
16
LIN
15
SWIN
14
V
L
R1OUTR2OUT
13
TSSOP
Page 2
MAX3388E/MAX3389E
2.5V, ±15kV ESD-Protected RS-232
Transceivers for PDAs and Cell Phones
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
DC ELECTRICAL CHARACTERISTICS
(VCC= VL= +2.35V to +3.0V, C1–C4 = 0.1µF, TA= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at VCC= VL= +2.5V,
T
A
= +25°C.)
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.
Note 1: V+ and V- can have maximum magnitudes of 7V, but their absolute difference cannot exceed 13V.
V
CC
to GND..............................................................-0.3V to +6V
V
L
to GND...................................................-0.3V to (VCC+ 0.3V)
V+ to GND ................................................................-0.3V to +7V
V- to GND .................................................................+0.3V to -7V
V+ +V-(Note 1) ............................................................... +13V
Input Voltages
T_IN, SHDN, LIN to GND.......................................-0.3V to +6V
R_IN to GND .....................................................................±25V
SWIN to GND...........................................-0.3V to (V
CC
+ 0.3V)
Output Voltages
T_OUT to GND...............................................................±13.2V
R_OUT, SWOUT, LOUT to GND ................-0.3V to (V
L
+ 0.3V)
Short-Circuit Duration T_OUT to GND........................Continuous
Continuous Power Dissipation (T
A
= +70°C)
24-Pin TSSOP (derate 12.2mW/°C above +70°C) ........975mW
Operating Temperature Ranges
MAX338_ECUG ...................................................0°C to +70°C
MAX338_EEUG.................................................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER
SYMBOL
Shutdown Supply Current
Supply Current
Input Logic Low
Input Logic High
Transmitter Input Hysteresis
Input Leakage Current
Output Leakage Current
Output Voltage Low
Output Voltage High
Input Voltage Range
Input Threshold Low
Input Threshold High
Input Hysteresis
Input Resistance TA= +25°C
I
OUT
= -1mA
I
OUT
= 1.6mA
R_OUT, SHDN = 0
VL= +2.5V
VL= +2.5V
SHDN = VCC, no load
SHDN = GND, all inputs at GND
CONDITIONS MIN TYP MAX
110
0.3 1
UNITS
µA
mA
0.6 V
1.5 V
0.4 V
µA±0.01 ±1
µA±0.05 ±10
0.4 V
VL- VL-
0.6 0.13
V
-25 +25 V
0.6 1.1 V
V1.8 2.4
V
kΩ
0.7
357
All transmitter outputs loaded with 3kΩ to
ground
Output Voltage Swing ±3.7 ±4.2
Output Resistance VCC= 0, transmitter output = ±2V Ω300 10M
Output Short-Circuit Current V
T_OUT
= 0 mA±60
DC CHARACTERISTICS (VCC= +2.5V, TA= +25°C)
LOGIC INPUTS (T_IN, SHDN)
RECEIVER OUTPUTS
RECEIVER INPUTS
TRANSMITTER OUTPUTS
V
TA= +25°C, VL= +2.5V
TA= +25°C, VL= +2.5V
Page 3
MAX3388E/MAX3389E
2.5V, ±15kV ESD-Protected RS-232
Transceivers for PDAs and Cell Phones
_______________________________________________________________________________________ 3
TIMING CHARACTERISTICS
(VCC= VL= +2.35V to +3.0V, C1–C4 = 0.1µF, TA= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at VCC= VL= +2.5V,
T
A
= +25°C.)
t
PHL
- t
PLH
Note 2: Guaranteed by correlation.
Note 3: Transmitter skew is measured at the transmitter zero crosspoint.
DC ELECTRICAL CHARACTERISTICS (continued)
(VCC= VL= +2.35V to +3.0V, C1–C4 = 0.1µF, TA= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at VCC= VL= +2.5V,
T
A
= +25°C.)
PARAMETER
Maximum Data Rate
Receiver Propagation Delay
Receiver Output Enable Time
Receiver Output Disable Time
Time to Exit Shutdown
Transmitter Skew
Receiver Skew
Transition-Region Slew
Rate
t
PHL
- t
PLH
t
PLH
t
PHL
SYMBOL CONDITIONS
RL= 3kΩ, CL= 1000pF,
one transmitter switching
Receiver input to receiver output,
C
L
= 150pF
V
T_OUT
> 3.7V
RL= 3kΩ, CL= 1000pF (Note 3)
VCC= +2.5V, TA= +25°C,
RL= 3kΩ to 7kΩ,
measured from +3V
to -3V or -3V to +3V,
one transmitter switching
CL= 150pF to
1000pF
CL= 150pF to
2500pF
430
630
50
100
30
200
200
0.15
0.15
250
MIN TYP MAX UNITS
kbps
µs
ns
ns
µs
ns
ns
V/µs
RL= 3kΩ, CL= 150pF,
one transmitter switching (Note 2)
460
t
PHL
- t
PLH
Output Leakage Current
HANDSHAKING I/O (LIN, LOUT)
Input Voltage Range 0V
Input Threshold Low LIN, VL = +2.5V, TA = +25°C 0.6 1.1 V
Input Threshold High LIN, VL = +2.5V, TA = +25°C 1.7 2 V
Input Hysteresis 0.6 V
Input Resistance TA = +25oC2040kΩ
Output Voltage Low LOUT, I
Output Leakage Current LOUT = VL, LIN = low or float ±10 µA
SWITCH (SWIN, SWOUT)
Input Voltage Range 0V
On-Resistance 62 100 Ω
Off-Leakage Current SHDN = 0 ±1µA
Turn-On Time 0.18 µs
Turn-Off Time 0.7 µs
ESD PROTECTION
R_IN, T_OUT, LIN, SWIN
ESD Protection
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
V
V
Human Body Model ±15
IEC 1000-4-2 Air-Gap Discharge method ±15
IEC 1000-4-2 Contact Discharge method ±8
= ±12V, transmitters disabled,
T_OUT
= 0 or +2.5V
CC
SINK
= 1.6mA 0.4 V
±25 µA
CC
CC
kV
V
V
Page 4
MAX3388E/MAX3389E
2.5V, ±15kV ESD-Protected RS-232
Transceivers for PDAs and Cell Phones
4 _______________________________________________________________________________________
Typical Operating Characteristics
(VCC= VL= +2.5V, TA = +25°C, unless otherwise noted.)
-5.0
-2.5
2.5
0
5.0
0 20001000 3000 4000 5000
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
MAX3388E toc01
LOAD CAPACITANCE (pF)
OUTPUT VOLTAGE (V)
DATA RATE = 460kbps
LOAD = 3kΩ IN PARALLEL
0
2
4
6
8
10
12
14
16
0 1000 2000 3000 4000 5000
SLEW RATE vs. LOAD CAPACITANCE
MAX3386E toc02
LOAD CAPACITANCE (pF)
SLEW RATE (V/µs)
SLEW RATE +
SLEW RATE -
-5.0
-2.5
2.5
0
5.0
0 100
150 200 250
50 300 350 400 450
TRANSMITTER OUTPUT VOLTAGE
vs. DATA RATE
MAX3388E toc03
DATA RATE (kbps)
OUTPUT VOLTAGE (V)
LOAD = 3kΩ, 1000pF
ONE TRANSMITTER SWITCHING
AT DATA RATE, OTHER
TRANSMITTERS AT 1/8
DATA RATE
0
20
10
40
30
50
60
0 20001000 3000 4000 5000
SUPPLY CURRENT
vs. LOAD CAPACITANCE
MAX3388E toc04
LOAD CAPACITANCE (pF)
SUPPLY CURRENT (mA)
LOAD = 3kΩ
ONE TRANSMITTER SWITCHING
AT DATA RATE, OTHER
TRANSMITTERS AT 1/8
DATA RATE
460kbps
240kbps
20kbps
1V/div
LOUT
LIN
R
PULLUP
LIN TO LOUT t
= 1kΩ
200ns/div
ON-RESISTANCE
PD
MAX3388E toc05
70
65
60
(Ω)
ON
R
55
50
45
0 1.00.5 1.5 2.0 2.5
vs. SWIN VOLTAGE
TA = +85°C
TA = +25°C
TA = -40°C
V
(V)
SWIN
MAX3388E toc06
Page 5
MAX3388E/MAX3389E
2.5V, ±15kV ESD-Protected RS-232
Transceivers for PDAs and Cell Phones
_______________________________________________________________________________________ 5
Pin Description
PIN NAME FUNCTION
1 C1+ Positive Terminal of the Voltage-Doubler Charge-Pump Capacitor
2 V+ +4.2V Supply Generated by the Charge Pump
3 C1- Negative Terminal of the Voltage-Doubler Charge-Pump Capacitor
4 C2+ Positive Terminal of the Inverting Charge-Pump Capacitor
5 C2- Negative Terminal of the Inverting Charge-Pump Capacitor
6 V- -4.2V Supply Generated by the Charge Pump
7, 8, 9
10 LOUT Handshaking Output. This output is active during shutdown for the MAX3389E.
11 SWOUT Switch Output
12, 13
14 V
15 SWIN Switch Input.
16 LIN Handshaking Input. This input is active during shutdown for the MAX3389E.
17, 18
19, 20, 21
22 GND Ground
23 V
24 SHDN Shutdown Input. 0 = shutdown, switch open; 1 = normal operation, switch closed.
T1IN,
T2IN, T3IN
R2OUT,
R1OUT
L
R2IN,
R1IN
T3OUT,
T2OUT,
T1OUT
CC
CMOS Transmitter Inputs
CMOS Receiver Outputs. Swing between 0 and VL.
Logic-Level Supply. All CMOS inputs and outputs are referred to this supply. VL = +1.8V to +3.0V.
RS-232 Receiver Inputs
RS-232 Transmitter Outputs
+2.35V to +3V Supply Voltage
Page 6
MAX3388E/MAX3389E
2.5V, ±15kV ESD-Protected RS-232
Transceivers for PDAs and Cell Phones
6 _______________________________________________________________________________________
Detailed Description
Dual Charge-Pump
Voltage Converter
The MAX3388E/MAX3389E’s internal power supply
consists of a regulated dual charge pump that provides
output voltages of +4.2V (doubling charge pump) and -
4.2V (inverting charge pump), regardless of the input
voltage (VCC) over a +2.5V to +3.0V range. The charge
pumps operate in a discontinuous mode: if the output
voltages are less than 4.2V, the charge pumps are
enabled; if the output voltages exceed 4.2V, the charge
pumps are disabled. Each charge pump requires flying
capacitors (C1, C2) and reservoir capacitors (C3, C4)
to generate the V+ and V- supplies.
RS-232 Transmitters
The transmitters are inverting level translators that convert
CMOS-logic levels to ±3.7V EIA/TIA-232-compatible
levels.
The MAX3388E/MAX3389E’s transmitters guarantee a
250kbps data rate with loads of 3kΩ in parallel with
1000pF and 460kbps data rate with loads of 3kΩ in parallel with 150pF. Figure 1 shows a complete system connection.
These RS-232 output stages are turned off (high
impedance) when the devices are in shutdown mode.
When the power is off, the MAX3388E/MAX3389E permit
the outputs to be driven up to ±12V.
The transmitter inputs do not have pullup resistors.
Connect unused inputs to GND or VL.
RS-232 Receivers
The receivers convert RS-232 signals to CMOS-logic
output levels. The MAX3388E/MAX3389E’s receivers
have inverting outputs. The outputs are high impedance in shutdown.
Shutdown Mode
Supply current falls to less than 1µA when the
MAX3388E/MAX3389E are placed in shutdown mode
(SHDN logic low). When shut down, the device’s charge
pumps are turned off, V+ decays to VCC, V- is pulled to
ground, the switch is opened, and the transmitter outputs
are disabled (high impedance). The time required to exit
Figure 1. Interface Under Control of PMU
Figure 2. Transmitter Outputs when Exiting Shutdown
Table 1. Shutdown Logic Truth Table
LOUT
SHDN
T R AN SM IT T ER
O U TPU T S
RECEIVER
OUTPUTS
CH ARG E
PU M P
SWIT C H
MAX3388E MAX3389E
L High-Z High-Z Inactive Open High-Z
LIN
H Active Active Active Closed
LIN LIN
POWER-
MANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER
I/O CHIP
POWER SUPPLY
SHDN
V
L
MAX3388E
MAX3389E
5V/div
2V/div
T1
I/O
CPU
CHIP
WITH
UART
RS-232
VCC = +2.5V
C1–C4 = 0.1µF
= 1000pF, RL = 3kΩ
C
L
10µs/div
T2
Page 7
MAX3388E/MAX3389E
2.5V, ±15kV ESD-Protected RS-232
Transceivers for PDAs and Cell Phones
_______________________________________________________________________________________ 7
shutdown is typically 30µs, as shown in Figure 2.
Connect SHDN to VCCif the shutdown mode is not used.
In shutdown mode, the receiver outputs are high impedance (Table 1).
VLLogic Supply Input
Unlike other RS-232 interface devices where the receiver
outputs swing between 0 and VCC, the MAX3388E/
MAX3389E feature a separate logic supply input (VL)
that sets VOHfor the receiver outputs and sets thresholds for the transmitter inputs. This feature allows a
great deal of flexibility in interfacing to many different
types of systems with different logic levels. Connect
this input to the host logic supply (1.8V ≤ V
L
≤ VCC).
Also see the Typical PDA/Cell-Phone Application section.
±15kV ESD Protection
As with all Maxim devices, ESD-protection structures are
incorporated on all pins to protect against ESDs encountered during handling and assembly. The MAX3388E/
MAX3389E’s driver outputs, receiver inputs, the handshaking input LIN, and the switch terminal SWIN have
extra protection against static electricity. 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 powered down. After an ESD event,
Maxim’s “E” version devices keep working without
latchup, 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 outputs and receiver inputs of this product family are
characterized for protection to the following limits:
1) ±15kV using the Human Body Model
2) ±8kV using the Contact Discharge method specified
in IEC 1000-4-2
3) ±15kV using IEC 1000-4-2’s Air-Gap Discharge
method
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 3a shows the Human Body Model, and Figure 3b
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 MAX3388E/MAX3389E helps 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 voltage measured to IEC 1000-4-2 is generally
lower than that measured using the Human Body
Model. Figure 4a shows the IEC 1000-4-2 model, and
Figure 4b shows the current waveform for the ±8kV IEC
1000-4-2 Level 4 ESD Contact Discharge test.
Figure 3a. Human Body ESD Test Model
Figure 3b. Human Body Current Waveform
R
C
1MΩ
CHARGE-CURRENT
LIMIT RESISTOR
HIGH-
VOLTAGE
DC
SOURCE
IP 100%
90%
AMPERES
36.8%
10%
0
C
s
100pF
0
t
RL
R
D
1500Ω
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
I
r
TIME
t
DL
CURRENT WAVEFORM
DEVICE
UNDER
TEST
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
Page 8
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.
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 2.5V operation (Table 2). 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, and C4 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 larger nominal value. The capacitor’s equivalent
series resistance (ESR), which usually rises at low temperatures, influences the amount of ripple on V+ and V-.
Power-Supply Decoupling
In most circumstances, a 0.1µF bypass capacitor is
adequate. In applications that are sensitive to powersupply noise, decouple VCCto 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
Exiting Shutdown
Figure 2 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 2.5V.
MAX3388E/MAX3389E
2.5V, ±15kV ESD-Protected RS-232
Transceivers for PDAs and Cell Phones
8 _______________________________________________________________________________________
Figure 4a. IEC 1000-4-2 ESD Test Model
Figure 4b. IEC 1000-4-2 ESD Generator Current Waveform
Table 2. Minimum Required Capacitor
Values
V
CC
(V)
C1–C4
(µF)
2.5 to 3.0 0.1
R
C
50MΩ to 100MΩ
CHARGE-CURRENT
LIMIT RESISTOR
HIGH-
VOLTAGE
DC
SOURCE
100%
90%
C
s
150pF
I
RD
330Ω
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
DEVICE
UNDER
TEST
PEAK
I
10%
tR = 0.7ns to 1ns
30ns
60ns
t
Page 9
MAX3388E/MAX3389E
2.5V, ±15kV ESD-Protected RS-232
Transceivers for PDAs and Cell Phones
High Data Rates
The MAX3388E/MAX3389E maintain RS-232-compatible
transmitter output voltages even at high data rates. Figure
5 shows a transmitter loopback test circuit. Figure 6 shows
a loopback test result at 250kbps, and Figure 7 shows the
same test at 460kbps. For Figure 6, all transmitters were
driven simultaneously at 250kbps into RS-232 loads in
parallel with 1000pF. For Figure 7, a single transmitter was
driven at 460kbps, and all transmitters were loaded with
an RS-232 receiver in parallel with 150pF.
Power Switch
The MAX3388E/MAX3389E contain an internal switch
for powering external circuitry. This can be used to
power hot-sync circuitry or other low-power circuitry.
The switch on- resistance is typically 62Ω. The SWIN
side of the switch is ESD protected to ±15kV.
Logic-Level I/O
In addition to the traditional RS-232 I/O, the
MAX3388E/MAX3389E have a logic-level transceiver
from the RS-232 connector side to the CMOS-logic
side. The input impedance is typically 30kΩ, and the
output is open drain. The logic level I/O is active during
shutdown for the MAX3389E.
This I/O transceiver is useful for hot syncing or other
dedicated communication capability. The input is ESD
protected to ±15kV.
Typical PDA/Cell-Phone Application
The MAX3388E/MAX3389E designed with PDA applications in mind. Two transmitters and two receivers handle
standard full-duplex communication protocol, while an
extra transmitter allows a ring indicator (RI) 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.
The RI signal is generated when a PDA, cellular phone, or
other “cradled” device is plugged into its cradle. This
generates a logic-low signal to RI transmitter input, creating +3.7V at the ring indicate pin. The PC’s UART RI input
is the only pin that can generate an interrupt 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.
As cell phone design becomes more like that of PDAs,
cell phones will require similar docking ability and communication protocol. Cell phones operate on a single
lithium-ion (Li+) battery and generate a regulated output voltage of +2.35V to +3V from the phone connector.
The baseband logic coming from the phone connector
can be as low as 1.8V at the transceivers. To prevent
forward biasing of a device internal to the cell phone,
the MAX3388E/MAX3389E come with a logic powersupply pin (V
L
) that limits the logic levels presented to
Figure 5. Loopback Test Circuit
Figure 6. Loopback Test Results at 250kbps
_______________________________________________________________________________________ 9
C1
C2
V
CC
0.1µF
V
C1+
C1-
C2+
C2-
T_ IN
R_ OUT
V
CC
SHDN
CC
MAX3388E
MAX3389E
GND
V+
V-
T_ OUT
R_ IN
5kΩ
C3
C4
C
L
T1IN
T1OUT
R1OUT
CL = 1000pF
1µs/div
2V/div
5V/div
5V/div
Page 10
the phone. The receiver outputs will sink to zero for low
outputs, but will not exceed VLfor logic highs. The
input logic levels for the transmitters are also altered,
scaled by the magnitude of the VLinput. The devices
will work with VLas low as 1.8V. This is useful with cell
phones and other power-efficient devices with core
logic voltage levels that go as low as 1.8V.
Chip Information
TRANSISTOR COUNT: 1323
MAX3388E/MAX3389E
2.5V, ±15kV ESD-Protected RS-232
Transceivers for PDAs and Cell Phones
10 ______________________________________________________________________________________
Figure 7. Loopback Test Results at 460kbps
T1IN
T1OUT
R1OUT
CL = 150pF
1µs/div
2V/div
5V/div
5V/div
Page 11
MAX3388E/MAX3389E
2.5V, ±15kV ESD-Protected RS-232
Transceivers for PDAs and Cell Phones
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________11
© 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
TSSOP.EPS
Loading...