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PDF MAX3238ECAI Data sheet ( Hoja de datos )
| Número de pieza | MAX3238ECAI | |
| Descripción | +3.0V to +5.5V / 10nA / 250kbps RS-232 Transceivers with 15kV ESD-Protected I/O and Logic Pins | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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19-1632; Rev 1; 6/01
+3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
General Description
The MAX3238E/MAX3248E transceivers use Maxim’s
revolutionary AutoShutdown Plus™ feature to achieve
10nA supply current. These devices shut down the on-
board power supply and drivers when they do not sense
a valid signal transition on either the receiver or transmit-
ter inputs. This occurs if the RS-232 cable is disconnect-
ed or if the transmitters of the connected peripheral are
turned off. The devices turn on again when a valid transi-
tion is applied to any RS-232 receiver or transmitter input.
AutoShutdown Plus automatically achieves this power
savings through its on-board circuitry, as no changes are
required to the existing BIOS or operating system.
All RS-232 inputs and outputs, as well as the logic I/O
pins, have enhanced ESD protection to ±15kV. The addi-
tional ESD protection on the logic I/O pins makes the
MAX3238E/MAX3248E ideal for cell phone data cable
applications because it eliminates the need for costly
external TransZorb™ or protection schemes.
The MAX3238E/MAX3248E contain five drivers and three
receivers and are 3V-powered EIA/TIA-232 and V.28/V.24
communication interfaces intended for cell phones, data
cables, and modem applications. A proprietary, high-effi-
ciency, dual charge-pump power supply and a low-
dropout transmitter combine to deliver true RS-232
performance from a single +3.0V to +5.5V supply. A
guaranteed data rate of 250kbps provides compatibility
with popular software for communicating with personal
computers.
The MAX3238E and the MAX3248E differ only in their
input logic thresholds. The MAX3238E has standard logic
thresholds, while the MAX3248E has low-level logic
thresholds of 0.6V to 1.2V, which are ideal for 1.8V sys-
tems.
The transmitter inputs, FORCEON, and FORCEOFF have
a 400kΩ active positive feedback resistor. Once driven to
a valid logic level, they will retain this level if the driving
signal is removed or goes high impedance. Unused
transmitter and logic inputs may be left unconnected. The
MAX3238E/MAX3248E can operate with supply voltages
ranging from +3.0V to +5.5V.
Applications
Cellular Data Cables
Modems
Battery-Powered Equipment
Peripherals
Data Cradles
Printers
AutoShutdown Plus is a trademark of Maxim Integrated Products.
TransZorb is a trademark of General Semiconductor Industries, Inc.
†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; and other
patents pending.
Features
o Enhanced ESD Protection on RS-232 I/O Pins and
All Logic Pins
±15kV—Human Body Model
±8kV—IEC 1000-4-2 Contact Discharge
±15kV—IEC 1000-4-2 Air-Gap Discharge
o Guaranteed Data Rate: 250kbps
o 10nA Low-Power Shutdown with Receivers Active
o Schmitt Triggers on All Inputs
o Flow-Through Pinout
o Meets EIA/TIA-232 Specifications Down to 3.0V
o Guaranteed 6V/µs Slew Rate
o Low-Level Logic Thresholds (MAX3248E)
o RS-232-Compatible Outputs to 2.7V
Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX3238ECAI
0°C to +70°C
28 SSOP
MAX3238EEAI -40°C to +85°C
28 SSOP
MAX3248ECAI
0°C to +70°C
28 SSOP
MAX3248EEAI -40°C to +85°C
28 SSOP
Typical Operating Circuit appears at end of data sheet.
___________________Pin Configuration
TOP VIEW
C2+ 1
GND 2
C2- 3
V- 4
T1OUT 5
T2OUT 6
T3OUT 7
R1IN 8
R2IN 9
T4OUT 10
R3IN 11
T5OUT 12
FORCEON 13
FORCEOFF 14
MAX3238E
MAX3248E
SSOP
28 C1+
27 V+
26 VCC
25 C1-
24 T1IN
23 T2IN
22 T3IN
21 R1OUT
20 R2OUT
19 T4IN
18 R3OUT
17 T5IN
16 R1OUTB
15 INVALID
________________________________________________________________ Maxim Integrated Products 1
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 page  
+3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
Typical Operating Characteristics (continued)
(VCC = +3.3V, 250kbps data rate, 0.1µF capacitors, all transmitters loaded with 3kΩ, TA = +25°C, unless otherwise noted.)
TRANSMITTER OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
6
5 VOUT+
4
3
2
1 1 TRANSMITTER 250kbps
0
4 TRANSMITTERS 15.6kbps
ALL TRANSMITTERS LOADED
-1 WITH 3kΩ +1000pF
-2
-3
-4 VOUT-
-5
-6
2.0 2.5 3.0 3.5 4.0 4.5 5.0
SUPPLY VOLTAGE (V)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
50
40
30
20
10
0
2.0
1 TRANSMITTER 250kbps
4 TRANSMITTERS 15.6kbps
ALL TRANSMITTERS LOADED
WITH 3kΩ +1000pF
2.5 3.0 3.5 4.0 4.5
SUPPLY VOLTAGE (V)
5.0
______________________________________________________________Pin Description
PIN
1
2
3
4
5, 6, 7, 10, 12
8, 9, 11
13
NAME
C2+
GND
C2-
V-
T_OUT
R_IN
FORCEON
14 FORCEOFF
15
16
17, 19, 22, 23, 24
18, 20, 21
25
26
27
28
INVALID
R1OUTB
T_IN
R_OUT
C1-
VCC
V+
C1+
FUNCTION
Positive Terminal of Inverting Charge-Pump Capacitor
Ground
Negative Terminal of Inverting Charge-Pump Capacitor
-5.5V Generated by the Charge Pump
RS-232 Transmitter Outputs (T1OUT–T5OUT)
RS-232 Receiver Inputs (R1IN–R3IN)
Force-On Input. Drive high to override AutoShutdown Plus, keeping transmitters and
receivers on (FORCEOFF must be high) (Table 1). This pin has an active positive feedback
resistor. Once driven to a valid logic level, the pin retains that level if left unconnected until
power is cycled.
Force-Off Input. Drive low to shut down transmitters, receivers (except R1OUTB), and on-
board supply. This overrides AutoShutdown Plus and FORCEON (Table 1). This pin has an
active positive feedback resistor. Once driven to a valid logic level, the pin retains that
level if left unconnected until power is cycled.
Output of the Valid Signal Detector. A logic 1 indicates if a valid RS-232 level is present on
receiver inputs.
Noninverting Complementary Receiver Output. Always active.
TTL/CMOS Transmitter Inputs (T5IN–T1IN). This pin has an active positive feedback resis-
tor. Once driven to a valid logic level, the pin retains that level if left unconnected until
power is cycled.
TTL/CMOS Receiver Outputs (R3OUT–R1OUT)
Negative Terminal of Voltage-Doubler Charge-Pump Capacitor
+3.0V to +5.5V Supply Voltage
+5.5V Generated by the Charge Pump
Positive Terminal of Voltage-Doubler Charge-Pump Capacitor
_______________________________________________________________________________________ 5
5 Page 
+3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
5V/div
FORCEON =
FORCEOFF
T2OUT
T1IN
2V/div
T1OUT
T1OUT
4µs/div
VCC = 3.3V, C1–C4 = 0.1µF, RLOAD = 3kΩ, CLOAD = 2500pF
Figure 7. Transmitter Outputs when Recovering from Shutdown
or Powering Up
R1OUT
2µs/div
VCC = 3.3V, C1–C4 = 0.1µF, CLOAD = 1000pF
Figure 9. Loopback Test Result at 120kbps
+5V
0
+5V
0
-5V
+5V
0
VCC
VCC
C1+ V+
C1
C1-
C2+ MAX3238E V-
C2 MAX3248E
C2-
T_ IN
T_ OUT
R_ OUT
R_ IN
FORCEON
5kΩ
VCC FORCEOFF
GND
C3*
C4
1000pF
*C3 CAN BE RETURNED TO VCC OR GND.
Figure 8. Loopback Test Circuit
Transmitter Outputs when
Recovering from Shutdown
Figure 7 shows two transmitter outputs when recovering
from shutdown mode. As they become active, the out-
+5V
T1IN 0
T1OUT
R1OUT
+5V
0
-5V
+5V
0
2µs/div
VCC = 3.3V, C1–C4 = 0.1µF, CLOAD = 1000pF
Figure 10. Loopback Test Result at 250kbps
puts are shown going to opposite RS-232 levels (one
transmitter input is high, the other is low). Each trans-
mitter is loaded with 3kΩ in parallel with 2500pF. 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 MAX3238E/MAX3248E maintain the RS-232 ±5.0V
minimum transmitter output voltage even at high data
rates. Figure 8 shows a transmitter loopback test cir-
cuit. Figure 9 shows a loopback test result at 120kbps,
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet MAX3238ECAI.PDF ] | |
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