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PDF ISL4244E Data sheet ( Hoja de datos )
| Número de pieza | ISL4244E | |
| Descripción | QFN Packaged/ 15kV ESD Protected/ +2.7V to +5.5V/ 10Nanoamp/ 250kbps/ 1Mbps/ RS-232 Transceivers with Enhanced Automatic Powerdown | |
| Fabricantes | Intersil Corporation | |
| Logotipo |  |
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Data Sheet
ISL4238E, ISL4244E, ISL4245E
November 2002
FN8038.2
QFN Packaged, ±15kV ESD Protected,
+2.7V to +5.5V, 10Nanoamp, 250kbps/
1Mbps, RS-232 Transceivers with
Enhanced Automatic Powerdown
The Intersil ISL4238E/44E/45E devices are 2.7V to 5.5V
powered RS-232 transmitters/receivers which meet
ElA/TIA-232 and V.28/V.24 specifications, even at
VCC = 3.0V. Additionally, they provide ±15kV ESD protection
(IEC6100-4-2 Air Gap and Human Body Model) on
transmitter outputs and receiver inputs (RS-232 pins).
Targeted applications are PDAs, Palmtops, and notebook
and laptop computers where the low operational, and even
lower standby, power consumption is critical. Efficient on-
chip charge pumps, coupled with manual and enhanced
automatic powerdown functions, reduce the standby supply
current to a 10nA trickle. Tiny 5mm x 5mm Quad Flat No-
Lead (QFN) packaging and the use of small, low value
capacitors ensure board space savings as well. Data rates
greater than 250kbps (ISL4238E/44E) / 1Mbps (ISL4245E)
are guaranteed at worst case load conditions.
The ISL424XE are 3 driver, 5 receiver (DTE) devices that,
coupled with the QFN package, provide the industry’s
smallest, lowest power complete serial port suitable for
PDAs, and laptop or notebook computers. The 5x5 QFN
requires 60% less board area than a 28 lead TSSOP, and is
nearly 20% thinner. The devices also include a noninverting
always-active receiver for “wake-up” capability.
The ISL4238E is a 5 driver, 3 receiver device optimized for
DCE applications with full hardware handshaking. It also
includes a noninverting always-active receiver for RING
INDICATOR monitoring. Transmitter and logic inputs include
active feedback resistors that retain the input state once
driven to a valid logic level.
These devices feature an enhanced automatic
powerdown function which powers down the on-chip power-
supply and driver circuits. This occurs when all receiver and
transmitter inputs detect no signal transitions for a period of
30sec. These devices power back up, automatically,
whenever they sense a transition on any transmitter or
receiver input.
Table 1 summarizes the features of the ISL4238E/4XE, while
Application Note AN9863 summarizes the features of each
device comprising the 3V RS-232 family.
Features
• Parameters Fully Specified for 10% Tolerance Supplies
and Full Industrial Temp Range
• Available in Small QFN (5mm x 5mm) Package which is
60% Smaller than a 28 Lead TSSOP
• ESD Protection for RS-232 I/O Pins to ±15kV (IEC6100)
• DTE (ISL4244E/45E) and DCE (ISL4238E) Versions
• Lowest Supply Current in Powerdown . . . . . . . . . . . .10nA
• Active Feedback Resistors on TX and Logic Inputs
(ISL4238E)
• Flow Through Pinouts
• Manual and Enhanced Automatic Powerdown Features
• Guaranteed Minimum Data Rate
250kbps (ISL4238E/44E) / 1Mbps (ISL4245E)
• Latch-Up Free
• On-Chip Charge Pumps Require Only Four External
0.1µF Capacitors
• Wide Power Supply Range . . . . . . Single +2.7V to +5.5V
• Meets EIA/TIA-232 and V.28/V.24 Specifications at 3V
• RS-232 Compatible with VCC = 2.7V
Applications
• Any Space Constrained System Requiring RS-232 Ports
- Battery Powered, Hand-Held, and Portable Equipment
- Laptop Computers, Notebooks
- PDAs and Palmtops, Data Cables
- Cellular/Mobile Phones, Digital Cameras, GPS
Receivers
Related Literature
• Technical Brief TB363 “Guidelines for Handling and
Processing Moisture Sensitive Surface Mount Devices”
• Technical Brief TB379 “Thermal Characterization of
Packages for ICs”
• Technical Brief TB389 “PCB Land Pattern Design and
Surface Mount Guidelines for QFN Packages”
1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright © Intersil Americas Inc. 2002. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
1 page  
ISL4238E, ISL4244E, ISL4245E
Typical Operating Circuits (Continued)
ISL4244E, ISL4245E
+3.3V
C1
0.1µF
C2
0.1µF
+
0.1µF
28
+ C1+
23 C1-
29
+
C2+
30 C2-
12
T1IN
26
VCC
T1
V+
V-
11
T2IN
T2
10
T3IN
T3
27 + C3
0.1µF
31 C4
+0.1µF
6
T1OUT
7
T2OUT
8
T3OUT
RS-232
LEVELS
TTL/CMOS
LOGIC LEVELS
19
R2OUTB
18
R1OUT
1
R1IN
R1 5kΩ
17
R2OUT
2
R2IN
R2 5kΩ
15
R3OUT
14
R4OUT
R3
R4
R5OUT
13
22 R5
FORCEON
3
5kΩ
4
5kΩ
5
5kΩ
R3IN
R4IN
R5IN
RS-232
LEVELS
VCC
TO POWER
CONTROL LOGIC
21
FORCEOFF
20
INVALID GND
24
5
5 Page 
ISL4238E, ISL4244E, ISL4245E
by the internal receiver pull down resistors), the INVALID
logic detects the invalid levels and drives the output low. The
power management logic then uses this indicator to power
down the interface block. Reconnecting the cable restores
valid levels at the receiver inputs, INVALID switches high,
and the power management logic wakes up the interface
block. INVALID can also be used to indicate the DTR or
RING INDICATOR signal, as long as the other receiver
inputs are floating, or driven to GND (as in the case of a
powered down driver).
INVALID switches high 1µs after detecting a valid RS-232
level on a receiver input. INVALID operates in all modes
(forced or automatic powerdown, or forced on), so it is also
useful for systems employing manual powerdown circuitry.
2.7V
VALID RS-232 LEVEL - INVALID = 1
INDETERMINATE
0.3V
-0.3V
INVALID LEVEL - INVALID = 0
INDETERMINATE
-2.7V
VALID RS-232 LEVEL - INVALID = 1
FIGURE 6. DEFINITION OF VALID RS-232 RECEIVER LEVELS
Enhanced Automatic Powerdown
Even greater power savings is available by using these devices
which feature an enhanced automatic powerdown function.
When the enhanced powerdown logic determines that no
transitions have occurred on any of the transmitter nor receiver
inputs for 30 seconds, the charge pump and transmitters
powerdown, thereby reducing supply current to 10nA. The
ISL4238E/4XE automatically powers back up whenever it
detects a transition on one of these inputs. This automatic
powerdown feature provides additional system power savings
without changes to the existing operating system.
Enhanced automatic powerdown operates when the
FORCEON input is low, and the FORCEOFF input is high.
Tying FORCEON high disables automatic powerdown, but
manual powerdown is always available via the overriding
FORCEOFF input. Table 2 summarizes the enhanced
automatic powerdown functionality.
Figure 7 illustrates the enhanced powerdown control logic.
Note that once the ISL4238E/4XE enters powerdown
(manually or automatically), the 30 second timer remains
timed out (set), keeping the ISL4238E/4XE powered down
until FORCEON transitions high, or until a transition occurs
on a receiver or transmitter input.
The INVALID output signal switches low to indicate that
invalid levels have persisted on all of the receiver inputs for
more than 30µs (see Figure 9), but this has no direct effect
T_IN
EDGE
DETECT
R_IN
EDGE
DETECT
FORCEOFF
S
30sec
TIMER
R
AUTOPWDN
FORCEON
FIGURE 7. ENHANCED AUTOMATIC POWERDOWN LOGIC
on the state of the ISL4238E/4XE (see the next sections for
methods of utilizing INVALID to power down the device).
The time to recover from automatic powerdown mode is
typically 100µs.
Emulating Standard Automatic Powerdown
If enhanced automatic powerdown isn’t desired, the user can
implement the standard automatic powerdown feature (mimics
the function on the ISL4243E) by connecting the INVALID
output to the FORCEON and FORCEOFF inputs, as shown in
Figure 8. After 30µs of invalid receiver levels, INVALID switches
low and drives the ISL4238E/4XE into a forced powerdown
condition. INVALID switches high as soon as a receiver input
senses a valid RS-232 level, forcing the ISL4238E/4XE to
power on. See the “INVALID DRIVING FORCEON AND
FORCEOFF” section of Table 2 for an operational summary.
This operational mode is perfect for handheld devices that
communicate with another computer via a detachable cable.
Detaching the cable allows the internal receiver pull-down
resistors to pull the inputs to GND (an invalid RS-232 level),
causing the 30µs timer to time-out and drive the IC into
powerdown. Reconnecting the cablerestores valid levels,
causing the IC to power back up.
FORCEON
INVALID
FORCEOFF
ISL4238E/4XE
CPU
I/O
UART
FIGURE 8. CONNECTIONS FOR AUTOMATIC POWERDOWN
WHEN NO VALID RECEIVER SIGNALS ARE
PRESENT
Hybrid Automatic Powerdown Options
For devices which communicate only through a detachable
cable, connecting INVALID to FORCEOFF (with
FORCEON = 0) may be a desirable configuration. While the
11
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| PDF Descargar | [ Datasheet ISL4244E.PDF ] | |
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