DATASHEET
ISL4238E, ISL4244E, ISL4245E
QFN Packaged, ±15kV ESD Protected, +2.7V to +5.5V, 10Nanoamp, 250kbps/
1Mbps, RS-232 Transceivers with Enhanced Automatic Power-down
The Intersil ISL4238E, ISL4244E and ISL4245E 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
V
CC
= 3.0V. Additionally, they provide ±15kV ESD protection
(IEC61000-4-2 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 power-down functions, reduce the standby supply
current to a
10nA
trickle. Tiny 5mmx5mm
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/ISL4244E)/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 32 Ld 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 power-down
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 30s. 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,
ISL4244E, ISL4245, while Application Note AN9863
summarizes the features of each device comprising the 3V
RS-232 family.
FN8038
Rev 5.00
May 13, 2010
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 (IEC61000)
• DTE (ISL4244E/45E) and DCE (ISL4238E) Versions
• Lowest Supply Current in Power-down . . . . . . . . . . .10nA
• Active Feedback Resistors on T
X
and Logic Inputs
(ISL4238E)
• Flow Through Pinouts
• Manual and Enhanced Automatic Power-down Features
• Guaranteed Minimum Data Rate
250kbps (ISL4238E/ISL4244E) / 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 V
CC
= 2.7V
• Pb-Free Available (RoHS Compliant)
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”
FN8038 Rev 5.00
May 13, 2010
Page 1 of 17
ISL4238E, ISL4244E, ISL4245E
Pinouts
ISL4238E
(32 LD QFN)
TOP VIEW
GND
V
CC
C2+
C1+
C2-
NC
NC
V+
V-
V-
ISL4244E, ISL4245E
(32 LD QFN)
TOP VIEW
V
CC
26
C2+
C1+
C2-
NC
25
24
GND
23
C1-
22
FORCEON
21
FORCEOFF
PD
20
INVALID
19
R2
OUTB
18
R1
OUT
17
R2
OUT
9
NC
10
T3
IN
11
T2
IN
12
T1
IN
13
R5
OUT
14
R4
OUT
15
R3
OUT
16
NC
V+
27
32
T1
OUT
T2
OUT
T3
OUT
R1
IN
R2
IN
T4
OUT
R3
IN
T5
OUT
1
2
3
4
5
6
7
8
9
NC
31
30
29
28
27
26
25
24
C1-
23
T1
IN
22
T2
IN
21
T3
IN
R1
IN
R2
IN
R3
IN
R4
IN
R5
IN
T1
OUT
T2
OUT
T3
OUT
1
2
3
4
5
6
7
8
32
31
30
29
28
PD
20
R1
OUT
19
R2
OUT
18
T4
IN
17
R3
OUT
10
FORCEON
11
FORCEOFF
12
INVALID
13
NC
14
R1
OUTB
15
T5
IN
16
NC
Pin Descriptions
PIN
V
CC
V+
V-
GND
C1+
C1-
C2+
C2-
T
IN
T
OUT
R
IN
R
OUT
R
OUTB
INVALID
System power supply input (2.7V to 5.5V).
Internally generated positive transmitter supply (+5.5V).
Internally generated negative transmitter supply (-5.5V).
Ground connection. This is also the potential of the thermal pad (PD).
External capacitor (voltage doubler) is connected to this lead.
External capacitor (voltage doubler) is connected to this lead.
External capacitor (voltage inverter) is connected to this lead.
External capacitor (voltage inverter) is connected to this lead.
TTL/CMOS compatible transmitter Inputs. (Note)
±15kV ESD Protected
,
RS-232 level (nominally ±5.5V) transmitter outputs.
±15kV ESD Protected
,
RS-232 compatible receiver inputs.
TTL/CMOS level receiver outputs.
TTL/CMOS level, noninverting, always enabled receiver outputs.
Active low output that indicates if no valid RS-232 levels are present on any receiver input.
FUNCTION
FORCEOFF Active low to shut down transmitters and on-chip power supply. This overrides any automatic circuitry and FORCEON (see Table 2).
FORCEON
NC
PD
Active high input to override automatic power-down circuitry thereby keeping transmitters active. (FORCEOFF must be high).
No Connection
Exposed Thermal Pad. Connect to GND.
NOTE: ISL4238E input pins incorporate positive feedback resistors. Once the input is driven to a valid logic level, the feedback resistor maintains
that logic level until V
CC
is removed. Unused transmitter inputs may be left unconnected by the user.
FN8038 Rev 5.00
May 13, 2010
Page 3 of 17
Analog electronics
京公网安备 11010802033920号
EEWORLD
