AD ADM101E

a
Craft PortTM Tiny RS-232 Transceiver for
Portable Applications
ADM101E
FEATURES
460 kbit/s Transmission Rate
Single +5 V Power Supply
Compatible with RS-232 Input/Output Levels
0.1 ␮F Charge Pump Capacitors
One Driver and One Receiver
On-Board DC-DC Converter
ⴞ4.2 V Output Swing with +5 V Supply
Low Power BiCMOS: 500 ␮A ICC
Ultralow Power (1 ␮A) Shutdown Mode
10-Lead ␮SOIC Package
APPLICATIONS
Mobile Telephones
Palmtop Computers
PDAs
Portable Instrumentation
GPS Receivers
GENERAL DESCRIPTION
The ADM101E is a single channel RS-232 driver and receiver in
the Analog Devices Craft Port series, designed to operate from a
single, +5 V supply. A highly efficient charge-pump voltage
inverter generates an on-chip –5 V supply, which eliminates the
need for a negative power supply for the driver and permits
RS-232 compatible output levels to be developed using charge
pump capacitors as small as 0.1 µF.
A shutdown input disables the charge pump and puts the device
into a low power shutdown mode, in which the current consumption is typically less than 1 µA. The transmitter is disabled
during shutdown but the receiver remains functional.
FUNCTIONAL BLOCK DIAGRAM
0.1mF
+
0.1mF
+
GND
C1–
0.1mF
+
V–
2
+5V TO –5V
VOLTAGE
INVERTER
3
ADM101E
1
TIN 4
ROUT 5
10
9
VCC
+5V
C1+
8 SD
7 TOUT
T1
R1
6 RIN
An epitaxial BiCMOS construction minimizes power consumption to 3 mW and also guards against latch-up. Overvoltage
protection is provided allowing the receiver inputs to withstand
continuous voltages in excess of ± 30 V. In addition, all I-O pins
have ESD protection to levels greater than 15 kV.
The ADM101E is available in a 10-lead µSOIC package, which
makes it ideal for serial communications in small, portable applications such as palmtop computers and mobile telephones,
where a full, RS-232 serial interface is not required, but compact size and low power drain are paramount.
Craft Port is a trademark of Analog Devices, Inc.
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1999
(VCC = +5 V ⴞ 10%, C1 = C2 = 0.1 ␮F. All specifications TMIN to TMAX unless
ADM101E–SPECIFICATIONS otherwise noted.)
Parameter
Min
Typ
Output Voltage Swing
± 3.5
± 3.25
± 4.2
± 4.2
VCC Power Supply Current (Unloaded)
VCC Power Supply Current (Loaded)
VCC Power Supply Current (Shutdown)
Input Logic Threshold Low, VINL
Input Logic Threshold High, VINH
Input Leakage Current
RS-232 Input Voltage Range
RS-232 Input Threshold Low
RS-232 Input Threshold High
RS-232 Input Hysteresis
RS-232 Input Resistance
TTL/CMOS Output Voltage Low, VOL
TTL/CMOS Output Voltage High, VOH
Propagation Delay
Instantaneous Slew Rate1
Transition Region Slew Rate
Baud Rate
Output Resistance
RS-232 Output Short Circuit Current
0.5
1.85
3
1
2.5
1
0.8
Test Conditions/Comments
V
V
VCC = 5 V ± 5%, TOUT Loaded with 3 kΩ to GND
VCC = 5 V ± 10%, TOUT Loaded with 3 kΩ to
GND
No Load, TIN = VCC or GND
TOUT Loaded with 3 kΩ to GND
SD Input = VCC
0.25
25
11
± 25
kB
Ω
mA
±1
+15
2.2
2.4
0.2
5
2.6
7
0.4
3.5
460
300
Units
mA
mA
µA
V
V
µA
V
V
V
V
kΩ
V
V
µs
V/µs
V/µs
2.4
–15
0.8
Max
± 60
IOUT = 1.6 mA
IOUT = –1.0 mA
RS-232 to TTL
CL = 10 pF, RL = 3 kΩ–7 kΩ, TA = +25°C
RL = 3 kΩ, CL = 1000 pF
Measured from +3 V to –3 V or Vice Versa
RL = 3 kΩ, CL = 1 nF
VCC = 0 V, VOUT = ± 2 V
NOTES
1
Sample tested to ensure compliance.
Specifications subject to change without notice.
ABSOLUTE MAXIMUM RATINGS*
ORDERING GUIDE
(TA = +25°C unless otherwise noted)
VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +6 V
V– . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +0.3 V to –6 V
Input Voltages
Driver Input TIN . . . . . . . . . . . . . . –0.3 V to (VCC, +0.3 V)
Receiver Input RIN . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 30 V
Output Voltages
Driver Output TOUT . . . . . . . . (VCC, +0.3 V) to (V–, –0.3 V)
Receiver Output ROUT . . . . . . . . . . . –0.3 V to (VCC +0.3 V)
Short Circuit Duration
TOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Continuous
Power Dissipation
RM-10 (Derate 12 mW/°C Above +70°C) . . . . . . . 1488 mW
Thermal Impedance . . . . . . . . . . . . . . . . . . . . . . . +135°C/W
Operating Temperature Range
Industrial (A Version) . . . . . . . . . . . . . . . . –40°C to +85°C
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Lead Temperature Soldering
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . . +215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . . +220°C
ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . >2000 V
ESD Rating (I-O Pins) . . . . . . . . . . . . . . . . . . . . . . . . . 15 kV
Model
Temperature
Range
Package
Description
Package
Option
ADM101EARM
–40°C to +85°C
µSOIC
RM-10
*This is a stress rating only; functional operation of the device at these or any other
conditions above those indicated in the operation sections of this specification is
not implied. Exposure to absolute maximum rating conditions for extended
periods of time may affect reliability.
–2–
REV. 0
ADM101E
PIN FUNCTION DESCRIPTION
PIN CONFIGURATION
Pin
No.
Mnemonic
Function
1
2
GND
C1–
Ground Pin. Must be connected to 0 V.
Negative Terminal of C1 (if C1 is Polarized
Capacitor).
Internally Generated Negative Supply Voltage.
Driver Input (3 V to 5 V TTL/CMOS
Logic Levels).
Receiver Output (3 V to 5 V TTL/CMOS
Logic Levels).
Receiver Input (EIA-232 Signal Levels).
Driver Output (EIA-232 Signal Levels).
Shutdown Input. Logic 1 on this input puts
the ADM101E into low power shutdown mode.
Positive Terminal of Charge Pump Capacitor
(if C1 is Polarized Capacitor).
Positive Power Supply, Nominally +5 V.
3
4
V–
TIN
5
ROUT
6
7
8
RIN
TOUT
SD
9
C1+
10
VCC
GND 1
C1–
2
V–
3
TIN 4
ROUT
5
10 VCC
ADM101E
TOP VIEW
(Not to Scale)
9
C1+
8
SD
7
TOUT
6 RIN
Typical Performance Characteristics
14
12
–1
10
–2
IDD – mA
CHARGE PUMP VOLTAGE – Volts
0
–3
6
–4
4
–5
–6
2
0
5
10
15
CURRENT – mA
20
0
25
0
500
1000
1500
2000
2500
LOAD CAPACITANCE – pF
3000
3500
Figure 2. IDD vs. Load Capacitance @ 460 kbps
Figure 1. Charge Pump Voltage vs. Current
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8
–3–
ADM101E
6
40
TX HI
5
30
4
SERIES 1
SLEW RATE – Volts/ms
3
TXO/P – Volts
2
1
0
–1
–2
20
10
0
–10
–20
SERIES 2
–3
TX LO
–30
–4
–5
–40
0
500
1000
1500
LOAD CAPACITANCE – pF
2000
2500
0
Figure 3. Transmitter Output Voltage vs. Load Capacitance
@ 460 kbps
200
300
400
DATA RATE – kbps
500
600
Figure 5. Slew Rate vs. Data Rate
6
5
TX HI
4
TX HI
4
TX OUTPUT VOLTAGE
3
2
TXO/P HI & LO
100
0
–2
2
1
0
–1
–2
TX LO
–3
–4
TX LO
–4
–6
0
1
2
3
4
VCC – Volts
5
6
–5
7
Figure 4. Tx Output Voltage vs. Supply
0
2
4
6
8
10
LOAD CURRENT – mA
12
14
Figure 6. Transmitter Output Voltage vs. Load Current
–4–
REV. 0
ADM101E
GENERAL DESCRIPTION
Charge Pump Capacitors And Supply Decoupling
The ADM101E is an RS-232 compatible line driver/receiver in
the Analog Devices Craft Port series, containing one driver (transmitter) and one receiver. It is ideal for serial communication in
small portable devices such as mobile telephones, palmtop personal computers and personal digital assistants, where a full,
RS-232 serial interface is not required, and only Tx and Rx lines
are required for low speed communication between devices. The
ADM101E operates from a single, +5 V supply, and generates
its own, on-chip, –5 V power supply, thus removing the need for
a negative power supply for the driver.
For proper operation of the charge pump, the capacitors should
have an equivalent series resistance (ESR) less than 1 Ω. As the
charge pump draws current pulses from VCC, the VCC decoupling capacitor should also have low ESR. The VCC decoupling
capacitor and V– reservoir capacitor should also have low ESR
because they determine how effectively ESD pulses are clamped
to VCC or V– by the on-chip clamp diodes. Tantalum or monolithic ceramic capacitors are suitable for these components. If
using tantalum capacitors, do not forget to observe polarity.
Transmitter (Driver) Section
The driver converts 5 V logic input levels into RS-232 compatible output levels. With VCC = +5 V and driving an EIA-232
load, the output voltage swing is typically ± 4.2 V.
CIRCUIT DESCRIPTION
The internal circuitry consists of three main sections. These are:
1. A charge pump dc-to-dc converter.
2. 5 V logic to EIA-232 driver.
3. EIA-232 to 5 V logic receiver.
Receiver Section
The receivers are inverting level-shifters that accept EIA-232
input levels and translate them into 5 V logic output levels.
The inputs have internal 5 kΩ pull-down resistors to ground and
are also protected against overvoltages of up to ± 25 V. The
guaranteed switching thresholds are 0.8 V minimum and 2.8 V
maximum. An unconnected receiver input is pulled to 0 V by
the internal 5 kΩ pull-down resistor. This, therefore, results in a
Logic 1 output level for unconnected inputs or for inputs connected to GND.
Charge Pump DC-DC Converter
The dc-dc converter generates a negative supply voltage from
the +5 V supply, thus removing the need for a separate –5 V
rail. It consists of an on-chip 200 kHz oscillator, switching matrix and two external capacitors, as shown in Figure 7.
S1
VCC
S2
GND
S3
+
C1
+
S4
GND
The receivers have Schmitt trigger input with a hysteresis level
of 0.25 V. This ensures error-free reception for both noisy inputs and for inputs with slow transition times.
C2
V– = –VCC
INTERNAL
OSCILLATOR
SHUTDOWN INPUT
The shutdown input allows the ADM101E to be put into an
ultralow power mode where the dc-dc converter is switched off
and the transmitter is disabled. The receiver remains active
during shutdown. Logic 0 at this input enables the ADM101E,
while a Logic 1 at this input shuts down the ADM101E.
Figure 7. Charge Pump DC–DC Converter
When S1 and S2 are closed, S3 and S4 are open, and C1
charges to +VCC. S1 and S2 are then opened, while S3 and S4
are closed to connect C1 across C2, dumping charge into C2.
Since the positive terminal of C2 is at ground, a negative voltage
will be built up on its negative terminal with each cycle of the
oscillator. This voltage depends on the current drawn from C2.
If the current is small, the voltage will be close to –VCC, but will
fall as the current drawn increases.
REV. 0
–5–
ADM101E
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
10-Lead ␮SOIC
(RM-10)
10
C3444–2–3/99
0.124 (3.15)
0.112 (2.84)
6
0.124 (3.15)
0.112 (2.84)
0.199 (5.05)
0.187 (4.75)
1
5
PIN 1
0.0197 (0.50) BSC
0.038 (0.97)
0.030 (0.76)
0.122 (3.10)
0.110 (2.79)
0.120 (3.05)
0.112 (2.84)
0.043 (1.09)
0.037 (0.94)
0.022 (0.56)
0.021 (0.53)
PRINTED IN U.S.A.
68
0.006 (0.15) 0.016 (0.41) SEATING
08
PLANE 0.011 (0.28)
0.002 (0.05) 0.006 (0.15)
0.003 (0.08)
–6–
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