4
FN6017.3
March 15, 2005
Detailed Description
The ISL83384E operates from a single +3V to +5.5V supply,
guarantees a 250Kbps minimum data rate, requires only four
small external 0.1
F capacitors, features low power
consumption, and meets all ElA RS-232C and V.28
specifications. The circuit is divided into three sections: The
charge pump, the transmitters, and the receivers.
Charge-Pump
Intersil’s new ISL83384E utilizes regulated on-chip dual
charge pumps as voltage doublers, and voltage inverters to
generate
±5.5V transmitter supplies from a VCC supply as
low as 3.0V. This allows these devices to maintain RS-232
compliant output levels over the
±10% tolerance range of
3.3V powered systems. The efficient on-chip power supplies
require only four small, external 0.1
F capacitors for the
voltage doubler and inverter functions over the full VCC
range. The charge pumps operate discontinuously (i.e., they
turn off as soon as the V+ and V- supplies are pumped up to
the nominal values), resulting in significant power savings.
Transmitters
The transmitters are proprietary, low dropout, inverting
drivers that translate TTL/CMOS inputs to EIA/TIA-232
output levels. Coupled with the on-chip
±5.5V supplies, these
transmitters deliver true RS-232 levels over a wide range of
single supply system voltages.
All transmitter outputs disable and assume a high
impedance state when the device enters the powerdown
mode (see Table 2). These outputs may be driven to
±12V
when disabled.
All devices guarantee a 250Kbps data rate for full load
conditions (3k
and 1000pF), V
CC ≥ 3.0V, with one
transmitter operating at full speed. Under more typical
conditions of VCC ≥ 3.3V, RL = 3k, and CL = 250pF, one
transmitter easily operates at 900Kbps.
Transmitter inputs float if left unconnected (there are no pull-
up resistors), and may cause ICC increases. Connect
unused inputs to GND for the best performance.
Receivers
The ISL83384E contains standard inverting receivers that
three-state via the SHDN control line. Receivers driving
powered down peripherals must be disabled to prevent
current flow through the peripheral’s protection diodes (see
Figures 2 and 3).
Transmitter Propagation Delay
Transmitter Input to
Transmitter Output,
CL = 1000pF
tPHL
Full
-
0.6
3.5
s
tPLH
Full
-
0.7
3.5
s
Receiver Propagation Delay
Receiver Input to Receiver
Output, CL = 150pF
tPHL
Full
-
0.2
1
s
tPLH
Full
-
0.3
1
s
Transmitter Output Enable Time
From SHDN Rising Edge to TOUT = ±3V
25
-
50
-
s
Transmitter Output Disable Time
From SHDN Falling Edge to TOUT = ±5V
25
-
600
-
ns
Transmitter Skew
tPHL - tPLH (Note 3)
25
-
100
-
ns
Receiver Skew
tPHL - tPLH
25
-
100
-
ns
Transition Region Slew Rate
RL = 3k to 7k,
Measured From 3V to -3V or
-3V to 3V
VCC = 3.3V, CL = 150pF to
2500pF
25
4
-
V/
s
VCC = 4.5V, CL = 150pF to
2500pF
25
6
-
V/
s
ESD PERFORMANCE
RS-232 Pins (TOUT, RIN)
Human Body Model
25
-
±15
-
kV
IEC61000-4-2 Contact Discharge
25
-
±8-
kV
IEC61000-4-2 Air Gap Discharge
25
-
±15
-
kV
All Other Pins
Human Body Model
25
-
±3-
kV
NOTE:
3. Transmitter skew is measured at the transmitter zero crossing points.
Electrical Specifications
Test Conditions: VCC = 3V to 5.5V, C1 - C4 = 0.1F; Unless Otherwise Specified.
Typicals are at TA = 25°C (Continued)
PARAMETER
TEST CONDITIONS
TEMP
(°C)
MIN
TYP
MAX
UNITS
TABLE 2. POWERDOWN AND ENABLE LOGIC TRUTH TABLE
SHDN
INPUT
TRANSMITTER
OUTPUTS
RECEIVER
OUTPUTS
MODE OF OPERATION
H
Active
Normal Operation
L
High-Z
Manual Powerdown
ISL83384E