5
Detailed Description
The ICL32X7 interface ICs operate from a single +3V to
+5.5V power supply, guarantee a 250kbps minimum data
rate, require only four small external 0.1F capacitors,
feature low power consumption, and meet 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 ICL32XX family utilizes regulated on-chip dual
charge pumps as voltage doublers, and voltage inverters to
generate 5.5V transmitter supplies from a V
CC
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 0.1F capacitors for the
voltage doubler and inverter functions at V
CC
= 3.3V. See
the “Capacitor Selection” section, and Table 3 for capacitor
recommendations for other operating conditions. 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.
ICL3217 transmitter outputs disable and assume a high
impedance state when the device enters the automatic
powerdown mode. These outputs may be driven to 12V
when disabled.
Both 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 V
CC
3.3V, R
L
=3k, and C
L
= 250pF, one
transmitter easily operates at 800kbps.
Transmitter inputs float if left unconnected, and may cause
I
CC
increases. Connect unused inputs to GND for the best
performance.
Input Hysteresis 25 - 0.3 - V
Input Resistance 25357k
TRANSMITTER OUTPUTS
Output Voltage Swing All Transmitter Outputs Loaded with 3k to Ground Full 5.0 5.4 - V
Output Resistance V
CC
= V+ = V- = 0V, Transmitter Output = 2V Full 300 10M -
Output Short-Circuit Current Full - 35 60 mA
Output Leakage Current
(ICL3217 Only)
V
OUT
= 12V, V
CC
= 0V or 3V to 5.5V
In Automatic Powerdown
Full - - 25 A
TIMING CHARACTERISTICS
Maximum Data Rate
(One Transmitter Switching)
V
CC
= 3.15V, C
1
- C
4
= 0.1F, R
L
= 3kC
L
= 1000pF Full 250 500 - kbps
V
CC
= 3.0V, C
1
- C
4
= 0.22F, R
L
= 3kC
L
= 1000pF Full 250 286 - kbps
V
CC
4.5V, C
1
- C
4
= 0.1F, R
L
= 3kC
L
= 1000pF Full 250 310 - kbps
Receiver Propagation Delay Receiver Input to Receiver
Output, C
L
= 150pF
t
PHL
25 - 0.3 - s
t
PLH
25 - 0.3 - s
Transmitter Skew t
PHL
- t
PLH
Full - 200 1000 ns
Receiver Skew t
PHL
- t
PLH
Full - 100 500 ns
Transition Region Slew Rate V
CC
= 3.3V, R
L
=3kto 7k
Measured From +3V to -3V or -3V
to +3V
C
L
= 200pF to 2500pF 25 4 15 30 V/s
C
L
= 200pF to 1000pF 25 6 15 30 V/s
ESD PERFORMANCE
RS-232 Pins (T
OUT
, R
IN
) Human Body Model 25 - 15 - kV
IEC61000-4-2 Contact Discharge 25 - 8-kV
IEC61000-4-2 Air Gap Discharge 25 - 6-kV
All Other Pins Human Body Model 25 - 2-kV
Electrical Specifications Test Conditions: V
CC
= 3V to 5.5V, C
1
- C
4
= 0.1F; Unless Otherwise Specified.
Typicals are at T
A
= 25°C (Continued)
PARAMETER TEST CONDITIONS
TEMP
(°C) MIN TYP MAX UNITS
ICL3207, ICL3217