Transmitter Output High Voltage vs. Load Capacitance
Transmitter Slew Rate vs. Load Capacitance
The recommended capacitors are 0.1µF. However, larger
capacitors for the charge pump may be used to minimized
ripples on V+ and V− pins.
POWER SUPPLY DECOUPLING
In some applications that are sensitive to power supply noise
from the charge pump, place a decoupling capacitor, Cbp,
from VS to GND. Use at least a 0.1µF capacitor or the same
size as the charge pump capacitors (C1 − C4).
The dual internal charged-pump provides the ±10V to the to
transmitters. Using capacitor C1, the charge pump converts
+5V to +10V then stores the +10V in capacitor C3. The
charge pump uses capacitor C2 to invert the +10V to −10V.
The −10V is then stored in capacitor C4.
ELECTROSTATIC DISCHARGE PROTECTION
ESD protection has been placed at all pins to protect the
device from ESD. All pins except for the transmitter output
pins (pins 7 and 14) and receiver input pins (pins 8 and 13)
have a ESD rating of 2kV Human Body Model (HBM) and
200V Machine Model (MM). The RS-232 bus pins (pins 7, 8,
13 and 14) have a more robust ESD protection. The RS-232
bus pins have a ESD rating of 15kV HBM and IEC 1000-4-2,
air-gap. In addition the bus pins meet an ESD rating of 8kV
with IEC 1000-4-2, contact. The ESD structures can with-
stand a high ESD event under the following conditions:
powered-on, powered-off, and Input connected to high and
low with outputs unloaded.
HUMAN BODY MODEL
The Human Body Model is an ESD testing standard, defined
in Mil-STD-883C method 3015.7. It simulates a human dis-
charging an ESD charge to the IC device. The rise time is
approximately 10 ns and decay time is approximately 150
ns. The waveform is obtained by discharging 2kV volts ca-
pacitor through a resistor, R2 = 1.5 kΩ. The peak current is
FIGURE 1. HBM ESD Test Model
FIGURE 2. HBM Waveform