19
Rev: C Date:2/1/06 SP526 Multi–Mode Serial Transceiver © Copyright 2006 Sipex Corporation
Phase 4
— V
DD
transfer — The fourth phase of the clock
connects the negative terminal of C
2
to ground,
and transfers the generated l0V across C
2
to C
4
,
the V
DD
storage capacitor. Again, simultaneously
with this, the positive side of capacitor C
1
is
switched to +5V and the negative side is con-
nected to ground, and the cycle begins again.
Since both V
+
and V
–
are separately generated
from V
CC
; in a no–load condition V
+
and V
–
will
be symmetrical. Older charge pump approaches
that generate V
–
from V
+
will show a decrease in
the magnitude of V
–
compared to V
+
due to the
inherent inefficiencies in the design.
The clock rate for the charge pump typically
operates at 15kHz. The external capacitors can
be as low as 1.0µF with a 16V breakdown
voltage rating.
ESD Tolerance
The SP526 device incorporates ruggedized
ESD cells on all driver output and receiver input
pins. The ESD structure is improved over our
previous family for more rugged applications
and environments sensitive to electro-static
discharges and associated transients. The
improved ESD tolerance is at least ±15kV
without damage nor latch-up.
There are different methods of ESD testing
applied:
a) MIL-STD-883, Method 3015.7
b) IEC1000-4-2 Air-Discharge
c) IEC1000-4-2 Direct Contact
The Human Body Model has been the generally
accepted ESD testing method for semiconductors.
This method is also specified in MIL-STD-883,
Method 3015.7 for ESD testing. The premise of
this ESD test is to simulate the human body’s
potential to store electro-static energy and
discharge it to an integrated circuit. The
simulation is performed by using a test model as
shown in Figure 35. This method will test the
IC’s capability to withstand an ESD transient
during normal handling such as in manufacturing
areas where the ICs tend to be handled frequently.
The IEC-1000-4-2, formerly IEC801-2, is
generally used for testing ESD on equipment and
systems. For system manufacturers, they must
guarantee a certain amount of ESD protection
since the system itself is exposed to the outside
environment and human presence. The premise
with IEC1000-4-2 is that the system is required
to withstand an amount of static electricity when
ESD is applied to points and surfaces of the
equipment that are accessible to personnel during
normal usage. The transceiver IC receives most
R
C
SW
DC Power
Source
C
S
R
S
SW2
Device
Under
Test
Figure 35. ESD Test Circuit for Human Body Model
