CM1231 Datasheet, PDF (9/11 Pages) California Micro Devices Corp – Two-Channel PicoGuard XPTM ESD Clamp Protection Array

Issue X-1
CM1231
CM1231 Application and Guidelines
The CM1231 has an integrated zener diode between
V_P and V_N (for each of the two stages). This greatly
reduces the effect of supply rail inductance L₂ on V_CL
by clamping V_P at the breakdown voltage of the zener
diode. However, for the lowest possible V_CL, especially
when V_P is biased at a voltage significantly below the
zener breakdown voltage, it is recommended that a
0.22μF ceramic chip capacitor be connected between
V_P and the ground plane. With the CM1231, this
additional bypass capacitor is generally not required.
As a general rule, the ESD Protection Array should be
located as close as possible to the point of entry of
expected electrostatic discharges. The power supply
bypass capacitor mentioned above should be as close
to the V_P pin of the Protection Array as possible, with
minimum PCB trace lengths to the power supply,
ground planes and between the signal input and the
ESD device to minimize stray series inductance.
Figure 14. Typical Layout with Optional V_P Cap
Footprint
Additional Information
See also California Micro Devices Application Note AP-209, “Design Considerations for ESD Protection,” in the
Applications section at www.calmicro.com.
© 2007 California Micro Devices Corp. All rights reserved.
12/17/07
490 N. McCarthy Blvd., Milpitas, CA 95035-5112 ● Tel: [phone] ● Fax: [phone] ● www.cmd.com 9