AN2434 Freescale Semiconductor / Motorola, AN2434 Datasheet - Page 23

• Manufacturer Part Number: AN2434
• Description: Input/Output (I/O) Pin Drivers
• Manufacturer: Freescale Semiconductor / Motorola

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Electrostatic Discharge (ESD) in Integrated Circuits - A Primer
The Machine Model (MM) is very similar to HBM, but instead of a simulated human body, a
simulated machine contacts the grounded device. Since there is metal-to-metal contact, the
discharge resistor is replaced by a short circuit.
oscillation in the waveform (ringing).
A 400V MM stress will impart a peak current of 7.0A to the device.
The Charged Device Model (CDM) is very different from both HBM and MM.
device itself is charged up, and discharges to ground. For instance, a device sliding out of a
plastic rail will charge up via triboelectric charging if the rail isn't treated with an anti-static
coating. An IC has much less capacitance than a human body, typically only a few pF, and only a
small amount of charge is needed to increase the potential on a device to several hundred v o l t s
(V=Q/C).
capacitance, as is shown in Figure 2.
+
+
+
+
+ +
+
+
+
+
+
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Any charge built up on the device discharges very quickly because of this small
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ZAP!
C
u
r
r
e
n
t
0
Figure 1 - Human Body Model (HBM) stressing.
with a 2000V HBM event
Peak current is 1.33A
100
GROUND
Time (nanoseconds)
Total duration is about the same as with an HBM event.
200
Voltage
300
Supply
High
With no series resistance, there is more
HBM Equivalent Circuit
Charging
Resistor
100MΩ
400
500
SW
100pF
Storage
Capacitor
GROUND
Discharge
Resistor
600
1.5KΩ
(rev 2.0 - 5/5/95)
In this case, the
Device Under Test
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