HDSP-5323 Agilent(Hewlett-Packard), HDSP-5323 Datasheet - Page 5

• Manufacturer Part Number: HDSP-5323
• Description: 14.2 mm (0.56 inch) Seven Segment Displays
• Manufacturer: Agilent(Hewlett-Packard)

The I
datasheet.
In the case the supply cables of the +12V and +5V are reversed, the +5V (PL5) internal protection of the
HDP01-512N immediately shorts circuits +5V rail and ensures on efficient protection of the electronic mod-
ule.
ABOUT THE +12V PROTECTION
The +12V internal protection (PL12 termination) eliminates all transients appearing on the +12V supply rail.
In normal conditions (region 4 of figure A.3) its leakage current is 1 A maximum at 12V @ 25°C. When a
surge occurs on the +12V rail, the overvoltage is clamped (region 5) and the electronic module connected
to this rail is protected.
Fig. A.3: Current and voltage characteristic of the
+12V protection.
To evaluate the clamping voltage appearing on the +12V rail when a transient occurs, the next formula is
needed :
Vcl = V
I
I
If, for example, we consider a 50V combined surge 1.2/50 s - 8/20 s, as defined by the standard
IEC1000-4-5, the Vcl is calculated as:
Vcl = 16 + 2.5*I
then it comes up with Vcl = 17.9V and I
The impact of the temperature on the clamping voltage can be considered as to be :
Vcl(T°C) = Vcl(25°C) * (1 + T(T°C-25°C)) where T°C is the ambient temperature for which the module shall
run.
The HDP01-0512N +12V protection has a power dissipation capability that is given in the figure 2 of this
datasheet named "Peak pulse power versus exponential pulse duration". This figure is necessary to deter-
mine if the power involved in the +12V protection does not exceed the maximum power the HDP01 +12V
protection can support. For example, considering the last calculation where Vcl=17.9 and I
peak power is in that case 12.5W (Vcl*I
to the curve of figure 2, then we see the dissipated power is much lower than the +12V protection limit
(200W @ 20 s) this tells us the +12V protection of the HDP01-0512N can easily withstand such a 12.5W
surge.
PP
PP
is the peak current given by the transient which is :
= (Vtransient - Vcl)/Rs
I
TSM
BR
value as a function of the pulse duration tp for the HDP01 device is given on the figure 1 of this
max + Rd*I
PP
and I
PP
4
PP
= (50 - Vcl) / 42
V
CL
PP
PP
5
with a typical Rd equals to 2.5
) for a 20 s exponential surge duration. If we compare this value
= 0.7A
Vtransient = peak voltage of the transient
Rs is the series resistance of the surge generator.
R
V
S
= 42
The clamping voltage (Vcl) is depending on several
parameters which are :
- current induced by the transient (Ipp)
- ambient temperature effect ( T)
- breakdown voltage of the protection (V
- dynamic resistance of the protection (Rd)
(generator impedance)
HDP01-0512N
PP
BR
=0.7A, the
)
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