HDMIULC6-4SC6 datasheet(6/11 Pages) STMICROELECTRONICS

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Technical information

HDMIULC6-4SC6

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Technical information

3.1

Surge protection

The HDMIULC6-4SC6 is particularly optimized to perform ESD surge protection based on

the rail to rail topology.

The clamping voltage VCL can be calculated as follows:

with: VF = VT + Rd.Ip

(VF forward drop voltage) / (VT forward drop threshold voltage)

and VTRANSIL = VBR + Rd_TRANSIL . IP

Calculation example

We assume that the value of the dynamic resistance of the clamping diode is typically:

Rd = 0.5 Ω and VT = 1.1 V.

We assume that the value of the dynamic resisteance of the transil diode is typically

Rd_TRANSIL = 0.5 Ω and VBR = 6.1 V

For an IEC 61000-4-2 surge Level 4 (Contact Discharge: Vg= 8 kV, Rg= 330 Ω),

VBUS = +5 V, and, in first approximation, we assume that: Ip = Vg / Rg = 24 A.

We find:

Note:

The calculations do not take into account phenomena due to parasitic inductances.

3.2

Surge protection application example

If we consider that the connections from the pin VBUS to VCC, from I/O to data line, and from

GND to PCB GND plane are two tracks 10 mm long and 0.5 mm wide, we can assume that

the parasitic inductances, LVBUS, LI/O, and LGND, of these tracks are about 6 nH. So when an

IEC 61000-4-2 surge occurs on the data line, due to the rise time of this spike (tr = 1 ns), the

voltage VCL has an extra value equal to LI/O.dI/dt + LGND.dI/dt.

The dI/dt is calculated as: dI/dt = Ip/tr = 24 A/ns for an IEC 61000-4-2 surge level 4 (contact

discharge Vg = 8 kV, Rg = 330 Ω

The over voltage due to the parasitic inductances is:

LI/O.dI/dt = LGND.dI/dt = 6 x 24 = 144 V

By taking into account the effect of these parasitic inductances due to unsuitable layout, the

clamping voltage will be:

We can reduce as much as possible these phenomena with simple layout optimization.

VCL+ = VTRANSIL + VF for positive surges

VCL- = - VF

for negative surges

VCL+ = +31.2 V

VCL- = -13.1 V

VCL+ = +31.2 + 144 +144 = 319.2 V

VCL- = -13.1 - 144 -144 = -301.1 V

HDMIULC6-4SC6 Datasheet(PDF) 6 Page - STMicroelectronics

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