MIL-PRF-19500/477K
6.5 Applications data.
6.5.1 Half-sine-wave application with 1N5807(US), 1N5809(US), 1N5811(US). For a printed board mounting
example with FR4 base material where the full 3 amp IO rating (half-sine-wave) is used at a TJ of 175ēC and ambient
temperature of 55ēC, the following steps guide the user in what the printed board copper mounting pad size will need
to be with 1 ounce, 2 ounce, and 3 ounce copper for 1N5807(US), 1N5809(US), and 1N5811(US). For axial-leaded,
the lead length for mounting will be .187 inch (4.76 mm) or less from body to entry point on PCB surface. See 6.5.3
for the smaller example devices 1N5802 to 1N5806 or 1N5802(US) to 1N5806US.
a. Use the IO versus Po curve on figure 10 to look up 3 amps (X-axis) and follow up to the TJ =175ēC curve
(lower) for 2.30 watts.
b. Calculate maximum thermal resistance needed (175ēC 55ēC) / 2.30 W = 52ēC/W.
c. Look up thermal resistance of 52ēC/W on Y-axis using a thermal resistance versus copper mounting pad area
plot on one of the three curves on figure 11 for different weights of copper foil and then intersect curve
horizontally to get the answer. These curves assume still air and horizontal printed board position.
d. In this example, the copper mounting pad sizes for the different copper foil weights would be as follows:
2
2
1) .50 in (1.27 mm ) for 1 ounce copper foil.
2
2
2) .30 in (0.76 mm ) for 2 ounce copper foil.
2
2
3) .20 in (0.51 mm ) for 3 ounce copper foil.
e. Add a conservative guard-band to the copper mounting pad size (larger) to keep TJ below 175ēC.
6.5.2 Square-wave application with 1N5807(US), 1N5809(US), 1N5811(US). For a printed board mounting
example with FR4 base material to support a 1 amp IO square wave switching at a 0.50 duty factor (50 percent duty
cycle) at TJ=125ēC and ambient temperature of 55ēC, the following steps guide the user in what the printed board
copper mounting pad size will need to be with 1 ounce, 2 ounce, and 3 ounce copper.
a. Find size of copper mounting pads on standard FR4 base material to support operation at 1 amp IO square
wave switching at a 0.50 duty factor (50 percent duty cycle) at TJ=125ēC with TA = 55ēC.
b. Calculate peak IF = 1 A / 0.50 duty factor = 2 amps.
c. Use the VF versus IF curve on figure 12 to look up IF = 2 A (Y-axis) and follow across to the TJ = 125ēC curve
(middle) for VF = 0.65 V.
d. Calculate power = IF * VF * duty factor = 2 * 0.65 * 0.50 = 0.65 W.
e. Calculate maximum thermal resistance needed (125ēC 55ēC) / 0.65 W = 107ēC/W.
f. Look up thermal resistance of 107ēC/W on the Y-axis using a thermal resistance versus copper mounting pad
area plot on one of the three curves on figure 11 for different weights of copper foil cladding and then intersect
curve horizontally to get the answer. Curves assume still air and horizontal printed board position.
g. In this example, the copper mounting pad sizes for the different copper foil weights would be as follows:
2
2
1) .058 in (1.4732 mm ) for 1 ounce copper foil.
2
2
2) .038 in (0.9652 mm ) for 2 ounce copper foil.
2
2
3) .024 in (0.6096 mm ) for 3 ounce copper foil.
h. A conservative pad guard-band is optional since TJ is only 125ēC. NOTE: Multilayer printed boards or forced
air cooling will improve performance. Closed confinement of the printed boards or will do the opposite. Use
sound thermal management.
6.5.3 Half-sine-wave application with 1N5802(US), 1N5804(US), 1N5806(US). For a printed board mounting
example with FR4 base material where the full 1 amp IO rating (half-sine-wave) is used at a TJ of 175ēC and ambient
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