3
Rectifier Device Data
Figure 5. Steady–State Thermal Resistance Figure 6. Typical Capacitance
3/40
L, LEAD LENGTH (INCHES)
90
80
60
70
50
VR, REVERSE VOLTAGE (VOL TS)
50 800
60
40
30
20
RJL, THERMAL RESISTANCE,
40
30
20
3/81/8 1/4 1/2 5/8 7/8 1.0 60 7010 20 30 40
50
70
80
10
100
200
C, CAPACITANCE (pF)
q
JUNCTION–T O–LEAD ( C/W)
°
BOTH LEADS TO HEAT SINK,
EQUAL LENGTH
MAXIMUM
TYPICAL
10090
TJ = 25
°
C
f = 1 MHz
NOTE 3 — MOUNTING DATA:
Data shown for thermal resistance junction–to–ambient
(RθJA) for the mounting shown is to be used as a typical
guideline values for preliminary engineering or in case the tie
point temperature cannot be measured.
Typical Values for RθJA in Still Air
Mounting Lead Length, L (in)
Method 1/8 1/4 1/2 3/4
θJA
152 65 72 85 °C/W
2 67 80 87 100 °C/W
3 — 50 °C/W
NOTE 4 — THERMAL CIRCUIT MODEL:
(For heat conduction through the leads)
TA(A) TA(K)
TL(A) TC(A) TJTC(K) TL(K)
PD
R
θ
S(A) R
θ
L(A) R
θ
J(A) R
θJ(K)
R
θ
L(K) R
θ
S(K)
Use of the above model permits junction to lead thermal
resistance for any mounting configuration to be found. For a
given total lead length, lowest values occur when one side of
the rectifier is brought as close as possible to the heat sink.
Terms in the model signify:
TA = Ambient Temperature TC = Case Temperature
TL = Lead Temperature TJ = Junction Temperature
RθS = Thermal Resistance, Heat Sink to Ambient
RθL = Thermal Resistance, Lead to Heat Sink
RθJ = Thermal Resistance, Junction to Case
PD = Power Dissipation
Mounting Method 1
P.C. Board with
1–1/2″ x 1–1/2″
copper surface.
Mounting Method 3
P.C. Board with
1–1/2″ x 1–1/2″
copper surface.
BOARD GROUND
PLANE
VECTOR PIN MOUNTING
Mounting Method 2
LL
LL
L = 3/8
″
(Subscripts A and K refer to anode and cathode sides,
respectively.) Values for thermal resistance components are:
RθL = 100°C/W/in typically and 120°C/W/in maximum.
RθJ = 36°C/W typically and 46°C/W maximum.
NOTE 5 — HIGH FREQUENCY OPERATION:
Since current flow in a Schottky rectifier is the result of ma-
jority carrier conduction, it is not subject to junction diode for-
ward and reverse recovery transients due to minority carrier
injection and stored charge. Satisfactory circuit analysis work
may be performed by using a model consisting of an ideal
diode in parallel with a variable capacitance. (See Figure 6.)
Rectification efficiency measurements show that operation
will be satisfactory up to several megahertz. For example,
relative waveform rectification efficiency is approximately 70
percent at 2 MHz, e.g., the ratio of dc power to RMS power in
the load is 0.28 at this frequency, whereas perfect rectifica-
tion would yield 0.406 for sine wave inputs. However, in con-
trast to ordinary junction diodes, the loss in waveform effi-
ciency is not indicative of power loss: it is simply a result of
reverse current flow through the diode capacitance, which
lowers the dc output voltage.