Datasheet
MCP631/2/3/4/5/9
DS22197B-page 22 2009-2011 Microchip Technology Inc.
4.2 Rail-to-Rail Output
4.2.1 MAXIMUM OUTPUT VOLTAGE
The Maximum Output Voltage (see Figure 2-16 and
Figure 2-17) describes the output range for a given
load. For instance, the output voltage swings to within
50 mV of the negative rail with a 1 k load tied to V
DD
/
2.
4.2.2 OUTPUT CURRENT
Figure 4-4 shows the possible combinations of output
voltage (V
OUT
) and output current (I
OUT
), when
V
DD
= 5.5V. I
OUT
is positive when it flows out of the op
amp into the external circuit.
FIGURE 4-4: Output Current.
4.2.3 POWER DISSIPATION
Since the output short circuit current (I
SC
) is specified
at ±70 mA (typical), these op amps are capable of both
delivering and dissipating significant power.
Figure 4-5 shows the quantities used in the following
power calculations for a single op amp. R
SER
is 0 in
most applications; it can be used to limit I
OUT
. V
OUT
is
the op amp’s output voltage, V
L
is the voltage at the
load, and V
LG
is the load’s ground point. V
SS
is usually
ground (0V). The input currents are assumed to be
negligible. The currents shown are approximately:
EQUATION 4-1:
FIGURE 4-5: Diagram for Power
Calculations.
The instantaneous op amp power (P
OA
(t)), R
SER
power
(P
RSER
(t)) and load power (P
L
(t)) are:
EQUATION 4-2:
The maximum op amp power, for resistive loads,
occurs when V
OUT
is halfway between V
DD
and V
LG
or
halfway between V
SS
and V
LG
:
EQUATION 4-3:
The maximum ambient to junction temperature rise
(T
JA
) and junction temperature (T
J
) can be calculated
using P
OAmax
, ambient temperature (T
A
), the package
thermal resistance (
JA
) found in Table 1 -4, and the
number of op amps in the package (assuming equal
power dissipations):
EQUATION 4-4:
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
-120
-100
-80
-60
-40
-20
0
20
40
60
80
100
120
I
OUT
(mA)
V
OUT
(V)
R
L
= 10Ω
R
L
= 100Ω
R
L
= 1 kΩ
V
OH
Limited
V
OL
Limited
-I
SC
Limited
+I
SC
Limited
(V
DD
= 5.5V)
V
OUT
–V
LG
I
OUT
=I
L
=
R
SER
+R
L
I
DD
I
Q
+max(0,I
OUT
)
I
SS
–I
Q
+min(0,I
OUT
)
Where:
I
Q
= quiescent supply current
V
DD
V
L
R
L
V
LG
I
DD
I
SS
I
L
I
OUT
R
SER
V
OUT
V
SS
MCP63X
P
OA
(t) = I
DD
(V
DD
–V
OUT
)+I
SS
(V
SS
–V
OUT
)
P
RSER
(t) = I
OUT
2
R
SER
P
L
(t) = I
L
2
R
L
P
OAmax
max
2
(V
DD
–V
LG
,V
LG
–V
SS
)
4(R
SER
+R
L
)
T
JA
=P
OA
(t)
JA
nP
OAmax
JA
T
J
=T
A
+
T
JA
Where:
n = number of op amps in package (1, 2)