Datasheet
MCP660/1/2/3/4/5/9
DS22194D-page 22 2009-2012 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 example, 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 ±90 mA (typical), these op amps are capable of both
delivering and dissipating significant power.
FIGURE 4-5: Diagram for Power
Calculations.
Figure 4-5 shows the power calculations used for a sin-
gle op amp:
•R
SER
is 0 in most applications, and can be used
to limit I
OUT
.
•V
OUT
is the op amp’s output voltage.
•V
L
is the voltage at the load.
•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 in Figure 4-5 can be approximated
using Equation 4-1:
EQUATION 4-1:
The instantaneous op amp power (P
OA
(t)), R
SER
power
(P
RSER
(t)) and load power (P
L
(t)) are calculated in
Equation 4-2:
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 Ta bl e 1 -4 ), and the
number of op amps in the package (assuming equal
power dissipations), as shown in Equation 4-4:
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
DD
V
L
R
L
V
LG
I
DD
I
SS
I
L
I
OUT
R
SER
V
OUT
V
SS
MCP66X
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
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
SS
)
4(R
SER
+ R
L
)
T
JA
= P
OA
(t)
JA
n P
OAmax
JA
T
J
= T
A
+
T
JA
Where:
n = number of op amps in package (1, 2)