Figure 4-7 shows a capacitive load (C
參數(shù)資料
型號: MCP621ST-E/OT
廠商: Microchip Technology
文件頁數(shù): 19/66頁
文件大?。?/td> 0K
描述: IC OPAMP SGL 2.5MA 20MHZ SOT23-5
標(biāo)準(zhǔn)包裝: 1
系列: mCal 技術(shù)
放大器類型: 通用
電路數(shù): 1
輸出類型: 滿擺幅
轉(zhuǎn)換速率: 10 V/µs
增益帶寬積: 20MHz
電流 - 輸入偏壓: 5pA
電壓 - 輸入偏移: 200µV
電流 - 電源: 2.5mA
電流 - 輸出 / 通道: 70mA
電壓 - 電源,單路/雙路(±): 2.5 V ~ 5.5 V
工作溫度: -40°C ~ 125°C
安裝類型: 表面貼裝
封裝/外殼: SC-74A,SOT-753
供應(yīng)商設(shè)備封裝: SOT-23-5
包裝: 標(biāo)準(zhǔn)包裝
其它名稱: MCP621ST-E/OTDKR
MCP621/1S/2/3/4/5/9
DS22188C-page 26
2009-2011 Microchip Technology Inc.
Figure 4-7 shows a capacitive load (CL), which is
driven by a sine wave with DC offset. The capacitive
load causes the op amp to output higher currents at
higher frequencies. Because the output rectifies IOUT,
the op amp’s dissipated power increases (even though
the capacitor does not dissipate power).
FIGURE 4-8:
Diagram for Capacitive Load
Power Calculations.
The output voltage is assumed to be:
EQUATION 4-4:
The op amp’s currents are:
EQUATION 4-5:
The op amp’s instantaneous power, average power
and peak power are:
EQUATION 4-6:
The power dissipated in a package depends on the
powers dissipated by each op amp in that package:
EQUATION 4-7:
The maximum ambient-to-junction temperature rise
(
ΔTJA) and junction temperature (TJ) can be calculated
using the maximum expected package power (PPKG),
ambient temperature (TA) and the package thermal
resistance (
θJA) found in Table 1-4:
EQUATION 4-8:
The worst-case power derating for the op amps in a
particular package can be easily calculated:
EQUATION 4-9:
Several techniques are available to reduce
ΔTJA for a
given package:
Reduce
θJA
- Use another package
- Improve the PCB layout (ground plane, etc.)
- Add heat sinks and air flow
Reduce max (PPKG)
- Increase RL
- Decrease CL
- Limit IOUT using RISO (see Figure 4-9)
- Decrease VDD
CL
VDD
VOUT
IDD
ISS
IOUT
VSS
MCP62X
V
OUT
V
DC
V
AC
ωt
()
sin
+
=
Where:
VDC = DC offset (V)
VAC = Peak output swing (VPK)
ω = Radian frequency (2π f) (rad/s)
I
OUT
C
L
dV
OUT
dt
-----------------
V
ACωCL
ωt
()
cos
==
I
DD
I
Q
max 0 I
OUT
,
()
+
I
SS
I
Q
min 0 I
OUT
,
()
+
Where:
IQ = Quiescent supply current for one op
amp (mA/amplifier)
P
OA
I
DD VDD
V
OUT
() I
SS VSS
V
OUT
()
+
=
ave P
OA
()
V
DD
V
SS
() I
Q
4V
AC fCL
π
------------------------
+
=
max P
OA
()
V
DD
V
SS
() I
Q
2V
AC fCL
+
()
=
P
PKG
P
OA
k1
=
n
=
Where:
n = Number of op amps in package (1 or 2)
ΔT
JA
P
PKGθJA
=
T
J
T
A
ΔT
JA
+
=
P
PKG
T
Jmax
T
A
θ
JA
--------------------------
Where:
TJmax = Absolute maximum junction
temperature (°C)
TA = Ambient temperature (°C)
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