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ALD1721SA 参数 Datasheet PDF下载

ALD1721SA图片预览
型号: ALD1721SA
PDF下载: 下载PDF文件 查看货源
内容描述: EPAD ™微功耗运算放大器 [EPAD⑩ MICROPOWER OPERATIONAL AMPLIFIER]
分类和应用: 运算放大器光电二极管
文件页数/大小: 10 页 / 70 K
品牌: ALD [ ADVANCED LINEAR DEVICES ]
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errors introduced by other circuit components, such as resis-  
tor or sensor induced voltage errors, can also be corrected.  
In this way, the “in-system” circuit output can be adjusted to  
a desired level eliminating other trimming components.  
FUNCTIONAL DESCRIPTION  
TheALD1721E/ALD1721usesEPADsasin-circuitelements  
for trimming of offset voltage bias characteristics. Each  
ALD1721E/ALD1721 has a pair of EPAD-based circuits  
connected such that one circuit is used to adjust V  
direction and the other circuit is used to adjust V  
other direction.  
in one  
in the  
OS  
OS  
Functional Description of ALD1721  
The ALD1721 is pre-programmed at the factory under stan-  
dardoperatingconditionsforminimumequivalentinputoffset  
voltage. TheALD1721offerssimilarprogrammablefeatures  
as the ALD1721E, but with more limited offset voltage pro-  
gram range. It is intended for standard operational amplifier  
applications where little or no electrical programming by the  
user is necessary.  
Functional Description of ALD1721E  
While each of the EPAD devices is a monotonically adjust-  
ableprogrammabledevice,theV oftheALD1721E canbe  
OS  
adjusted many times in both directions. Once programmed,  
the set V  
levels are stored permanently, even when the  
OS  
device power is removed.  
USER PROGRAMMABLE Vos FEATURE  
The ALD1721E provides the user with an operational ampli-  
fier that can be trimmed with user application-specific pro-  
gramming or in-system programming conditions. User appli-  
cation-specific circuit programming refers to the situation  
wheretheTotalInputOffsetVoltageoftheALD1721E canbe  
trimmed with the actual intended operating conditions.  
Each ALD1721E/ALD1721 has two pins named VE1 and  
VE2 which are internally connected to an internal offset bias  
circuit. VE1/VE2 have initial typical values of 1.2 /1.7 Volt.  
ThevoltageonthesepinscanbeprogrammedusingtheALD  
E100 EPAD Programmer and the appropriate Adapter Mod-  
ule. The useful programming range of VE1 and VE2 is 1.2  
Volt to 3.0 Volts. VE1 and VE2 pins are programming pins,  
used during programming mode. The Programming pin is  
used during electrical programming to inject charge into the  
internal EPADs. Increases of VE1 decrease the offset volt-  
age while increases of VE2 increase the offset voltage of the  
operational amplifier. The injected charge is permanently  
stored and determines the offset voltage of the operational  
amplifier. After programming, VE1 and VE2 terminals must  
be left open to settle on a voltage determined by internal bias  
currents.  
The ALD1721E is pre-programmed at the factory under  
standard operating conditions for minimum equivalent input  
offset voltage. It also has a guaranteed offset voltage  
program range, which is ideal for applications that require  
electrical offset voltage programming.  
For example, an application circuit may have +6V and -2.5V  
power supplies, and the operational amplifier input is biased  
at +0.7V, and the average operating temperature is at 55°C.  
The circuit can be wired up to these conditions within an  
environmental chamber, and the ALD1721E can be inserted  
into a test socket connected to this circuit while it is being  
During programming, the voltages on VE1 or VE2 are in-  
creased incrementally to set the offset voltage of the opera-  
tionalamplifiertothedesiredV . NotethatdesiredV can  
electrically trimmed. Any error in V  
due to these bias  
OS  
conditions can be automatically zeroed out. The Total V  
OS  
OS  
OS  
error is now limited only by the adjustable range and the  
be any value within the offset voltage programmable ranges,  
and can be either zero, a positive value or a negative value.  
stability of V , and the input noise voltage of the operational  
OS  
amplifier. Therefore, this Total V  
error now includes V  
OS  
This V  
value can also be reprogrammed to a different  
OS  
is traditionally specified; plus the V error contribu-  
OS  
as V  
value at a later time, provided that the useful VE1 or VE2  
programming voltage range has not been exceeded. VE1 or  
VE2 pins can also serve as capacitively coupled input pins.  
OS  
OS  
tions from PSRR, CMRR, TCV , and noise. Typically this  
OS  
) is approximately ±35µV for the  
total V  
ALD1721E.  
error term (V  
OS  
OST  
Internally, VE1 and VE2 are programmed and connected  
differentially. Temperature drift effects between the two  
internal offset bias circuits cancel each other and introduce  
less net temperature drift coefficient change than offset  
voltage trimming techniques such as offset adjustment with  
an external trimmer potentiometer.  
The V contribution due to PSRR, CMRR, TCV  
and  
OS  
OS  
external components can be large for operational amplifiers  
without trimming. Therefore the ALD1721E with EPAD trim-  
ming is able to provide much improved system performance  
by reducing these other sources of error to provide signifi-  
cantly reduced V  
OST.  
In-System Programming refers to the condition where the  
EPAD adjustment is made after the ALD1721E has been  
inserted into a circuit board. In this case, the circuit design  
must provide for the ALD1721E to operate in normal mode  
and in programming mode. One of the benefits of in-system  
programming is that not only is the ALD1721E offset voltage  
from operating bias conditions accounted for, any residual  
While programming, V+, VE1 and VE2 pins may be alter-  
nately pulsed with 12V (approximately) pulses generated by  
theEPADProgrammer. In-systemprogrammingrequiresthe  
ALD1721E/ALD1721 application circuit to accommodate  
these programming pulses. This can be accomplished by  
adding resistors at certain appropriate circuit nodes. For  
more information, see Application Note AN1700.  
2
Advanced Linear Devices  
ALD1721E/ALD1721