AD8629D703L View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
AD8629D703L Datasheet PDF : 8 Pages
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AD8629S
both auto-zeroing and chopping in a patented ping-pong arrangement to obtain lower low frequency noise
together with lower energy at the chopping and auto-zeroing frequencies, maximizing the signal-to-noise ratio
for the majority of applications without the need for additional filtering. The relatively high clock frequency of
15 kHz simplifies filter requirements for a wide, useful noise-free bandwidth.
The AD8629 has low noise over a relatively wide bandwidth (0 Hz to 10 kHz) and can be used where the
highest dc precision is required. In systems with signal bandwidths of from 5 kHz to 10 kHz, the AD8629
provides true 16-bit accuracy, making it the best choice for very high resolution systems.
7.2. Input Overvoltage Protection
Although the AD8629 are rail-to-rail input amplifiers, care should be taken to ensure that the potential
difference between the inputs does not exceed the supply voltage. Under normal negative feedback operating
conditions, the amplifier corrects its output to ensure that the two inputs are at the same voltage. However, if
either input exceeds either supply rail by more than 0.3 V, large currents begin to flow through the ESD
protection diodes in the amplifier.
These diodes are connected between the inputs and each supply rail to protect the input transistors against
an electrostatic discharge event, and they are normally reverse-biased. However, if the input voltage exceeds
the supply voltage, these ESD diodes can become forward-biased. Without current limiting, excessive
amounts of current could flow through these diodes, causing permanent damage to the device. If inputs are
subject to overvoltage, appropriate series resistors should be inserted to limit the diode current to less than 5
mA maximum.
7.3. Output Phase Reversal
Output phase reversal occurs in some amplifiers when the input common-mode voltage range is exceeded.
As common-mode voltage is moved outside the common-mode range, the outputs of these amplifiers can
suddenly jump in the opposite direction to the supply rail. This is the result of the differential input pair shutting
down, causing a radical shifting of internal voltages that result in the erratic output behavior.
The AD8629 amplifiers have been carefully designed to prevent any output phase reversal, provided that both
inputs are maintained within the supply voltages. If one or both inputs could exceed either supply voltage, a
resistor should be placed in series with the input to limit the current to less than 5 mA. This ensures that the
output does not reverse its phase.
7.4. Overload Recovery Time
Many auto-zero amplifiers are plagued by a long overload recovery time, often in ms, due to the complicated
settling behavior of the internal nulling loops after saturation of the outputs. The AD8629 has been designed
so that internal settling occurs within two clock cycles after output saturation occurs. This results in a much
VKRUWHUUHFRYHU\WLPHOHVVWKDQȝVZKHQFRPSDUHGWRRWKHUDXWR-zero amplifiers. The wide bandwidth of
the AD8629 enhances performance when the parts are used to drive loads that inject transients into the
outputs. This is a common situation when an amplifier is used to drive the input of switched capacitor ADCs.
ORDERING GUIDE
Model
Temperature Range Package Description Package Option
AD8629D703L –55°C to +125°C
10 Pin Dual Flat Pack GDFP1-F10
ASD0016529 Rev. E | Page 7 of 8
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