AD8531AR Analog Devices Inc, AD8531AR Datasheet - Page 14

• Manufacturer Part Number: AD8531AR
• Description: IC OPAMP GP R-R CMOS 3MHZ 8SOIC
• Manufacturer: Analog Devices Inc

Specifications of AD8531AR

• Rohs Status: RoHS non-compliant
• Amplifier Type: General Purpose
• Number Of Circuits: 1
• Output Type: Rail-to-Rail
• Slew Rate: 5 V/µs
• Gain Bandwidth Product: 3MHz
• Current - Input Bias: 5pA
• Voltage - Input Offset: 25000µV
• Current - Supply: 750µA
• Current - Output / Channel: 250mA
• Voltage - Supply, Single/dual (±): 2.7 V ~ 6 V, ±1.35 V ~ 3 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• -3db Bandwidth: -

AD8531/AD8532/AD8534
APPLICATIONS INFORMATION
HIGH OUTPUT CURRENT, BUFFERED
REFERENCE/REGULATOR
Many applications require stable voltage outputs relatively close
in potential to an unregulated input source. This low dropout
type of reference/regulator is readily implemented with a rail-
to-rail output op amp and is particularly useful when using a
higher current device, such as the AD8531/AD8532/AD8534.
A typical example is the 3.3 V or 4.5 V reference voltage developed
from a 5 V system source. Generating these voltages requires a
three terminal reference, such as the
REF194
outputs of 30 mA or less. Figure 42 shows how such a reference
can be outfitted with an AD8531/AD8532/AD8534 buffer for
higher currents and/or voltage levels, plus sink and source load
capability.
COMMON
The low dropout performance of this circuit is provided by
stage U2, an AD8531 connected as a follower/buffer for the
basic reference voltage produced by U1. The low voltage
saturation characteristic of the AD8531/AD8532/AD8534
allows up to 100 mA of load current in the illustrated use,
as a 5 V to 3.3 V converter with good dc accuracy. In fact,
the dc output voltage change for a 100 mA load current delta
measures less than 1 mV. This corresponds to an equivalent
output impedance of < 0.01 Ω. In this application, the stable
3.3 V from U1 is applied to U2 through a noise filter, R1 to C1.
U2 replicates the U1 voltage within a few millivolts, but at a
higher current output at V
source output current(s), unlike most IC references. R2 and C2
in the feedback path of U2 provide additional noise filtering.
Transient performance of the reference/regulator for a 100 mA
step change in load current is also quite good and is largely
determined by the R5 to C5 output network. With values as
shown, the transient is about 20 mV peak and settles to within
2 mV in less than 10 μs for either polarity. Although room exists
ON/OFF
CONTROL
INPUT CMOS HI
(OR OPEN) = ON
LO = OFF
V
V
5V
V
S
S
C
0.1µF
(4.5 V), both of which feature low power, with sourcing
C3
Figure 42. High Output Current Reference/Regulator
3
0.1µF
REF196
C1
U1
2
4
V
6
OUT2
3.3V
OUT1
=
, with the ability to both sink and
(See Text)
R1
10kΩ
1%
C4
1µF
R3
REF196
R4
3.3kΩ
10kΩ 1%
U2
AD8531
0.1µF
(3.3 V) or the
C2
R2
3.3V @ 100mA
R5
0.2Ω
C5
100µF/16V
TANTALUM
V
V
COMMON
OUT1
OUT
=
Rev. F | Page 14 of 20
for optimizing the transient response, any changes to the R5 to
C5 network should be verified by experiment to preclude the
possibility of excessive ringing with some capacitor types.
To scale V
resistor R3 (shown dotted in Figure 42) is added, causing the
new V
The circuit can either be used as shown, as a 5 V to 3.3 V
reference/regulator, or with on/off control. By driving Pin 3 of
U1 with a logic control signal as noted, the output is switched
on/off. Note that when on/off control is used, R4 must be used
with U1 to speed on/off switching.
SINGLE-SUPPLY, BALANCED LINE DRIVER
The circuit in Figure 43 is a unique line driver circuit topology
used in professional audio applications. It was modified for
automotive and multimedia audio applications. On a single 5 V
supply, the line driver exhibits less than 0.7% distortion into a
600 Ω load from 20 Hz to 15 kHz (not shown) with an input
signal level of 4 V p-p. In fact, the output drive capability of the
AD8531/AD8532/AD8534 maintains this level for loads as
small as 32 Ω. For input signals less than 1 V p-p, the THD is
less than 0.1%, regardless of load. The design is a transformer-
less, balanced transmission system where output common-
mode rejection of noise is of paramount importance. As with
the transformer-based system, either output can be shorted
to ground for unbalanced line driver applications without changing
the circuit gain of 1. Other circuit gains can be set according to the
equation in the diagram. This allows the design to be easily
configured for inverting, noninverting, or differential operation.
V
IN
SET: R7, R10, R11 = R2
SET: R6, R12, R13 = R3
A1, A2 = 1/2 AD8532
GAIN = R3
22µF
Figure 43. Single-Supply, Balanced Line Driver for Multimedia and
V
C1
OUT1
OUT1
R2
OUT2
2
3
to become
=
A1
V
5V
to another (higher) output level, the optional
OUT2
10kΩ
10kΩ
10kΩ
R1
1
R10
R2
×
⎛ +
⎜
⎝
Automotive Applications
1
R7
10kΩ
R11
10kΩ
2
3
6
5
R2
R3
A2
A2
10kΩ
⎞
⎟
⎠
R3
7
10kΩ
R12
12V
10kΩ
R13
1
7
A1
100kΩ
6
5
10kΩ
R6
R9
R14
50Ω
5V
50Ω
R5
R8
100kΩ
1µF
C2
47µF
47µF
C3
C4
600Ω
R
L
V
V
OUT2
OUT1