LM6588MA/NOPB National Semiconductor, LM6588MA/NOPB Datasheet - Page 9

• Manufacturer Part Number: LM6588MA/NOPB
• Description: IC OPAMP TFT-LCD QUAD 16V 14SOIC
• Manufacturer: National Semiconductor
• Series: VIP10™r

Specifications of LM6588MA/NOPB

• Applications: TFT-LCD Panels: Gamma Buffer, VCOM Driver
• Output Type: Rail-to-Rail
• Number Of Circuits: 4
• -3db Bandwidth: 24MHz
• Slew Rate: 15 V/µs
• Current - Supply: 800µA
• Current - Output / Channel: 230mA
• Voltage - Supply, Single/dual (±): 5 V ~ 16 V, ±2.5 V ~ 8 V
• Mounting Type: Surface Mount
• Package / Case: 14-SOIC (0.154", 3.90mm Width)
• Number Of Channels: 4
• Voltage Gain Db: 106 dB
• Common Mode Rejection Ratio (min): 70 dB
• Input Offset Voltage: 4 mV at 5 V
• Operating Supply Voltage: 9 V, 12 V, 15 V
• Supply Current: 4 mA at 5 V
• Maximum Operating Temperature: + 85 C
• Maximum Dual Supply Voltage: +/- 8 V
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: *LM6588MA; *LM6588MA/NOPB; LM6588MA

Application Notes
CIRCUIT DESCRIPTION
GENERAL & SPEC
The LM6588 is a bipolar process operational amplifier. It has
an exceptional output current capability of 200mA. The part
has both rail to rail inputs and outputs. It has a −3dB band-
width of 24MHz. The part has input voltage noise of 23nV/
−40dB respectively.
INPUT SECTION
The LM6588 has rail to rail inputs and thus has an input
range over which the device may be biased of V
0.5V, and V
excursion is the ESD protection diodes on the input pins.
The most important consideration in Rail-to-Rail input op
amps is to understand the input structure. Most Rail-to-Rail
input amps use two differential input pairs to achieve this
function. This is how the LM6588 works. A conventional PNP
differential transistor pair provides the input gain from 0.5V
below the negative rail to about one volt below the positive
rail. At this point internal circuitry activates a differential NPN
transistor pair that allows the part to function from 1 volt
below the positive rail to 0.5V above the positive rail. The
effect on the inputs pins is as if there were two different op
amps connected to the inputs. This has several unique
implications.
It should be remembered that swinging the inputs across the
input stage transition may cause output distortion and accu-
racy anomalies. It is also worth noting that anytime any amps
inputs are swung near the rails THD and other specs are
sure to suffer.
OUTPUT SECTION
Current Rating
The LM6588 has an output current rating, sinking or sourc-
ing, of 200mA. The LM6588 is ideally suited to loads that
require a high value of peak current but only a reduced value
of average current. This condition is typical of driving the
gate of a MOSFET. While the output drive rating is 200mA
peak, and the output structure supports rail-to-rail operation,
the attainable output current is reduced when the gain and
drive conditions are such that the output voltage approaches
either rail.
• The input offset voltage will change, sometimes from
• The input bias currents can be either positive or negative.
• The part will have different specifications depending on
• There is a little more input capacitance then a single
• Since the input offset voltages can change from positive
positive to negative as the inputs transition between the
two stages at about a volt below the positive rail. this
effect is seen in the V
Performance Characteristics section of this datasheet.
Do not expect a consistent flow in or out of the pins.
whether the NPN or PNP stage is operating.
stage input although the ESD diodes often swamp out the
added base capacitance.
to negative the output may not be monotonic when the
inputs are transitioning between the two stages and the
part is in a high gain configuration.
, and 2
+
nd
plus 0.5V. The ultimate limit on input voltage
and 3
rd
harmonic distortion of −53dB and
OS
vs. V
CM
chart in the Typical
−
minus
9
Output Power
Because of the increased output drive capability, internal
heat dissipation must be held to a level that does not in-
crease the junction temperature above its maximum rated
value of 150˚ C.
Power Requirements
The LM6588 operates from a voltage supply, of V
ground, or from a V
voltage range is +5V to +16V and split supply range is
to
APPLICATION HINTS
POWER SUPPLIES
Sequencing
Best practice design technique for operational amplifiers
includes careful attention to power sequencing. Although the
LM6588 is a bipolar op amp, recommended op amp turn on
power sequencing of ground (or V
lowed by input signal should be observed. Turn off power
sequence should be the reverse of the turn-on sequence.
Depending on how the amp is biased the outputs may swing
to the rails on power-on or power-off. Due to the high output
currents and rail to rail output stage in the LM6588 the output
may oscillate very slightly if the power is slowly raised be-
tween 2V and 4V The part is unconditionally stable at 5V.
Quick turn-off and turn-on times will eliminate oscillation
problems.
PSRR and Noise
Care should be taken to minimize the noise in the power
supply rails. The figure of merit for an op amp’s ability to
keep power supply noise out of the signal is called Power
Supply Rejection Ratio (PSRR). Observe from the PSRR
charts in the Typical Performance Characteristics section
that the PSRR falls of dramatically as the frequency of the
noise on the power supply line goes up. This is one of the
reasons switching power supplies can cause problems. It
should also be noticed from the charts that the negative
supply pin is far more susceptible to power noise. The de-
sign engineer should determine the switching frequencies
and ripple voltages of the power supplies in the system. If
required, a series resistor or in the case of a high current op
amp like the LM6588, a series inductor can be used to filter
out the noise.
Transients
In addition to the ripple and noise on the power supplies
there are also transient voltage changes. This can be
caused by another device on the same power supply sud-
denly drawing current or suddenly stopping a current draw.
The design engineer should insure that there are no damag-
ing transients induced on the power supply lines when the op
amp suddenly changes current delivery.
LAYOUT
Ground Planes
Do not assume the ground (or more properly, the common or
return) of the power supply is an ocean of zero impedance.
The thinner the trace, the higher the resistance. Thin traces
cause tiny inductances in the power lines. These can react
against the large currents the LM6588 is capable of deliver-
ing to cause oscillations, instability, overshoot and distortion.
A ground plane is the most effective way of insuring the
±
8.0V.
−
and V
+
split supply. Single-ended
−
), followed by V
www.national.com
±
+
+
, fol-
2.5V
and