ISL59830_14 Datasheet, PDF (10/14 Pages) Intersil Corporation – True Single Supply Video Driver

Demo Board Schematic
ISL59830
RED_IN
R₁
75Ω
GREEN_IN
R₂
75Ω
BLUE_IN
R₃
75Ω
C₄
1.0µF
1 RIN
2 GIN
3 BIN
R₇
4 REF
1kΩ
5 VEE
ROUT 16
GOUT 15
BOUT 14
VCC 13
EN 12
R₄ 75Ω
R₅ 75Ω
R₆ 75Ω
V_CC
C₃
0.1µF
RED_OUT
GREEN_OUT
BLUE_OUT
V_CC
R₄
499Ω
R₈
1kΩ
V_CC
C₂
0.1µF
6 GND
VCC 11
7 VEEOUT NC 10
8 DGND DVCC 9
ENABLE
2
1
C₅ 0.1µF
3
V_CC
REFERENCE
CONTROL
D₁
1N4148
(or similar)
Option: Panasonic 120Ω Bead
EXC3BP121H
Lower Amp output noise from charge pump
Description of Operation and Application
Information
Theory Of Operation
The ISL59830 is a highly practical and robust marriage of
three high bandwidth, high speed, low power, rail-to-rail
voltage feedback amplifiers with a charge pump, to provide a
negative rail without an additional power supply. Designed to
operate with a single supply voltage range of from 0V to
3.3V, the ISL59830 eliminates the need for a split supply with
the incorporation of a charge pump capable of generating a
bottom rail as much as 1.6V below ground; for a 4.9V range
on a single 3.3V supply. This performance is ideal for NTSC
video with its negative-going sync pulses.
The Amplifier
The ISL59830 fabricated on a dielectrically isolated high
speed 5V Bi-CMOS process with 4GHz PNPs and NPN
transistor exceeding 20GHz - perfect for low distortion, low
power demand and high frequency circuits. While the
ISL59830 utilizes somewhat standard voltage mode
feedback topologies, there are many non-standard analog
features providing its outstanding bandwidth, rail-to-rail
operation, and output drive capabilities. The input signal
initially passes through a folded cascode, a topology
providing enhanced frequency response essentially by fixing
the base collector voltage at the junction of the input and
gain stage. The collector of each input device looks directly
into an emitter that is tied closely to ground through a
resistor and biased with a very stable DC source. Since the
voltage of this collector is "locked stable" the effective
10
bandwidth limiting of the Miller capacitance is greatly
reduced. The signal is then passed through a second fully-
realized differential gain stage and finally through a
proprietary common emitter output stage for improved rail-
to-rail output performance. The result is a highly-stable, low
distortion, low power, and high frequency amplifier capable
of driving moderately capacitive loads with near rail-to-rail
performance.
Input Output Range
The three amplifier channels have an input common mode
voltage range from 0.15V below the bottom rail to within
100mV of the positive supply, V_S+ pin (Note: bottom rail is
established by the charge pump at negative one half the
positive supply). As the input signal moves outside the
specified range, the output signal will exhibit increasingly
higher levels of harmonic distortion. And of course, as load
resistance becomes lower, the current drive capability of the
device will be challenged and its ability to drive close to each
rail is reduced. For instance, with a load resistance of 1kΩ
the output swing is within a 100mV of the rails, while a load
resistance of 150Ω limits the output swing to within around
300mV of the rails.
Amplifier Output Impedance
To achieve near rail-to-rail performance, the output stage of
the ISL59830 uses transistors in the common emitter
configuration, typically producing higher output impedance
than the standard emitter follower output stage. The
exceptionally high open loop gain of the ISL59830 and local
feedback reduces output impedance to less than a 2Ω at low
frequency. However, since output impedance of the device is
FN7489.6
May 4, 2006