MAX9507 Maxim Integrated Products, MAX9507 Datasheet - Page 14

• Manufacturer Part Number: MAX9507
• Description: 1.8V DirectDrive Video Filter Amplifier
• Manufacturer: Maxim Integrated Products

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The MAX9507 contains an integrated, transparent
sync-tip clamp. When using a DC-coupled input, the
sync-tip clamp does not affect the input signal, as long
as it remains above ground. When using an AC-cou-
pled input, the sync-tip clamp automatically clamps the
input signal to ground, preventing it from going lower. A
small current of 2µA pulls down on the input to prevent
an AC-coupled signal from drifting outside the input
range of the device.
Using an AC-coupled input results in some additional
variation of the black level at the output. Applying a
voltage above ground to the input pin of the device
always produces the same output voltage, regardless
of whether the input is DC- or AC-coupled. However,
since the sync-tip clamp level (V
small range, the video black level at the output of the
device when using an AC-coupled input can vary by an
additional amount equal to the V
DC voltage gain (A
The MAX9507 has dual SPST analog switches for rout-
ing additional audio, video, digital, and other signals.
The switches are selected through the I
SW1EN (register 0x00, bit B6) and SW2EN (register
0x00, bit B7) control the analog switches. See the I
Registers and Bit Descriptions section. The dual analog
switches operate in either normal or extended range. In
normal range, the part is in shutdown and the analog
switches can handle signals between GND and V
extended range, the charge pump and linear regulator
are on and the analog switches can handle signals
between -0.9V and V
The MAX9507 typical operating circuit includes a 75Ω
back-termination resistor that limits short-circuit current
if an external short is applied to the video output. The
MAX9507 also features internal output short-circuit pro-
tection to prevent device damage in prototyping and
applications where the amplifier output can be directly
shorted.
The MAX9507 powers on in a low-power shutdown
mode with the analog switches open and the video sig-
nal path, charge pump, and load detection circuitry
disabled. It is good practice to configure the operating
1.8V DirectDrive Video Filter Amplifier with
Load Detection and Dual SPST Analog Switches
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Powering On/Off the MAX9507
Transparent Sync-Tip Clamp
V
Dual SPST Analog Switches
).
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.
Short-Circuit Protection
CLP
CLP
) can vary over a
multiplied by the
2
C interface.
DD
. In
2
C
mode of the signal path before enabling it. This may
include selecting the sync-tip clamp and video filter.
Setting CPEN = 1 (register 0x00, bit B0) enables the
charge pump. The charge pump must be fully opera-
tional before the signal path will be functional. Setting
SPEN = 1 (register 0x00, bit B1) enables the signal
path. Both SPEN and CPEN may be set at the same
time and internal control circuitry will monitor the
charge pump and enable the signal path at the appro-
priate time.
The analog switches can be turned on or off at any
time, regardless of the state of the charge pump or sig-
nal path. However, the signal range is limited from GND
to V
The MAX9507 can be placed in a low-power shutdown
mode by setting SPEN = 0 and CPEN = 0.
The MAX9507 contains video load detection circuitry at
the video output, enabling efficient power consumption
based on the actual presence of a video load. Setting
the automatic signal path enable bit, ASPEN = 1 (regis-
ter 0x01, bit B1) or the automatic charge-pump enable
bit, ACPEN = 1 (register 0x01, bit B0) enables the load
detection feature. The LOAD bit (register 0x01, bit B7)
indicates the load status.
To enable complete, automatic control of the part, set
ASPEN = ACPEN = 1 and SPEN = CPEN = 0. In this
state, when an output load is connected to the amplifi-
er, the signal path and charge pump fully turn on and
stay on until the output load is disconnected. If an out-
put load is not connected to the amplifier, then the sig-
nal path and charge pump remain in a low-power sleep
mode while continuing to check if a load is connected.
Setting SPEN = 1 or CPEN = 1 overrides the corre-
sponding ASPEN or ACPEN bits, enabling the block
regardless of the detected video load status.
The LOAD bit indicates the latest video load status. All
changes to the video load status are debounced typi-
cally 128ms to eliminate false load-detect events.
Setting the load change flag enable bit, LCFEN = 1 (reg-
ister 0x01, bit B3), and enabling the load detection fea-
ture (ASPEN = 1 or ACPEN = 1) enables the open-drain
LCF output. LCF asserts low whenever the LOAD bit
changes state. It remains low until the LOAD bit (register
0x01) is read. LCF can be used as an interrupt to notify
the system that the load status has changed.
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when the charge pump is disabled.
Video Load Detection Circuitry