LMH6704 Datasheet, PDF (12/20 Pages) National Semiconductor (TI) – 650 MHz Progammable Gain Buffer with Disable

LMH6704
SNOSAD0C – FEBRUARY 2005 – REVISED MARCH 2013
www.ti.com
VIDEO PERFORMANCE
The LMH6704 has been designed to provide excellent performance with production quality video signals in a
wide variety of formats such as HDTV and High Resolution VGA. NTSC and PAL performance is nearly flawless
with DG of 0.02% and DP of 0.02°. Best performance will be obtained with back terminated loads. The back
termination reduces reflections from the transmission line and effectively masks transmission line and other
parasitic capacitances from the amplifier output stage. Figure 24 shows a typical configuration for driving a 75Ω
Cable. The amplifier is configured for a gain of two to make up for the 6 dB of loss in R_OUT.
POWER DISSIPATION
Follow these steps to determine the Maximum power dissipation for the LMH6704:
1. Calculate the quiescent (no-load) power:
P_AMP = I_CC* (V_S)
(3)
where V_S = V⁺ - V^−
2. Calculate the RMS power dissipated in the output stage:
P_D (rms) = rms ((V_S - V_OUT) x I_OUT)
(4)
where V_OUT and I_OUT are the voltage and current across the external load and V_S is the total supply current
3. Calculate the total RMS power:
P_T = P_AMP+P_D
(5)
The maximum power that the LMH6704, package can dissipate at a given temperature can be derived with the
following equation:
P_MAX = (150° – T_AMB)/ θ_JA, where T_AMB = Ambient temperature (°C) and θ_JA = Thermal resistance, from junction
to ambient, for a given package (°C/W). For the SOT-23 package θ_JA is 187°C/W.
ESD PROTECTION
The LMH6704 is protected against electrostatic discharge (ESD) on all pins. The LMH6704 will survive 2000V
Human Body model and 200V Machine model events. Input and Output pins have ESD diodes to either supply
pin (V⁺ and V^−) which are reverse biased and essentially have no effect under most normal operating conditions.
There are occasions, however, when the ESD diodes will be evident. If the LMH6704 is driven by a large signal
while the device is powered down, the ESD diodes might enter forward operating region and conduct. The
current that flows through the ESD diodes will either exit the chip through the supply pins or will flow through the
device, hence it is possible to inadvertently power up the LMH6704 with a large signal applied to the input pins.
Shorting the power pins to each other will prevent the chip from being powered up through the input.
12
Submit Documentation Feedback
Product Folder Links: LMH6704
Copyright © 2005–2013, Texas Instruments Incorporated