Datasheet
6
7
8
5
3
2
1
4
OUT
COMP
PD
IN+
IN-
V
-
V
+
FB
V
-
DAP
V
+
1
2
3
4 5
6
7
8
PD
-IN
+IN
OUT
COMP
-
+
FB
V
-
LMH6629
SNOSB18G –APRIL 2010–REVISED MARCH 2013
www.ti.com
APPLICATION SECTION
INTRODUCTION
The LMH6629 is a high gain bandwidth, ultra low-noise voltage feedback operational amplifier. The excellent
noise and bandwidth enables applications such as medical diagnostic ultrasound, magnetic tape & disk storage
and fiberoptics to achieve maximum high frequency signal-to-noise ratios. The following discussion will enable
the proper selection of external components to achieve optimum system performance.
The LMH6629 (WSON-8 package only) has some additional features to allow maximum flexibility. As shown in
Figure 51 there are provisions for low-power shutdown and two internal compensation settings, which are further
discussed below under the COMPENSATION heading. Also provided is a feedback (FB) pin which allows the
placement of the feedback resistor directly adjacent to the inverting input (IN-) pin. This pin simplifies printed
circuit board layout and minimizes the possibility of unwanted interaction between the feedback path and other
circuit elements.
Figure 51. 8-Pin WSON Pinout Diagram
The WSON-8 package requires the bottom-side Die Attach Paddle (DAP) to be soldered to the circuit board for
proper thermal dissipation and to get the thermal resistance number specified. The DAP is tied to the V
-
potential
within the LMH6629 package. Thus, the circuit board copper area devoted to DAP heatsinking connection should
be at the V- potential as well. Please refer to the package drawing for the recommended land pattern and
recommended DAP connection dimensions.
Figure 52. WSON–8 DAP(Top View)
WSON-8 CONTROL PINS & SOT-23-5 COMPARISON
The LMH6629 WSON-8 package has two digital control pins; PD and COMP pins. The PD pin, used for
powerdown, floats high (device on) when not driven. When the PD pin is pulled low, the amplifier is disabled and
the amplifier output stage goes into a high impedance state so the feedback and gain set resistors determine the
output impedance of the circuit. The other control pin, the COMP pin, allows control of the internal compensation
and defaults to the lower gain mode or logic 0.
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