LPV521 datasheet(20/34 Pages) TI1

20 / 34 page

VIN

RISO

VOUT

LPV521

SNOSB14D – AUGUST 2009 – REVISED DECEMBER 2014

www.ti.com

8 Applications and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

The LPV521is specified for operation from 1.6 V to 5.5 V (±0.8 V to ±2.25 V). Many of the specifications apply

from –40°C to 125°C. The LMV521 features rail to rail input and rail-to-rail output swings while consuming only

nanowatts of power. Parameters that can exhibit significant variance with regard to operating voltage or

temperature are presented in the Typical Characteristics section.

8.1.1 Driving Capacitive Load

The LPV521 is internally compensated for stable unity gain operation, with a 6.2-kHz, typical gain bandwidth.

However, the unity gain follower is the most sensitive configuration to capacitive load. The combination of a

capacitive load placed at the output of an amplifier along with the amplifier’s output impedance creates a phase

lag, which reduces the phase margin of the amplifier. If the phase margin is significantly reduced, the response

will be under damped which causes peaking in the transfer and, when there is too much peaking, the op amp

might start oscillating.

Figure 62. Resistive Isolation of Capacitive Load

In order to drive heavy capacitive loads, an isolation resistor, RISO, should be used, as shown in Figure 62. By

using this isolation resistor, the capacitive load is isolated from the amplifier’s output. The larger the value of

RISO, the more stable the amplifier will be. If the value of RISO is sufficiently large, the feedback loop will be

stable, independent of the value of CL. However, larger values of RISO result in reduced output swing and

reduced output current drive.

Recommended minimum values for RISO are given in the following table, for 5-V supply. Figure 63 shows the

typical response obtained with the CL = 50 pF and RISO = 154 kΩ. The other values of RISO in the table were

chosen to achieve similar dampening at their respective capacitive loads. Notice that for the LPV521 with larger

CL a smaller RISO can be used for stability. However, for a given CL a larger RISO will provide a more damped

response. For capacitive loads of 20 pF and below no isolation resistor is needed.

RISO

0 – 20 pF

not needed

50 pF

154 k

Ω

100 pF

118 k

Ω

500 pF

52.3 k

Ω

1 nF

33.2 k

Ω

5 nF

17.4 k

Ω

10 nF

13.3 k

Ω

Submit Documentation Feedback

Product Folder Links: LPV521

LPV521 датащи(PDF) 20 Page - Texas Instruments

LPV521 датащи(HTML) 20 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34

датащи скачать

ссылки URL