TSC2010H_V01 datasheet(32/49 Pages) STMICROELECTRONICS

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5.7

Shutdown mode

If the SHDN pin is driven between 0.7 x Vcc and Vcc the TSC2011H enters low power shutdown mode, drawing

less than 20 µA, over the Vcc and Vicm range. In SHDN mode the output is in HiZ state.

Although there is an internal current source of 500 nA on the SHDN pin, keeping a low state allowing the

TSC2011H to work without any voltage applied on the SHDN pin, it is strongly recommended to apply the

dedicated voltage on the SHDN pin to ensure the full functionality of the TSC2011H, especially when fast

common mode variation appears.

The figure below depicts the architecture of the SHDN pin.

Figure 64. SHDN pin

•

With GND applied to SHDN pin the TSC2011H is in active mode

•

With Vcc applied to SHDN pin the TSC2011H is in shutdown mode

5.8

Stability

•

Driving switched capacitive loads

Some ADCs get their signal thanks to a sample and hold capacitor. If before a sampling this capacitance is fully

discharged, a fast current load can appear on the output of the TSC2011H during the sampling phase.

The scope probe in the figure below shows the output voltage of the TSC2011H excited by a 40 pF capacitor with

a 3.3 Vpp signal at 50 kHz to simulate the sample and hold circuit of the ADC120.

Figure 65. Capacitive load response at Vcc = 3.3 V

-4µ

4µ

8µ

12µ

-8

-7

-6

-5

-4

-3

-2

-1

-1000

-900

-800

-700

-600

-500

-400

-300

-200

-100

100

200

300

400

500

600

700

800

900

1000

Time (s)

Sample and hold

Vout

Vcc=3.3V, Vicm=1.65V, Vsense=0Vpp

T=25°C,

50kHz square signal of 3.3V amplitude

injected in the output through 40pF

The ADC120 has a conversion rate of 50 ksps, which is perfect to sample and hold the output of the TSC2011H

without any error.

The following graph shows the behavior of the output of the TSC2011H under the worst case condition, as for

example, when there is an ADC120 channel change between two measurements.

TSC2010H, TSC2011H, TSC2012H

Application information

DS13791 - Rev 2

page 32/49

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