TS12012ITD1022 datasheet(11/18 Pages) SILABS

tên linh kiện	TS12012ITD1022

Giải thích chi tiết về linh kiện	Nanopower Op Amp, Comparator, and Reference

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TS12011/TS12012

TS12011/12 Rev. 1.0

Page 11

Adding Hysteresis to the TS12011 Push-pull

Output Option

Additional hysteresis can be generated with three

external resistors using positive feedback as shown

in Figure 2. Unfortunately, this method also reduces

the hysteresis response time. The procedure to

calculate the resistor values for the TS12011 is as

follows:

1)

Setting R2. As the leakage current at the IN

pin is less than 20nA, the current through R2

should be at least 150nA to minimize offset

voltage errors caused by the input leakage

current. The current through R2 at the trip

point is (VREFOUT - VCOMPOUT)/R2.

In solving for R2, there are two formulas –

one each for the two possible output states:

R2 = VREFOUT/IR2

or

R2 = (VDD - VREFOUT)/IR2

From the results of the two formulae, the

smaller of the two resulting resistor values is

chosen.

For

example,

when

using

the

TS12011 (VREFOUT = 0.58V) at a VDD = 2.5V

and if IR2 = 150nA is chosen, then the

formulae above produce two resistor values:

3.87M

Ω and 12.8MΩ - a 4.02MΩ standard

value for R2 is selected.

2)

Next, the desired hysteresis band (VHYSB) is

set. In this example, VHYSB is set to 100mV.

3)

Resistor R1 is calculated according to the

following equation:

R1 = R2 x (VHYSB/VDD)

and substituting the values selected in 1) and

2) above yields:

R1 = 4.02M

Ω x (100mV/2.5V) = 160.8kΩ.

The 160k

Ω standard value for R1 is chosen.

4)

The trip point for COMPIN+ rising (VTHR) is

chosen such that VTHR > VREFOUT x (R1 +

R2)/R2 (VTHF is the trip point for VCOMPIN+

falling). This is the threshold voltage at which

the comparator switches its output from low

to high as VCOMPIN+ rises above the trip point.

In this example, VTHR is set to 2.

5)

With the VTHR from Step 4 above, resistor R3

is then computed as follows:

R3 = 1/[VTHR/(VREFOUT x R1) - (1/R1) - (1/R2)]

R3 = 1/[2V/(0.58V x 160k

Ω) - (1/160kΩ) -

(1/4.02M

Ω)] = 66.43kΩ

In this example, a 69.8k

Ω, 1% standard

value resistor is selected for R3.

6)

The last step is to verify the trip voltages and

hysteresis

band

using

the

standard

resistance values:

For VCOMPIN+ rising:

VTHR = VREFOUT x R1 [(1/R1) + (1/R2) + (1/R3)]

= 1.93V

For VCOMPIN+ falling:

VTHF = VTHR - (R1 x VDD/R2) = 1.83V

and Hysteresis Band = VTHR – VTHF = 100mV

Figure 2. Using Three Resistors Introduces

Additional Hysteresis in the TS12011

Figure 1. TS12011/TS12012 Threshold

Hysteresis Band

Số phần tương tự - TS12012ITD1022

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