TS12011 datasheet(10/18 Pages) SILABS

10 / 18 page

TS12011/TS12012

Page 10

TS12011/12 Rev. 1.0

change, the comparator stays active and waits for the

crossing, at which point it will latch in its final state.

An internal POR circuit ensures that the latch powers

up in the “comparator active” state if LHDET

is low

when VDD is first applied.

Latch Truth Table – TS12011

LHDET

CMPOUT

initial

state

CMPIN+

to CMPIN-

difference

voltage

CMPOUT

HIGH

N/A

Normal

operation

LOW

HIGH

(latched)

LOW

negative

LOW

(comparator

active)

LOW

positive

HIGH

(latched)

X = Don’t Care

Latch Truth Table – TS12012

LHDET

CMPOUT

initial

state

CMPIN+

to CMPIN-

difference

voltage

CMPOUT

HIGH

N/A

Normal

operation

LOW

(latched)

LOW

HIGH

positive

HIGH

(comparator

active)

LOW

HIGH

negative

LOW

(latched)

X = Don’t Care

Reference

The TS12011 and TS12012 on-board 0.58V ±4.5%

reference voltage can source and sink 0.1µA and

0.1µA of current and can drive a capacitive load less

than 50pF and greater than 50nF with a maximum

capacitive load of 250nF. The higher the capacitive

load, the lower the noise on the reference voltage

and the longer the time needed for the reference

voltage to respond and become available on the

REFOUT pin. With a 250nF capacitive load, the

reference voltage will settle to within specifications in

approximately 20ms.

Op Amp

The TS12011 and TS12012 have a unity-gain stable

op-amp with a GBWP of 15kHz, a slew rate of 6V/ms,

and can drive a capacitive load up to 50pF. The

common mode input voltage range extends from VSS

to VDD and the input bias current and offset current

are less than 20nA and 2nA, respectively.

Op-Amp Stability

The TS12011 and TS12012 op-amp is able to drive

up to 50pF of capacitive load and still maintain

stability in a unity-gain configuration with a 15kHz

GBWP and a phase margin of 70 degrees with a

100k

Ω//20pF output load.

Though the TS12011 and TS12012 address low

frequency applications, it is essential to perform good

layout techniques in order to minimize board leakage

and stray capacitance, which is of a concern in low

power, high impedance circuits. For instance, a

10M

Ω resistor coupled with a 1pF stray capacitance

can lead to a pole at approximately 15kHz, which is

the GBWP of the device. If stray capacitance is

unavoidable, a feedback capacitor can be placed in

parallel with the feedback resistor.

APPLICATIONS INFORMATION

Comparator Hysteresis

As a result of circuit noise or unintended parasitic

feedback, many analog comparators often break into

oscillation within their linear region of operation

especially when the applied differential input voltage

approaches 0V (zero volt). Externally-introduced

hysteresis

well-established

technique

for

stabilizing analog comparator behavior and requires

external components. As shown in Figure 1, adding

comparator hysteresis creates two trip points: VTHR

(for the rising input voltage) and VTHF (for the falling

input voltage). The hysteresis band (VHB) is defined

as the voltage difference between the two trip points.

When a comparator’s input voltages are equal,

hysteresis effectively forces one comparator input to

move quickly past the other input, moving the input

out of the region where oscillation occurs. Figure 1

illustrates the case in which an IN- input is a fixed

voltage and an IN+ is varied. If the input signals were

reversed, the figure would be the same with an

inverted output. To save cost and external pcb area,

an internal ±7.5mV hysteresis circuit was added to

the TS12011 and TS12012.

TS12011 Datasheet(PDF) 10 Page - Silicon Laboratories

TS12011 Datasheet(HTML) 10 Page - Silicon Laboratories

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Datasheet Download

Link URL