TS12012ITD1022T datasheet(7/11 Pages) TOUCHSTONE

Teilenummer	TS12012ITD1022T

Bauteilbeschribung	A 0.8V/1.5uA Nanopower Op Amp, Comparator, and Reference

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Hersteller	TOUCHSTONE [Touchstone Semiconductor Inc]

Direct Link	http://www.touchstonesemi.com

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TS12011/TS12012

TS12011_12DS r1p0

Page 7

RTFDS

input offset current are less than 20nA and 2nA,

respectively.

Comparator

The TS12011 and TS12012 analog comparator input

stage is robust as it can tolerate input voltages

300mV beyond the power supply rails. To insure

clean

output

switching

behavior,

the

analog

comparator features ±7.5mV internal hysteresis. The

TS12011 push-pull output driver was designed to

minimize supply-current surges while driving ±100µA

loads with an output swing to within 100mV of the

supply rails. The open drain output stage TS12012

can be connected to supply voltages above VDD to an

absolute maximum of 5.5V above VSS. Where wired-

OR logic connections are needed, the open-drain

output stage makes it easy to use this analog

comparator. The TS12011 and the TS12012 can sink

0.5mA and 1.4mA of current, respectively. The

TS12011 can source 0.1mA of current.

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 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

100kΩ//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

10MΩ 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

is

a

well-established

technique

to

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.

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:

Figure 1. TS12011/TS12012 Threshold

Hyesteresis Band

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