LTC2966 datasheet(13/20 Pages) LINER

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LTC2966

2966fc

For more information www.linear.com/LTC2966

APPLICATIONS INFORMATION

current specifications. When the status outputs are low,

power is dissipated in the pull-up resistors. An internal

pull-up is present if the OUT pins are left floating or if

low power consumption is required. The internal pull-up

resistor does not draw current if an external resistor pulls

OUT up to a voltage greater than VOH.

If PS is connected to ground, the comparator output is

noninverting. This means that OUT pulls low when VIN

falls below the scaled INL voltage. OUT is released after

VIN rises above the scaled INH voltage. Likewise, if PS

is connected to REF or a voltage >VTH, the comparator

output is inverting. This means that OUT pulls low when

VIN rises above the scaled INH voltage and is released

when VIN falls below the scaled INL voltage.

If both VIN pins fall below the UVLO threshold minus hys-

teresis, the outputs are pulled to ground. The outputs are

guaranteed to stay low for VINA ≥ VINB ≥ 1.25V regardless

of the output logic configuration.

It is recommended that circuit board traces associated

with the OUT pin be located on a different layer than those

associated with the INH/INL and REF pins where possible

to avoid capacitive coupling.

Hot Swap Events

The LTC2966 can withstand high voltage transients up

to 140V. However, when a supply voltage is abruptly

connected to the input resonant ringing can occur as a

result of series inductance. The peak voltage could rise

to 2x the input supply, but in practice can reach 2.5x if

a capacitor with a strong voltage coefficient is present.

Circuit board trace inductances of as little as 10nH can

produce significant ringing. Ringing beyond the absolute

maximum specification can be destructive to the part and

shouldbeavoidedwheneverpossible.Oneeffectivemeans

to eliminate ringing seen at the VIN pins and to protect the

part is to include a 1kΩ to 5kΩ resistance between the

monitored voltage and the VIN pin as shown in Figure 6.

This provides damping for the resonant circuit. If there

is a decoupling capacitor on the VINA/VINB pins the time

constant formed by the RC network should be considered.

Figure 4. Reducing VIN Threshold Error

Figure 5. Disabling a Channel

Disabling a Channel

Figure 5 shows the proper technique for disabling a chan-

nel.Table4summarizesthecorrectconnections.Correctly

disabling an unused channel prevents its comparator

output from chattering and introducing unwanted noise

in the system.

Table 4. Disabling a Channel

CONNECT TO

VIN

GND

INH

REF

INL

GND

RS1

GND or REF

RS2

GND or REF

OUT

Open

VIN

LTC2966

GND

REF

1µF

INH

INL

2966 F04

LT6656-2.048

OUT

200k

0.1%

1.8M

0.1%

47.5k

0.1%

10k

GND

Output Configuration with Polarity Selection

TheOUTpinmaybeusedwithawiderangeofuser-defined

voltages up to 100V with an external resistor. Select a

resistor compatible with desired output rise time and load

VINA

GND

1/2 LTC2966

OPEN

REF

INHA

INLA

OUTA

RS1A

RS2A

PSA

OPEN

2966 F05

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