LT2940CMS datasheet(8/24 Pages) LINER

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LT2940

2940f

PIN FUNCTIONS

CMPOUT (Pin 1): Inverting Open-Collector Comparator

Output. When the LATCH pin’s state does not override the

comparator, CMPOUT pulls low when CMP+ > 1.24V. The

pull-down shuts off when CMP+ < 1.21V, or VCC < 2.5V or

when the LATCH pin is low. CMPOUT may be pulled up to

36V maximum. Do not sink more than 22mA DC.

CMPOUT (Pin 2): Noninverting Open-Collector Comparator

Output. When the LATCH pin’s state does not override the

comparator, CMPOUT pulls low when CMP+ < 1.21V, or

VCC < 2.5V, or when the LATCH pin is low. The pull-down

shuts off when CMP+ > 1.24V. CMPOUT may be pulled up

to 36V maximum. Do not sink more than 22mA DC.

CMP+ (Pin 3): Positive Comparator Input. The integrated

comparator resolves to high when the pin voltage exceeds

the 1.24V internal reference. The comparator input has

35mV of negative hysteresis, which makes its falling trip

point approximately 1.21V. Do not exceed 36V. Tie CMP+

to GND if unused.

PMON (Pin 4): Proportional-to-Power Monitor Output. This

push-pull output sources or sinks a current proportional

to the product of the voltage sense and current sense

inputs. A resistor from PMON to GND creates a positive

voltage when the power product is positive. The full-scale

output of ±200μA is generated for a sense input product

of ±0.4V2. Do not exceed VCC + 1V, up to 16V maximum.

Tie PMON to GND if unused.

IMON (Pin 5): Proportional-to-Current Monitor Output.

This push-pull output sources or sinks a current propor-

tional to the voltage at the current sense input, which is

typically generated by a sense resistor that measures a

current. A resistor from IMON to GND creates a positive

voltage when the sensed current is positive. The full-scale

output of ±200μA is generated by a current sense input

of ±200mV. Do not exceed VCC + 1V, up to 16V maximum.

Tie IMON to GND if unused.

GND (Pin 6): Device Ground.

V+, V– (Pins 8, 7): Voltage Sense Inputs. The voltage

difference between these pins is the voltage input factor

to the power calculation multiplier. The difference may be

positive or negative, but both pin voltages must be at or

above GND – 100mV. The input differential voltage range

is ±8V. Do not exceed 36V on either pin.

LATCH (Pin 9): Comparator Mode Input. Conditions at this

three-state input pin control the comparator’s behavior.

When LATCH is open, the comparator’s outputs track its

input conditions (with hysteresis). When LATCH is held

above 2.5V, the comparator’s outputs latch when CMP+

exceeds 1.24V (CMPOUT open,CMPOUT pull-down). While

LATCH ≤ 0.5V or VCC < 2.5V, the comparator’s outputs clear

(CMPOUT pull-down, CMPOUT open) regardless of the

CMP+ pin voltage. The LATCH pin high impedance input

state tolerates ±10μA of leakage current. Bypass this pin

to GND to compensate for high dV/dt on adjacent pins.

Do not exceed 100V on this pin.

I+, I– (Pins 11, 10): Current Sense Inputs. The voltage differ-

ence at these pins represents the current input factor to the

power calculation multiplier and to the current scaler. The

difference may be positive or negative, but both pin voltages

must be at least 4V and no more than 80V above GND,

completely independent of the VCC voltage. Both pins sink

approximately 100μA of bias current in addition to having

an effective 5kΩ shunt between them. The input differential

voltage range is ±200mV. Do not exceed ±36V differ-

entially or 100V on either pin.

VCC (Pin 12): Voltage Supply. The voltage supply operat-

ing range is 6V to 80V. When operating with VCC > 15V,

package heating can be reduced by adding an external

series dropping resistor. Bypass this pin to GND to improve

supply rejection at frequencies above 10kHz as needed.

Do not exceed 100V on this pin.

Exposed Pad (Pin 13 in DFN Package): The exposed pad

may be left open or connected to device ground. For best

thermal performance, the exposed pad must be soldered

to the PCB.

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