lt2940 Linear Technology Corporation, lt2940 Datasheet - Page 8

• Manufacturer Part Number: lt2940
• Description: Power And Current Monitor
• Manufacturer: Linear Technology Corporation

PIN FUNCTIONS
LT2940
CMPOUT (Pin 1): Inverting Open-Collector Comparator
Output. When the LATCH pin’s state does not override the
comparator, CMPOUT pulls low when CMP
pull-down shuts off when CMP
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
V
shuts off when CMP
to 36V maximum. Do not sink more than 22mA DC.
CMP
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 ±0.4V
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 V
Tie IMON to GND if unused.
GND (Pin 6): Device Ground.
8
CC
< 2.5V, or when the LATCH pin is low. The pull-down
+
(Pin 3): Positive Comparator Input. The integrated
2
. Do not exceed V
+
> 1.24V. CMPOUT may be pulled up
CC
CC
+ 1V, up to 16V maximum.
+ 1V, up to 16V maximum.
+
< 1.21V, or V
+
+
> 1.24V. The
CC
< 1.21V, or
< 2.5V or
+
V
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 V
(CMPOUT pull-down, CMPOUT open) regardless of the
CMP
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
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 V
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.
V
ing range is 6V to 80V. When operating with V
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.
+
+
CC
, I
, V
–
(Pin 12): Voltage Supply. The voltage supply operat-
(Pins 11, 10): Current Sense Inputs. The voltage differ-
+
–
pin voltage. The LATCH pin high impedance input
(Pins 8, 7): Voltage Sense Inputs. The voltage
CC
< 2.5V, the comparator’s outputs clear
CC
voltage. Both pins sink
CC
> 15V,
2940f
+