LTC2995
PIN FUNCTIONS
D
+
:
Diode Sense Current Source. D
+
sources the remote
diode sensing current. Connect D
+
to the anode of the re-
mote sensor device. It is recommended to connect a 470pF
bypass capacitor between D
+
and D
–
. Larger capacitors
may cause settling time errors (see Typical Performance
Characteristics). If D
+
is tied to V
CC
, the LTC2995 measures
the internal sensor temperature. Tie D
+
to V
CC
if unused.
D
–
:
Diode Sense Current Sink. Connect D
–
to the cathode
of the remote sensor device. Tie D
–
to GND for single
wire remote temperature measurement (see Applications
Information) or internal temperature sensing.
DS:
Diode Select Input. Three state pin that selects tem-
perature sensor location. Tie DS to V
CC
to monitor the
temperature of the internal diode or to GND to monitor the
temperature of the external diode. When DS is left uncon-
nected, the LTC2995 monitors both sensors alternately.
If D
+
is tied to V
CC
, the LTC2995 measures the internal
sensor temperature regardless of the state of DS.
Exposed Pad:
Exposed pad may be left open or soldered
to GND for better thermal coupling.
GND:
Device Ground
OV:
Overvoltage Logic Output. Open drain logic output
that pulls to GND when either the voltage at VL1 or VL2
is above 0.5V. Held low for a programmable delay time
set by the capacitor connected to pin TMR.
OV
has a weak
400kΩ pull-up to V
CC
and may be pulled above V
CC
using
an external pull-up. Leave
OV
open if unused.
PS:
Polarity Select Input. Selects the polarity of tempera-
ture thresholds VT1 and VT2. Connect PS to V
CC
to config-
ure VT1 as undertemperature and VT2 as overtemperature
threshold. Leave PS unconnected to configure both VT1
and VT2 as overtemperature thresholds. Connect PS to
GND to configure both VT1 and VT2 as undertemperature
thresholds. Tie to V
CC
if temperature thresholds are unused.
TMR:
Reset Delay Timer. Attach an external capacitor
(CTMR) to GND to set the delay time until alerts on
TO1,
TO2, UV
and
OV
are reset. Leaving the pin open generates
a minimum delay of 500μs. Capacitance on this pin adds
an additional 8ms/nF reset delay time. Tie TMR to V
CC
to
bypass the timer.
TO1:
Temperature Logic Output 1. Open drain logic output
that pulls to GND when V
PTAT
crosses the threshold voltage
on pin VT1 with a polarity set by the PS pin (see Table 3
in Applications Information). When V
PTAT
crosses the
threshold voltage on pin VT1 with opposite polarity, an
additional hysteresis of 20mV is required to release
TO1
high after a delay adjustable by the capacitor on TMR.
TO1
has a weak 400kΩ pull-up to V
CC
and may be pulled above
V
CC
using an external pull-up. Leave
TO1
open if unused.
TO2:
Temperature Logic Output 2. Open drain logic output
that pulls to GND when V
PTAT
crosses the threshold voltage
on pin VT2 with a polarity set by the PS pin (see Table 3
in Applications Information). When V
PTAT
crosses the
threshold voltage on pin VT2 with opposite polarity, an
additional hysteresis of 20mV is required to release
TO2
high after a delay adjustable by the capacitor on TMR.
TO2
has a weak 400kΩ pull-up to V
CC
and may be pulled above
V
CC
using an external pull-up. Leave
TO2
open if unused.
UV:
Undervoltage Logic Output. Open drain logic output
that pulls to GND when either the voltage at VH1 or VH2
is below 0.5V. Held low for an adjustable delay time set
by the capacitor connected to pin TMR.
UV
has a weak
400kΩ pull-up to V
CC
and may be pulled above V
CC
using
an external pull-up. Leave pin open if unused.
V
CC
:
Supply Voltage. Bypass this pin to GND with a 0.1μF
(or greater) capacitor. V
CC
operating range is 2.25V to 5.5V.
VH1, VH2:
Voltage High Inputs 1 and 2. When the voltage
on either pin is below 0.5V, an undervoltage condition is
triggered. Tie pin to V
CC
if unused.
VL1, VL2:
Voltage Low Inputs 1 and 2. When the voltage
on either pin is above 0.5V, an overvoltage condition is
triggered. Tie pin to GND if unused.
V
PTAT
:
Proportional to Absolute Temperature Voltage
Output. The voltage on this pin is proportional to the
selected sensor’s absolute temperature. An internal or
external sensor is chosen with the DS pin. V
PTAT
can
drive up to ±200μA of load current and up to 1000pF of
capacitive load. For larger load capacitances insert a 1k
2995f
7
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