LTC2990
23
2990fe
For more information www.linear.com/LTC2990
Typical applicaTions
Liquid-Level Indicator
V
CC
LTC2990
3.3V
µC
GND
SDA
SCL
ADR0
ADR1
V1
V4
V3
V2
470pF
3.3V
470pF
T
INTERNAL
CONTROL REGISTER: 0x5D
T
AMB
REG 4, 5 0.0625°C/LSB
T
HI
REG 6, 7 0.0625°C/LSB
T
LO
REG A, B 0.0625°C/LSB
V
CC
REG E, F 2.5V + 305.18µV/LSB
NDS351AN
2290 TA09
HEATER: 75Ω 0.125W
*SENSOR MMBT3904, DIODE CONNECTED
SENSOR LO*
∆T = ~2.0°C pp, SENSOR HI
~0.2°C pp, SENSOR LO
SENSOR HI*
HEATER ENABLE
2 SECOND PULSE
HEATER ENABLE
SENSOR HI
SENSOR LO
0.1µF
Oscillator/Reference Oven Temperature Regulation
V
CC
V1
LTC2990
HEATER
PWR
=
I •V
0.1Ω
HEATER
VOLTAGE
2-WIRE
I
2
C
INTERFACE
5V
GND
470pF
FEED
FORWARD
FEED
BACK
HEATER
HEATER CONSTRUCTION:
5FT COIL OF #34 ENAMEL WIRE
~1.6Ω AT 70°C
P
HEATER
= ~0.4W WITH T
A
= 20°C
HEATER POWER = α • (T
SET
– T
AMB
) + β • ∫(T
OVEN
– T
SET
) dt
20°C
AMBIENT
STYROFOAM
INSULATION
70°C
OVEN
T
OVEN
α = 0.004W, β = 0.00005W/DEG-s
MMBT3904
SDA
SCL
ADR0
ADR1
V3
V4
V2
2990 TA10
T
INTERNAL
CURRENT AND TEMPERATURE CONFIGURATION:
CONTROL REGISTER: 0x59
T
AMB
REG 4, 5 0.0625°C/LSB
I
HEATER
REG 6, 7 269µVLSB
T
HEATER
REG A, B 0.0625°C/LSB
V
CC
REG E, F 2.5V + 305.18µV/LSB
VOLTAGE AND TEMPERATURE CONFIGURATION:
CONTROL REGISTER: 0x58
T
AMB
REG 4, 5 0.0625°C/LSB
V1, V2 REG 8, 9 305.18µVLSB
T
OVEN
REG A, B 0.0625°C/LSB
V
CC
REG E, F 2.5V + 305.18µV/LSB
0.1µF
