LXE1810
L I N F I N I T Y
Thermo Electric Cooler Drive
D I V I S I O N
NO
T R OB
EC SO
OM L
ME ET
ND E P
ED
R
FO OD
R
NE UC
W T
DE
SIG
NS
KEY FEATURES
• Input Voltage +7 to +12 Volts Max.
• Adjust R4 for Temperature setting
• Output current is 1.5A Maximum.
• Assy # EVB2805
• Change the resistance value of R8 to set the maximum
output voltage limit. Use a dummy load of 20 to 50 ohms
while making this change. A smaller resistance value
increase the output voltage minimum value is 15k ohms.
• Thermister Input is not polarity sensitive for RT-1 and RT-2,
connect so wires do not cross.
• If the set temperature is lower than the room temperature
when power is applied; the output drive will put a positive
potential across the Thermo electric cooler.
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DESCRIPTION
IMPORTANT: For the most current data, consult MICROSEMI’s website:
http://www.microsemi.com/
BOTTOM
TOP
R2
R4
C4
R1
C5
C2
R7
C7
C1
U2
R3
R11
U1
C8
R9
R8
R6
C6
R12 R10
C9
R5
C10
R13
Q2
C12
Q1
L2
C11
GND
L1
C3
+12V
TEC+ RT-1 RT-2
C13
C14
TEC-
LXE1810
TEC
Copyright  2000
Rev. 0.4, 2002-10-31
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
LXE1810
L I N F I N I T Y
Thermo Electric Cooler Drive
D I V I S I O N
NO
T R OB
EC SO
OM L
ME ET
ND E P
ED
R
FO OD
R
NE UC
W T
DE
SIG
NS
The LX1810 has an internal 5V reference at PIN 1. This
reference is used with the POT adjustment that is the
temperature setting and with the thermister resister divider
that is the temperature feedback. The value of R3 is set
equal to the value of the thermister at the temperature of
operation, (±20%).
The values for R5, R6, R7, C6, & C7 are used to set the
loop compensation for stable closed loop operation. This
Eval board has been compensated for a Marlow Industries
Inc. MI1012T-01, TEC device.
The value of R8 sets the peak output voltage limit of the
power amplifier. The value shown sets the limit to 4 volts
maximum. This is the method used to set the maximum
current through the TEC device. With a TEC resistance of
3 ohms the maximum current will be 1.3 amps. The
LX1810 has an internal cycle by cycle current limit that is
activated after a count of 9 cycles of over current. When
activated the LX1810 goes into a hiccup mode until it has 2
cycles of normal current. This mode will prevent damage
when the output has a short circuit.
The inductors, L1 and L2 are selected for the continuous
current rating required by the device being driven by the
power amplifier. At the 400kHz switching frequency an
inductance value between 10µH and 20µH should be used.
Now you can find the smallest package at the desired price.
C13 and C14 provide an LC low pass filter. The TEC
devices have a slow rate of change of temperature with time,
which means the loop bandwidth will probably be under
100Hz. This means that the LC filters can be set in the range
of 10kHz. Therefore, you can use the largest cap value with
the voltage and package size required by your design.
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APPLICATION NOTE
The LX1810 has internal FET drivers capable of driving
the highest power SO-8 package MOSFETs. An example of
these devices are the Fairchild FDS6875 Dual P-Channel
MOSFET, capable of 6 amps and the FDS6890A Dual NChannel MOSFET, capable of 8 amps. With these devices
and the proper inductors, and the correct amount of heat
sink, the power amplifier is capable of 5 amps continuous at
an output voltage of 12 volts. So, any output power design is
feasible up to this maximum design with the proper selection
of components.
APPLICATION
+12V
TEC - TEC-
LX1810
GND
RT-2
N/U
ISI
CP
VDD
PVDD
P+
N+
NPPGND
CN
FB INFB IN+
FB OUT
TEC +TEC+
APPLICATION
RT-1
1
GND
N/C
2.5VREF
RPWM
CPWM
N/U
N/U
N/U
SLEEP
N/U
N/U
EA IN
EA OUT
Figure 1 – Application Schematic
Copyright  2000
Rev. 0.4, 2002-10-31
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2