MAX1968EUI datasheet(12/16 Pages) MAXIM

12 / 16 page

MAX1968/MAX1969

Power Drivers for Peltier TEC Modules

Maxim Integrated | 12

www.maximintegrated.com

Setting Voltage and Current Limits

Certain TEC parameters must be considered to guaran-

tee a robust design. These include maximum positive

current, maximum negative current, and the maximum

voltage allowed across the TEC. These limits should be

used to set the MAXIP, MAXIN, and MAXV voltages.

Setting Max Positive and

Negative TEC Current

MAXIP and MAXIN set the maximum positive and nega-

tive TEC currents, respectively. The default current limit

±150mV / RSENSE when MAXIP and MAXIN are con-

nected to REF. To set maximum limits other than the

defaults, connect a resistor-divider from REF to GND to

set VMAXI_. Use resistors in the 10k

Ω to 100kΩ range.

VMAXI_ is related to ITEC by the following equations:

VMAXIP = 10(ITECP(MAX) x RSENSE)

VMAXIN = 10(ITECN(MAX) x RSENSE)

where ITECP(MAX) is the maximum positive TEC current

and ITECN(MAX) is the negative maximum TEC current.

Positive TEC current occurs when CS is less than OS1:

ITEC x RSENSE = VOS1 -VCS

when ITEC > 0.

ITEC x RSENSE = VCS -VOS1

when ITEC < 0.

The MAX1969 controls the TEC current in one direction

(unipolar current flow from OS1 to CS). Set the maxi-

mum unipolar TEC current by applying a voltage to

MAXIN. Connect MAXIP to MAXIN. The equation for

setting MAXIN is the same for the MAX1968 and

MAX1969.

Take care not to exceed the positive or negative cur-

rent limit on the TEC. Refer to the manufacturer’s data

sheet for these limits.

Setting MAX TEC Voltage

Apply a voltage to the MAXV pin to control the maxi-

mum differential TEC voltage. MAXV can vary from 0 to

REF. The voltage across the TEC is four times VMAXV

and can be positive or negative:

|VOS1 - VOS2| = 4 x VMAXV

Set VMAXV with a resistor-divider between REF and

GND using resistors from 10k

Ω to 100kΩ. VMAXV can

vary from 0 to REF.

Control Inputs/Outputs

Output Current Control

The voltage at CTLI directly sets the TEC current. CTLI

is typically driven from the output of a temperature con-

trol loop. For the purposes of the following equations, it

is assumed that positive TEC current is cooling (see

Figure 1). The transfer function relating current through

the TEC (ITEC) and VCTLI is given by:

ITEC = (VCTLI - VREF)/(10 x RSENSE)

where VREF is 1.50V and:

ITEC = (VOS1 - VCS)/RSENSE

CTLI is centered around REF (1.50V). ITEC is zero when

CTLI = 1.50V. When VCTLI > 1.50V the MAX1968 is

cooling. Current flow is from OS2 to OS1. The voltages

on the pins relate as follows:

VOS2 > VOS1 > VCS

The opposite applies when heating. When VCTLI <

1.50V current flows from OS1 to OS2:

VOS2 < VOS1 < VCS

Shutdown Control

The MAX1968/MAX1969 can be placed in a power-sav-

ing shutdown mode by driving

SHDN low. When the

MAX1968/MAX1969 are shut down, the TEC is off (OS1

and OS2 decay to GND) and supply current is reduced

to 2mA (typ).

ITEC Output

ITEC is a status output that provides a voltage proportion-

al to the actual TEC current. ITEC = REF when TEC cur-

rent is zero. The transfer function for the ITEC output is:

VITEC = 1.50 + 8 x (VOS1 - VCS)

Use ITEC to monitor the cooling or heating current

through the TEC. The maximum capacitance that ITEC

can drive is 100pF.

MAX1968EUI Datasheet(PDF) 12 Page - Maxim Integrated Products

MAX1968EUI Datasheet(HTML) 12 Page - Maxim Integrated Products

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Datasheet Download

Link URL