LTC6948 datasheet(24/32 Pages) AD

24 / 32 page

LTC5594

Rev A

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APPLICATIONS INFORMATION

Temperature Diode

A schematic of the TEMP pin is shown in Figure 14. The

temperature diode can be used to directly measure the

die temperature. A 40k resistor is recommended to VCC

to generate a 100µA current source for the diode readout.

The temperature slope is about –1.52mV/°C.

Figure 14. Schematic of the TEMP Pin

Figure 15. Simplified Schematic of the EN (or AMPD)

Pin Interface

Enable Interface

A simplified schematic of the EN pin is shown in Figure 15.

TheenablevoltagenecessarytoturnontheLTC5594is0.7

• OVDD. To disable or turn off the chip, this voltage should

bebelow0.3•OVDD.IftheENpinisnotconnected,thechip

is disabled. An internal 200kΩ pull-down keeps the part in

shutdown mode if the pin is left floating. The LTC5594 can

be put into a lower current sleep mode through the serial

interface by writing 0x00 to register 0x16. This will dis-

Table 8. IF Amplifier State vs Logic Levels

EAMP

AMPD Pin

OFF

100

R20

40.2k

LTC5594

GND

VTEMP

TEMP

5594 F14

VCC

200k

LTC5594

GND

5594 F15

VCC

(or AMPD)

able the demodulator, amplifier, DC offset, and nonlinearity

adjust circuits which are controlled by the EDEM, EAMP,

EDC, and EADJ bits. Alternatively, writing any combination

of bits to the four MSB’s of register 0x16 will enable or

disable the individual circuit blocks.

AMPD Interface

Also shown in Figure 15 is the simplified schematic for

the AMPD IF amplifier disable pin. The IF amplifiers are

enabled if the logical AND of AMPD and the EAMP register

is 1. The IF amplifier state is detailed in Table 8.

Digital Input Pins

Figure 16 shows the simplified schematics for the digital

input pins, SCK, CSB, and SDI. These pins should not be

left floating, since there is no internal pull-down or pull-up.

Figure 16. Simplified Schematic of the Digital

Input Pins (SCK, CSB, SDI)

LTC5594

GND

DIGITAL

INPUT

5594 F16

VCC

OVDD Interface

Figure 17 shows the simplified schematic of the OVDD

interface. The OVDD pin supplies the voltage for the digital

inputs and SDO pin. By setting the pin at 1.2V to 3.3V, the

serial port can function with 1.2V to 3.3V logic levels. It is

important that when sequencing the supply voltages for

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