DS1870(2004) Просмотр технического описания (PDF) - Maxim Integrated

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DS1870
(Rev.:2004)

LDMOS RF Power-Amplifier Bias Controller

Maxim Integrated 

LDMOS RF Power-Amplifier Bias

Controller

Table 3. Internal Temperature-Monitor

Factory Default Calibration

SIGNAL

Temp

+FS

SIGNAL

+127.97°C

+FS

(hex)

7FF8

-FS

SIGNAL

-128.00°C

-FS

(hex)

8000

Temperature-Monitor Operation

The internal temperature monitor values are stored as

16-bit 2’s complement numbers at memory addresses

60h to 61h. The round-robin update time (tframe) for the

temperature register is the same as the voltage moni-

tors. The factory default calibration values for the tem-

perature monitor are shown in Table 3.

To convert the 2’s complement register value to the

temperature it represents, first convert the 2-byte hexa-

decimal value to a decimal value as if it is an unsigned

value, then divide the result by 256. Finally, subtract

256 if the result of the division is greater than or equal

to +128. Table 4 shows example converted values.

The offset of the temperature sensor can be adjusted

using the internal calibration registers to account for

differences between the ambient temperature at the

location of the DS1870 and the temperature of the

device it is biasing. When offsets are applied to the

temperature measurement, the value converted will be

off by a fixed value from the DS1870’s ambient temper-

ature. For more information, see the Temperature

Monitor Offset Calibration section.

Potentiometer Operation

Both of the DS1870’s potentiometers are 256 positions

with their high terminals connected to the high common

pin, HCOM. The low terminals of the potentiometers are

internally shunted to GND by resistors such that the

output voltage is 3V to 5V when HCOM is connected to

a 5V source. The internal shunt resistors and the poten-

tiometer’s end-to-end resistance feature matching tem-

perature coefficients that prevent the output voltage

from drifting over temperature.

External resistors can be placed from HCOM to LX and/or

from LX to GND to modify the typical output voltage.

Normal Operation

During normal operation, each potentiometer’s position

is automatically adjusted to the sum of its temperature

and drain LUT values after each round of conversions.

The potentiometer setting is applied after both the base

and offset LUT values are recalled from memory. The

sum of the currently indexed values in the POT1 Temp

LUT (memory table 2) and the POT1 Drain LUT (memo-

ry table 4) control potentiometer 1. The sum of the cur-

rently indexed values in the POT2 Temp LUT (memory

Table 4. Temperature Conversion Values

MSB

(bin)

01000000

01000000

01011111

11110110

11011000

LSB

(bin)

00000000

00001111

00000000

00000000

00000000

TEMPERATURE

(°C)

+64

+64.059

+95

-10

-40

Table 5. LUT Addresses for

Corresponding Temperature Values

LUT ADDRESS (hex)

80

81

82

…

C6

C7

CORRESPONDING

TEMPERATURE (°C)

≤ -40°C

-38°C

-36°C

…

+100°C

≥ +102°C

table 3) and the POT2 Drain LUT (memory table 5) con-

trol potentiometer 2. In the event that two table values

are summed and the result is greater than 255 or less

than 0, the potentiometer’s position is set to 255 or 0,

respectively.

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