DS3501U+ Datasheet DS3501U+, DS3501U+H | P7-P9

DS3501

High-Voltage, NV, I

C POT with Temp Sensor

and Lookup Table

_____________________________________________________________________ 7

Detailed Description

The DS3501 operates in one of three operating modes:

Default Mode, LUT Mode, or LUT Adder Mode. In

Default Mode, the DS3501 is pin and software compati-

ble with the ISL95311. The potentiometer’s wiper posi-

tion is controlled by the Wiper Register (WR) and the

NV Initial Value Register (IVR) via the I

C interface. In

LUT Mode and LUT Adder Mode, the potentiometer’s

wiper position is calculated/controlled as a function of

the current temperature measured by the DS3501’s

internal temperature sensor. The difference between

the two LUT modes is the way the potentiometer wiper

position is calculated. A detailed description of the

three modes as well as additional features of the

DS3501 follow below.

Digital Potentiometer Output

The potentiometer consists of 127 resistors in series

connected between the RH and RL pins. Between each

resistance and at the two end points, RH and RL, solid-

state switches enable RW to be connected within the

resistive network. The wiper position and the output on

RW are decoded based on the value in WR. If RH, RL,

and RW are externally connected in a voltage-divider

configuration, then the voltage on RW can be easily

calculated using the following equation:

where WR is the wiper position in decimal (0–127).

Temperature Conversion and

Supply Voltage Monitoring

Temperature Conversion

The DS3501 features an internal 8-bit temperature sen-

sor that is capable of driving the LUT and providing a

measurement of the ambient temperature over I

C by

reading address 0Ch. The sensor is functional over the

entire operating temperature range and is in signed

two’s complement format with a resolution of 1°C/bit.

See below for the temperature sensor’s bit weights.

To calculate the temperature, treat the two’s comple-

ment binary value as an unsigned binary number, then

convert it to decimal. If the result is greater than or

equal to 128, subtract 256 from the result.

Supply Voltage Monitoring

The DS3501 also features an internal 8-bit supply volt-

age (V

) monitor. A value of the supply voltage mea-

surement can be read over I

C at the address 0Eh.

To calculate the supply voltage, simply convert the

hexadecimal result into decimal and then multiply it by

the LSB as shown in the

Analog Voltage Monitoring

Characteristics

electrical table.

Mode Selection

The DS3501 mode of operation is determined by two

bits located in Control Register 1 (CR1), which is non-

volatile. In particular, the mode is determined by the

Update Mode bit (CR1.0) and the Adder Mode bit

(CR1.1). Table 1 illustrates how the two control bits are

used to select the operating mode. When shipped from

the factory, the DS3501 is programmed with the CR1.0

bit = 0, hence configuring the DS3501 in Default Mode.

Default Mode

Default Mode of the DS3501 is the simplest mode of the

three. As shown in the Default Mode Block Diagram,

the potentiometer is controlled by the Wiper Register/

Initial Value Register (WR/IVR). Upon power-up of the

DS3501, the value stored in the NV Initial Value

time after by writing the desired value to the WR/IVR

address 00h and is implemented as EEPROM shad-

owed SRAM. This register can be visualized as an

SRAM byte (the WR portion) in parallel with a EEPROM

byte (the IVR portion). The operation of the register is

controlled by the Shadow EEPROM (SEE) bit, CR0.7.

When the SEE bit = 0 (default), data written to memory

address 00h by I

C actually gets stored in both SRAM

(WR) and EEPROM (IVR). Conversely, when SEE = 1,

only the SRAM (WR) is written to the new value. The

EEPROM byte (IVR) continues to store the last value

written to it when SEE was 0. Reading memory address

00h reads the value stored in WR. As shown in the

Default Mode memory map (see Table 2), the SEE bit is

volatile and its power-up default state is 0.

RW RL RH RL

=+ −

()

127

UPDATE MODE

BIT (CR1.0)

ADDER MODE

BIT (CR1.1)

MODE

0 X Default Mode (default)

1 0 LUT Mode

1 1 LUT Adder Mode

Table 1. DS3501 Operating Modes

DS3501

High-Voltage, NV, I

C POT with Temp Sensor

and Lookup Table

8 _____________________________________________________________________

LUT Mode

LUT Mode is selected by setting the Update Mode bit

(CR1.0) to 1 and the Adder Mode bit (CR1.1) to 0. An

overview of the DS3501 in this mode is illustrated in the

LUT Mode and LUT Adder Mode Block Diagram. Also,

the memory map for LUT Mode and LUT Adder Mode is

shown in Table 3. The major difference between the two

LUT modes is whether or not the value in the IVR is

added to the values stored in the lookup table. The

dashed line/arrow shown in the block diagram is not

active in LUT mode.

When in LUT Mode, on power-up the IVR value is

recalled into the WR register. This value will remain

there until completion of the first temperature conver-

sion following power-up. The temperature is measured

every t

FRAME

. The temperature value is used to calcu-

late an index that points to the corresponding value in

the lookup table. This index is referred to as the LUT

Address Register (LUTAR). The value stored in the LUT

at the location pointed to by LUTAR is called LUTVAL.

The Wiper Register is then automatically loaded with

LUTVAL. The process then repeats itself, continuously

updating the wiper setting in a closed-loop fashion.

In this mode the 36-byte LUT is populated with wiper

settings for each four-degree temperature window.

Valid wiper settings are 00h to 7Fh. The memory map in

Table 3 shows the memory address of the LUT as well

as the corresponding temperature range for each byte

in the LUT. Also, the LUT features one-degree hystere-

sis to prevent chattering if the measured temperature

ADDRESS

(HEX)

VOLATILE/NONVOLATILE

FACTORY/POWER-UP

DEFAULT

WR/IVR

Wiper Register/Initial Value

00h* NV (Shadowed) 40h

CR0 Control Register 0 02h V 00h

CR1 Control Register 1 03h NV (Shadowed) 00h

CR2 Control Register 2 0Ah V 00h

Table 2. Default Mode Memory Map

In Default Mode, both WR and IVR are accessed through memory location 00h. Refer to the Default Mode section for additional information.

ADDRESS

(HEX)

VOLATILE/NONVOLATILE

FACTORY/POWER-UP

DEFAULT

IVR Initial Value Register 00h* NV (Shadowed) 40h

CR0 Control Register 0 02h V 00h

CR1 Control Register 1 03h NV (Shadowed) 00h

LUTAR LUT Address Register 08h V N/A

WR Wiper Register 09h* V N/A

CR2 Control Register 2 0Ah V 00h

TEMP Temperature Value 0Ch V (Read-Only) N/A

VCC V

Voltage Value 0Eh V (Read-Only) N/A

LUT0 Wiper Value for T ≤ -37°C 80h NV 00h

LUT1 Wiper Value for -36°C to -33°C 81h NV 00h

LUT2 Wiper Value for -32°C to -29°C 82h NV 00h

———— —

LUT33 Wiper Value for +92°C to +95°C A1h NV 00h

LUT34 Wiper Value for +96°C to +99°C A2h NV 00h

LUT35 Wiper Value for T ≥ 100°C A3h NV 00h

Table 3. LUT Mode and LUT Adder Mode Memory Map

In LUT Mode and LUT Adder Mode, the WR is accessed through memory address 09h, while IVR remains at memory address 00h.

DS3501

High-Voltage, NV, I

C POT with Temp Sensor

and Lookup Table

_____________________________________________________________________ 9

falls on the boundary between two windows. As the

temperature increases, the LUT changes on even tem-

perature values (see Figure 1). Conversely, the LUT

changes on odd temperature values when the tempera-

ture is decreasing.

LUT Adder Mode

LUT Adder Mode is selected by setting the Update

Mode bit (CR1.0) to 1 and the Adder Mode bit (CR1.1)

to 1. This mode operates similar to LUT Mode with one

major difference (see the LUT Mode and LUT Adder

Mode Block Diagram). The Wiper Register is loaded

with the sum of LUTVAL and IVR. Furthermore, in this

mode, the values programmed into the LUT are signed

two’s complement. This allows convenient positive or

negative offsetting of the nominal IVR value.

MEMORY LOCATION

LUT20

LUT19

LUT18

LUT17

LUT16

24 28 32 36 40 44

INCREASING

TEMPERATURE

TEMPERATURE (°C)

1°C HYSTERESIS

WINDOW

DECREASING

TEMPERATURE

Figure 1. LUT Hysteresis

Control Register 1 (CR1)

FACTORY DEFAULT 00h

MEMORY TYPE Shadowed Nonvolatile

03h

Reserved Reserved Reserved Reserved Reserved Reserved

Adder

Mode

Update

Mode

bit7 bit0

bit7:2 Reserved

bit1

Adder Mode: This bit is valid only if the Update Mode bit = 1.

0 = Sets the DS3501 to LUT Mode.

1 = Sets the DS3501 to LUT Adder Mode.

bit0

Update Mode:

0 = Sets the DS3501 to Default Mode. In this mode the DS3501 is compatible with the ISL95311 (default).

1 = Sets the DS3501 to one of the two LUT-based modes depending on the Adder Mode bit.

Control Register 0 (CR0)

POWER-UP DEFAULT 00h

MEMORY TYPE Volatile

02h

SEE

Reserved Reserved Reserved Reserved Reserved Reserved Reserved

bit7 bit0

bit7

SEE: Controls functionality of shadowed NV registers (such as the WR/IVR register).

0 = Data written to shadowed NV memory is stored in both SRAM and EEPROM (default).

1 = Data written to shadowed NV memory is stored only in SRAM.

bit6:0 Reserved

DS3501 Control Registers

The DS3501 contains three control registers (CR0, CR1, and CR2) used to configure and control modes and features.

P1-P3 P4-P6 P7-P9 P10-P12 P13-P14

DS3501U+

Mfr. #:

Buy DS3501U+

Manufacturer:

Maxim Integrated

Description:

Digital Potentiometer ICs High-Voltage NV I2C w/Temp Sensor & LUT

Lifecycle:

New from this manufacturer.

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DS3501U+

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