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LTC2632

2632fa

BLOCK DIAGRAM

FEATURES DESCRIPTION

Dual 12-/10-/8-Bit SPI

OUT

DACs with

10ppm/°C Reference

The LTC

2632 is a family of dual 12-, 10-, and 8-bit voltage-

output DACs with an integrated, high-accuracy, low-drift

reference in an 8-lead TSOT-23 package. It has rail-to-rail

output buffers and is guaranteed monotonic.

The LTC2632-L has a full-scale output of 2.5V, and operates

from a single 2.7V to 5.5V supply. The LTC2632-H has a

full-scale output of 4.096V, and operates from a 4.5V to

5.5V supply. Each DAC can also operate with an external

reference, which sets the full-scale output to the external

reference voltage.

These DACs communicate via a simple SPI/MICROWIRE

compatible 3-wire serial interface which operates at clock

rates up to 50MHz. The LTC2632 incorporates a power-on

reset circuit. Options are available for reset to zero-scale

or reset to mid-scale in internal reference mode, or reset

to mid-scale in external reference mode after power-up.

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. All other

trademarks are the property of their respective owners. Protected by U.S. Patents including

5396245, 5859606, 6891433, and 6937178.

Integral Nonlinearity (LTC2632A-LZ12)

APPLICATIONS

Integrated Precision Reference

2.5V Full-Scale 10ppm/°C (LTC2632-L)

4.096V Full-Scale 10ppm/°C (LTC2632-H)

Maximum INL Error: ±1LSB (LTC2632A-12)

Low Noise: 0.75mV

P-P

0.1Hz to 200kHz

Guaranteed Monotonic –40°C to 125°C Automotive

Temperature Range

Selectable Internal or External Reference

2.7V to 5.5V Supply Range (LTC2632-L)

Low Power Operation 0.4mA at 3V

Power-On-Reset to Zero-Scale/Mid-Scale

Double-Buffered Data Latches

8-Lead ThinSOT™ Package

Mobile Communications

Process Control and Industrial Automation

Automatic Test Equipment

Portable Equipment

Automotive

CODE

INL (LSB)

–1

–2

1024 3072

2632 TA01

40952048

= 3V

INTERNAL REF.

INTERNAL

REFERENCE

POWER-ON

RESET

32-BIT SHIFT REGISTER

CONTROL

LOGIC

DECODE

SCK

REF

2632 BD

CS/LD

SDI

OUTA

OUTB

DAC A

DAC B

SWITCH

GND

Summary of content (24 pages)

PAGE 1
LTC2632 Dual 12-/10-/8-Bit SPI VOUT DACs with 10ppm/°C Reference DESCRIPTION FEATURES n n n n n n n n n n Integrated Precision Reference 2.5V Full-Scale 10ppm/°C (LTC2632-L) 4.096V Full-Scale 10ppm/°C (LTC2632-H) Maximum INL Error: ±1LSB (LTC2632A-12) Low Noise: 0.75mVP-P 0.1Hz to 200kHz Guaranteed Monotonic –40°C to 125°C Automotive Temperature Range Selectable Internal or External Reference 2.7V to 5.5V Supply Range (LTC2632-L) Low Power Operation 0.
PAGE 2
LTC2632 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Notes 1, 2) TOP VIEW Supply Voltage (VCC).................................... –0.3V to 6V SCK, SDI....................................................... –0.3V to 6V CS/LD (Note 11)................–0.3V to Min (VCC + 0.3V, 6V) VOUTA, VOUTB....................–0.3V to Min (VCC + 0.3V, 6V) REF...................................–0.3V to Min (VCC + 0.3V, 6V) Operating Temperature Range LTC2632C.................................................
PAGE 3
LTC2632 PRODUCT SELECTION GUIDE PART MARKING* VFS WITH INTERNAL REFERENCE LTC2632A-LI12 LTFSJ 2.5V • (4095/4096) Mid-Scale LTC2632A-LX12 LTFSH 2.5V • (4095/4096) Mid-Scale LTC2632A-LZ12 LTFSG 2.5V • (4095/4096) Zero LTC2632A-HI12 LTFSM 4.096V • (4095/4096) LTC2632A-HZ12 LTFSK 4.096V • (4095/4096) LTC2632-LI12 LTFSJ LTC2632-LI10 LTFSQ LTC2632-LI8 LTFSW 2.5V • (255/256) Mid-Scale Internal 8-Bit 2.7V to 5.5V ±0.5LSB LTC2632-LX12 LTFSH 2.
PAGE 4
LTC2632 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 2.7V to 5.5V, VOUT unloaded unless otherwise specified. LTC2632-LI12/-LI10/-LI8/-LX12/-LX10/-LX8/-LZ12/-LZ10/-LZ8, LTC2632A-LI12/-LX12/-LZ12 (VFS = 2.
PAGE 5
LTC2632 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 2.7V to 5.5V, VOUT unloaded unless otherwise specified. LTC2632-LI12/-LI10/-LI8/-LX12/-LX10/-LX8/-LZ12/-LZ10/-LZ8, LTC2632A-LI12/-LX12/-LZ12 (VFS = 2.5V) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VCC V 200 kΩ 0.005 5.0 µA 1.25 1.
PAGE 6
LTC2632 TIMING CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 2.7V to 5.5V, VOUT unloaded unless otherwise specified. LTC2632-LI12/-LI10/-LI8/-LX12/-LX10/-LX8/-LZ12/-LZ10/-LZ8, LTC2632A-LI12/-LX12/-LZ12 (VFS = 2.
PAGE 7
LTC2632 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 4.5V to 5.5V, VOUT unloaded unless otherwise specified. LTC2632-HI12/-HI10/-HI8/-HZ12/-HZ10/-HZ8, LTC2632A-HI12/-HZ12 (VFS = 4.096V) SYMBOL PARAMETER LTC2632-8 LTC2632-10 LTC2632-12 LTC2632A-12 MIN TYP MAX MIN TYP MAX MIN TYP MAX MIN TYP MAX CONDITIONS UNITS DC Performance Resolution l 8 8 10 Monotonicity VCC = 5V, Internal Ref.
PAGE 8
LTC2632 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 4.5V to 5.5V, VOUT unloaded unless otherwise specified. LTC2632-HI12/-HI10/-HI8/-HZ12/-HZ10/-HZ8, LTC2632A-HI12/-HZ12 (VFS = 4.096V) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VCC V 160 200 kΩ 0.005 5.0 µA 2.048 2.
PAGE 9
LTC2632 TIMING CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 4.5V to 5.5V, VOUT unloaded unless otherwise specified. LTC2632-HI12/-HI10/-HI8/-HZ12/-HZ10/-HZ8, LTC2632A-HI12/-HZ12 (VFS = 4.
PAGE 10
LTC2632 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. LTC2632-L12 (Internal Reference, VFS = 2.5V) Integral Nonlinearity (INL) 1.0 Differential Nonlinearity (DNL) 1.0 VCC = 3V 0.5 DNL (LSB) INL (LSB) 0.5 0 0 –0.5 –0.5 –1.0 VCC = 3V 1024 0 2048 CODE 3072 –1.0 4095 0 1024 3072 2048 CODE 4095 2632 G02 2632 G01 INL vs Temperature 1.0 VCC = 3V INL (POS) 0 –0.5 –1.0 –50 –25 INL (NEG) 0 DNL (POS) 0 DNL (NEG) –1.
PAGE 11
LTC2632 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. LTC2632-H12 (Internal Reference, VFS = 4.096V) Integral Nonlinearity (INL) 1.0 Differential Nonlinearity (DNL) 1.0 VCC = 5V 0.5 DNL (LSB) INL (LSB) 0.5 0 0 –0.5 –0.5 –1.0 VCC = 5V 1024 0 2048 CODE 3072 –1.0 4095 0 1024 3072 2048 CODE 4095 2632 G09 2632 G08 INL vs Temperature 1.0 VCC = 5V INL (POS) 0.5 0 INL (NEG) 0 25 50 75 100 125 150 TEMPERATURE (°C) DNL (POS) 0 DNL (NEG) –1.
PAGE 12
LTC2632 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. LTC2632-10 Integral Nonlinearity (INL) 1.0 Differential Nonlinearity (DNL) 1.0 VCC = 3V VFS = 2.5V INTERNAL REF 0.5 DNL (LSB) INL (LSB) 0.5 0 –0.5 –1.0 VCC = 3V VFS = 2.5V INTERNAL REF 0 –0.5 256 0 512 CODE 768 –1.0 1023 256 0 512 CODE 768 1023 2632 G15 2632 G16 LTC2632-8 Integral Nonlinearity (INL) 0.50 Differential Nonlinearity (DNL) 0.50 VCC = 3V VFS = 2.5V INTERNAL REF 0.
PAGE 13
LTC2632 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. LTC2632 Large-Signal Response Mid-Scale Glitch Impulse Power-On Reset Glitch LTC2632-L CS/LD 5V/DIV VCC 2V/DIV VOUT 0.5V/DIV LTC2632-H12, VCC = 5V 3.0nV-s TYP VOUT 2mV/DIV LTC2632-L12, VCC = 3V 2.8nV-s TYP VFS = VCC = 5V 1/4 SCALE to 3/4 SCALE 2µs/DIV 2632 G23 2µs/DIV 2632 G22 Headroom at Rails vs Output Current 2632 G24 LTC2632-H 5V SOURCING 4.0 VCC = 5V INTERNAL REF CS/LD 5V/DIV 3.
PAGE 14
LTC2632 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. LTC2632 Multiplying Bandwidth Noise Voltage vs Frequency 500 2 0 NOISE VOLTAGE (nV/√Hz) –2 –4 dB –6 –8 –10 –12 VCC = 5V VREF(DC) = 2V VREF(AC) = 0.2VP-P CODE = FULL-SCALE –14 –16 –18 1k 10k 100k FREQUENCY (Hz) 400 VCC = 5V CODE = MID-SCALE INTERNAL REFERENCE 300 LTC2632-H 200 LTC2632-L 100 0 100 1M 1k 100k 10k FREQUENCY (Hz) 2632 G30 2632 G29 Gain Error vs Reference Input 0.8 GAIN ERROR (%FSR) 0.
PAGE 15
LTC2632 PIN FUNCTIONS SCK (Pin 1): Serial Interface Clock Input. CMOS and TTL compatible. GND (Pin 4): Ground. CS/LD (Pin 2): Serial Interface Chip Select/Load Input. When CS/LD is low, SCK is enabled for shifting data on SDI into the register. When CS/LD is taken high, SCK is disabled and the specified command (see Table 1) is executed. VCC (Pin 7): Supply Voltage Input. 2.7V ≤ VCC ≤ 5.5V (LTC2632-L) or 4.5V ≤ VCC ≤ 5.5V (LTC2632-H). Bypass to GND with a 0.1µF capacitor.
PAGE 16
LTC2632 BLOCK DIAGRAM INTERNAL REFERENCE GND SWITCH VREF CS/LD REGISTER REGISTER DAC A REGISTER REGISTER VCC VOUTA REF DAC B VOUTB SDI CONTROL LOGIC DECODE SCK POWER-ON RESET 32-BIT SHIFT REGISTER 2632 BD TIMING DIAGRAM t1 t2 SCK t3 1 2 t6 t4 3 23 24 t10 SDI t5 t7 CS/LD 2632 F01 Figure 1.
PAGE 17
LTC2632 OPERATION The LTC2632 is a family of dual voltage output DACs in an 8-lead TSOT package. Each DAC can operate rail-to-rail using an external reference, or with its full-scale voltage set by an integrated reference. Fifteen combinations of accuracy (12-, 10-, and 8-bit), power-on reset value (zeroscale, mid-scale in internal reference mode, or mid-scale in external reference mode), and full-scale voltage (2.5V or 4.096V) are available.
PAGE 18
LTC2632 OPERATION INPUT WORD (LTC2632-12) COMMAND C3 C2 C1 ADDRESS C0 A3 A2 A1 DATA (12 BITS + 4 DON’T-CARE BITS) A0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 MSB D0 X X X X X X X X X X X X X X LSB INPUT WORD (LTC2632-10) COMMAND C3 C2 C1 ADDRESS C0 A3 A2 A1 DATA (10 BITS + 6 DON’T-CARE BITS) A0 D9 D8 D7 D6 D5 D4 D3 D2 D1 MSB D0 X LSB INPUT WORD (LTC2632-8) COMMAND C3 C2 C1 ADDRESS C0 A3 A2 A1 DATA (8 BITS + 8 DON’T-CARE BITS) A0 D7 D6 D5 D4 MSB
PAGE 19
LTC2632 OPERATION Reference Modes Power-Down Mode For applications where an accurate external reference is not available, nor desirable due to limited space, the LTC2632 has a user-selectable, integrated reference. The integrated reference voltage is internally amplified by 2x to provide the full-scale DAC output voltage range. The LTC2632-LI/ LTC2632-LX/LTC2632-LZ provides a full-scale output of 2.5V. The LTC2632-HI/LTC2632-HZ provides a full-scale output of 4.096V.
PAGE 20
LTC2632 OPERATION Voltage Output Board Layout The LTC2632’s integrated rail-to-rail amplifier has guaranteed load regulation when sourcing or sinking up to 10mA at 5V, and 5mA at 3V. The PC board should have separate areas for the analog and digital sections of the circuit. A single, solid ground plane should be used, with analog and digital signals carefully routed over separate areas of the plane.
PAGE 21
2 X 1 X SCK SDI CS/LD 4 X X 5 6 X 8 DON’T CARE BITS X 3 C2 C3 SDI C1 3 X 7 4 X 8 C0 COMMAND WORD 2 1 SCK CS/LD A1 7 ADDRESS A2 6 A0 8 D11 9 D10 10 D9 D8 12 D7 13 D6 14 24-BIT INPUT WORD 11 D5 15 D3 17 DATA WORD D4 16 D2 18 D1 19 D0 20 C2 C3 C1 11 12 C0 A3 13 A1 15 A0 16 D11 17 D10 18 32-BIT INPUT WORD ADDRESS A2 14 D9 19 D8 20 D7 21 D6 22 D5 23 24 D3 25 X 21 DATA WORD D4 Figure 3b.
PAGE 22
LTC2632 OPERATION VREF = VCC POSITIVE FSE VREF = VCC OUTPUT VOLTAGE OUTPUT VOLTAGE INPUT CODE (c) OUTPUT VOLTAGE 0V NEGATIVE OFFSET 0 2,048 INPUT CODE (a) 0V 2632 F04 4,095 INPUT CODE (b) Figure 4.
PAGE 23
LTC2632 REVISION HISTORY REV DATE DESCRIPTION PAGE NUMBER A 3/11 Revised part numbering 2 to 9, 17, 19, 24 2632fa Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
PAGE 24
LTC2632 TYPICAL APPLICATION LTC2632 DACs Adjust LTC2755-16 Offset, Amplified with LT1991 PGA to ±5V 5V 15V VDD 0.1µF LTC2755 ROFSA 0.1µF 15V 30pF RIN1 RFBA + IOUT1A 1/2 LT1469 RCOM1 – 0.1µF DAC A 0.1µF – IOUT2A RVOSA 5V 30pF –15V –15V LT1634-1.25 REFA OUTA 1/2 LT1469 + 0.1µF – + DAC B DAC D LT6240 0.1µF 30k 10V 5V –15V DAC C 0.1µF REF GND VCC LTC2632TS8-LI12 DAC A 0.1µF 0.