Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsLinear ICsLTC6904CMS8#PBF

LTC6903/LTC6904

69034fe

Typical applicaTion

FeaTures

applicaTions

DescripTion

1kHz to 68MHz Serial

Port Programmable Oscillator

The LTC

6903/LTC6904 are low power self contained digital

frequency sources providing a precision frequency from

1kHz to 68MHz, set through a serial port. The LTC6903/

LTC6904 require no external components other than a

power supply bypass capacitor, and they operate over a

single wide supply range of 2.7V to 5.5V.

The LTC6903/LTC6904 feature a proprietary feedback loop

that linearizes the relationship between digital control set-

ting and frequency, resulting in a very simple frequency

setting equation:

DAC

kHzf MHz

OCT













<<2

2078

1024

8•

()

–

;

where OCT is a 4-bit digital code and DAC is a 10-bit

digital code.

The LTC6903 is controlled by a convenient SPI compatible

serial interface. The LTC6904 uses an industry standard

C compatible interface.

A Microcontroller Controlling Its Clock

Precision Digitally Controlled Oscillator

Power Management

Direct Digital Frequency Synthesis (DDS)

Replacement

Replacement for DAC and VCO

Switched Capacitor Filter Clock

1kHz to 68MHz Square Wave Output

0.5% (Typ) Initial Frequency Accuracy

Frequency Error <1.1% Over All Settings

10ppm/°C Typical Frequency Drift Over

Temperature

0.1% Resolution

1.7mA Typical Supply Current (f < 1MHz, V

= 2.7V)

2.7V to 5.5V Single- Supply Operation

Jitter <0.4% Typical 1kHz to 8MHz

Easy to Use SPI (LTC6903) or I

C (LTC6904) Serial

Interface

Output Enable Pin

–55°C to 125°C Operation

MS8 Package

PIC16F73

MICROCONTROLLER

RC2/CCP1

RC5/SDO

RC3/SCK/SCL

LTC6903

0.01µF

GND

SDI

SCK

SEN

POWER-UP CLOCK

FREQUENCY IS 1039Hz

10Ω

10k

CLK

69034 TA01

CLK

OSC2/CLKOUT

OSC1/CLKIN

MCLR/V

P–P

1µF

0.1µF

FREQUENCY ERROR (%)

–1.0

UNITS

–0.5

69034 TA01b

0 0.5 1.0

= 3V

= 25°C

f = 1039Hz

443

UNITS

TESTED

LTC6903 Frequency Error

Distribution

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

ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property

of their respective owners. Protected by U.S. Patents, including 6342817 and 6614313.

Summary of content (14 pages)

PAGE 1
LTC6903/LTC6904 1kHz to 68MHz Serial Port Programmable Oscillator Features n n n n n n n n n n n n Description 1kHz to 68MHz Square Wave Output 0.5% (Typ) Initial Frequency Accuracy Frequency Error <1.1% Over All Settings 10ppm/°C Typical Frequency Drift Over Temperature 0.1% Resolution 1.7mA Typical Supply Current (f < 1MHz, VS = 2.7V) 2.7V to 5.5V Single- Supply Operation Jitter <0.
PAGE 2
LTC6903/LTC6904 Absolute Maximum Ratings (Note 1) Total Supply Voltage (V+ to GND).................................6V Maximum Voltage on any Pin.............. (GND – 0.3V) ≤ VPIN ≤ (V+ + 0.3V) Output Short-Circuit Duration (Note 2)............. Indefinite Operating Temperature Range (Note 3) LTC6903CMS8/LTC6904CMS8.............–40°C to 85°C LTC6903IMS8/LTC6904IMS8...............–40°C to 85°C LTC6903HMS8/LTC6904HMS8.......... –40°C to 125°C LTC6904MPMS8................................
PAGE 3
LTC6903/LTC6904 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. V+ = 2.7V to 5.5V, GND = 0V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS ∆fi Initial Frequency Accuracy f = 1.039kHz, V+ = 3V, C MIN ∆f Total Frequency Accuracy (Note 7) Single Output Active: Over All Settings, V+ = 2.7V, CLOAD = 5pF Over All Settings, V+ = 5.5V, CLOAD = 5pF TYP MAX UNITS ±0.75 % 0.5 0.5 1.1 1.
PAGE 4
LTC6903/LTC6904 Serial Port Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. V+ = 2.7V to 5.5V, GND = 0V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN VIH Min High Level Input Voltage SEN, SCK, SDI Pins l VIL Max Low Level Input Voltage SEN, SCK, SDI Pins l IIN Digital Input Leakage SEN, SCK, SDI Pins l TYP MAX UNITS 0.67 V+ V 0.
PAGE 5
LTC6903/LTC6904 Typical Performance Characteristics Differential Nonlinearity Frequency vs Temperature 0.10 0.8 0.8 0.08 0.6 0.06 0.4 0.04 0.6 0.4 0.2 0 –0.2 –0.4 –0.6 –0.8 –1.0 0 200 400 600 DAC SETTING 800 0.2 0 –0.2 –0.4 –0.02 –0.04 –0.06 –0.08 0 200 400 600 DAC SETTING 800 –0.10 –40 –20 1000 100 120 Output Resistance vs Supply Voltage 60 10 V+ = 3V 9 50 OUTPUT RESISTANCE (Ω) SUPPLY CURRENT (mA) 8 0.
PAGE 6
LTC6903/LTC6904 Pin Functions GND (Pin 1): Negative Power Supply (Ground). Should be tied directly to a ground plane for best performance. CLK (Pin 5): Auxiliary Clock Output. Frequency set by serial port. SDI (Pin 2): Serial Data Input. Data for serial transfer is presented on this pin. CLK (Pin 6): Main Clock Output. Frequency set by serial port. SCK (Pin 3): Serial Port Clock. Input, positive edge triggered. Clocks serial data in on rising edge. SEN (Pin 4): Serial Port Enable (LTC6903 Only).
PAGE 7
LTC6903/LTC6904 Timing Diagrams LTC6903 Timing Diagram SEN SCK SDI D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 69034 TD01 LTC6904 Timing Diagram SDA tSU, DAT tLOW tSU, STA tHD, DAT tBUF tSU, STO tHD, STA 69034 TD02 SCL tHIGH tHD, STA tr tf START CONDITION REPEATED START CONDITION STOP CONDITION START CONDITION LTC6904 Typical Input Waveform— Programming Frequency to 68MHz (ADR Pin Set LOW) ADDRESS 0 0 1 0 1 1 OCT3 OCT2 OCT1 OCT0 DAC9 DAC8 DAC7 DAC6 ADR WR
PAGE 8
LTC6903/LTC6904 Theory of Operation The LTC6903/LTC6904 contain an internal feedback loop which controls a high frequency square wave VCO operating between 34MHz and 68MHz. The internal feedback loop frequency is set over an octave by a 10-bit resistor DAC. The VCO tracks the internal feedback loop frequency and the output frequency of the VCO is divided by one of sixteen possible powers of two. Higher VCO frequencies and lower output divider settings can result in higher output jitter.
PAGE 9
LTC6903/LTC6904 APPLICATIONS INFORMATION Power-Up State Power Supply Bypass When power is first applied to the LTC6903/LTC6904, all register values are automatically reset to 0. This results in an output frequency of 1.039kHz with both outputs active. In order to obtain the accuracies represented in this data sheet, it is necessary to provide excellent bypass on the power supply. Adequate bypass is a 1µF capacitor in parallel with a 0.
PAGE 10
LTC6903/LTC6904 APPLICATIONS INFORMATION Output Control Serial Port Register Description The CLK and CLK outputs of the LTC6903/LTC6904 are individually controllable through the serial port as described in Table 2 below. The low power mode may also be accessed through these control bits. It is preferred that unused outputs be disabled in order to reduce power dissipation and improve accuracy. OCT[3:0] – Frequency Divider Setting.
PAGE 11
LTC6903/LTC6904 APPLICATIONS INFORMATION LTC6904 I2C Interface generated by the slave lets the master know that the latest byte of information was received. The acknowledge related clock pulse is generated by the master. The master releases the SDA line (HIGH) during the acknowledge clock pulse. The slave-receiver must pull down the SDA line during the acknowledge clock pulse so that it remains a stable LOW during the HIGH period of this clock pulse.
PAGE 12
LTC6903/LTC6904 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. MS8 Package 8-Lead Plastic MSOP (Reference LTC DWG # 05-08-1660 Rev F) 0.889 ± 0.127 (.035 ± .005) 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.65 (.0256) BSC 0.42 ± 0.038 (.0165 ± .0015) TYP 8 7 6 5 0.52 (.0205) REF RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 3.00 ± 0.102 (.118 ± .004) (NOTE 4) 4.90 ± 0.152 (.193 ± .
PAGE 13
LTC6903/LTC6904 Revision History (Revision history begins at Rev D) REV DATE DESCRIPTION D 12/11 Corrected LTC6903 Timing Diagram. PAGE NUMBER 7 Corrected references to Frequency Setting Information section within Serial Port Register Description section. 10 E 3/12 Updated Absolute Maximum Ratings and Order Information. 2 Revised Notes 3 and 4 in Timing Characteristics. 4 69034fe Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
PAGE 14
LTC6903/LTC6904 Typical Application Wide Range Time Interval Generator (1.97 Seconds to 4 Microseconds) 1 fCLK + < TRIGGER PULSE WIDTH < OUTPUT PULSE WIDTH 2 TRIG V+ 1 SDI SCK SEN 2 3 4 GND V+ SDI OE U6 LTC6903 SCK CLK SEN CLK 8 3 C2 0.1µF 4 D PS Q U4 CLK R 1 Q 5 6 74HC74-A PHILIPS SEMICONDUCTOR C1, 0.1µF 7 V 6 10 fCLK + 16 CLK Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 Q11 Q12 5 11 MR 8 S0 S1 S2 V C3 0.