CTST570QG
CTST570QG Datasheet
CTST570
| Part | Datasheet |
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CTST570QG |
CTST570QG (pdf) |
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| CTST570 Programmable Capacitive Tuning IC SON8 Capacitive Tuning Range of 2.6pF to 14.55pF 0.063pF Minimum Step Size Reprogrammable Through Non- volatile EEPROM Storage May Be Placed in Parallel for Greater Capacitance Values Very Low Supply Current 2.5V to 5.0V Supply Voltage RoHS compliant Pb Free Packages BLOCK DIAGRAM The CTST570 is a digitally programmed capacitor specifically designed to tune a crystal or SAW based oscillator to a desired center frequency. The desired capacitance value for production trimming is set by a serial data stream when placed into a programming mode. The CTST570 is designed to be a labor and cost saving device within the oscillator production process. Using EEPROM technology, the capacitance can be re-tuned as needed during the production process by repeating the programming steps thereby increasing production yield. The CTST570 is available in an SON8 package 1.5mm x 1.0mm for very small form factor oscillators. ENGINEERING NOTES Capacitor Structure The CTST570 capacitance value is composed of three parallel capacitor banks, CF is a fixed capacitor value of 2.6pF and CMID & CLO are variable capacitors of differing ranges and resolutions as seen in Table Capacitors composing CMID and CLO are set with a binary control word through an 11-bit shift register described in “Programming the CTST570” section. The values of each CLO and CMID stepping are detailed in the complete Nominal Capacitance Binary Mapping spreadsheet. CTOTAL = CF + CMID + CLO Table 1 Capacitor Structure Internal Capacitor CF CMID CLO Total Min Value pF Max Value pF Step Size pF North Americas +1-800-757-6686 • International +1-508-435-6831 • Asia +65-655-17551 • Specifications are subject to change without notice. 1 CTST570 Programmable Capacitive Tuning IC SON8 Programing the CTST570 Control Word The capacitance in the CTST570 is controlled by an 11-bit shift register with the data input bit definitions shown in Table The control word data is inputted serially on the rising edge of the CLK signal with bit-0 first and bit10 last. Table 2 CTST570 Control Word Definition bit-10 Not Used bit-9 Not Used bit-8 bit-7 CMID --- 11-bit Control Word bit-6 bit-5 bit-4 bit-3 CLO --- bit-2 PART ORDERING INFORMATION Part Number CTST570QG Package SON8 Marking T YM North Americas +1-800-757-6686 • International +1-508-435-6831 • Asia +65-655-17551 • Specifications are subject to change without notice. 10 |
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