AD9870 View Datasheet(PDF) - Analog Devices
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AD9870 Datasheet PDF : 20 Pages
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AD9870
SERIAL PERIPHERAL INTERFACE (SPI)
The Serial Peripheral Interface (SPI) is a bidirectional serial port. It is used to load configuration information into the registers listed
below as well as to read back their contents. Table I provides a list of the registers that may be programmed through the SPI port.
Addresses and default values are given in hexadecimal form.
Table I. SPI Address Map
Address Bit
(Hex) Breakdown
Width Default Value Name
Description
POWER CONTROL REGISTERS
0x00 (7:0)
8
0xFF
STBY
Standby Control Bits (REF, LO, CKO, CK, GC, LNAMX, VGA, ADC).
0x01
(7:6)
(5:4)
(3:2)
(1:0)
2
0
2
0
2
0
2
1
LNAB
MIXB
CKOB
ADCB
LNA Bias Current (0 = 0.5 mA, 1 = 1 mA, 2 = 2 mA, 3 = 3 mA).
Mixer Bias Current (0 = 1 mA, 1 = 2 mA, 2 = 3 mA, 3 = 4 mA).
CK Oscillator Bias (0 = 0.25 mA, 1 = 0.35 mA, 2 = 0.53 mA, 3 = 0.85 mA).
ADC Amplifier Bias (0 = 2.4 mA, 1 = 3.2 mA, 2 = 4.0 mA, 3 = 4.8 mA).
0x02 (7:0)
8
0x00
TEST
Factory Test Mode.
AGC
0x03
(7)
(6:0)
1
0
7
0x3F
ATTEN
Apply 16 dB attenuation in the front end.
AGCG(14:8) AGC Gain Setting (7 MSBs of a 15-bit two’s-complement word).
0x04 (7:0)
8
0xFF
AGCG(7:0) AGC Gain Setting (8 LSBs of a 15-bit two’s-complement word).
Default corresponds to maximum gain.
0x05
(7:4)
(3:0)
4
0
4
0
AGCA
AGCD
AGC Attack Time Setting. Default yields 50 Hz raw loop bandwidth.
AGC Decay Time Setting. Default is decay time = attack time.
0x06
(7:4)
(3:0)
(2:0)
4
0
4
0
3
0
AGCO
AGCD
AGCR
AGC Overload Update Setting. Default is slowest update.
Fast AGC (Minimizes resistance seen between GCN and GCP).
AGC Enable/Reference Level (disabled, 3 dB, 6 dB, 9 dB, 12 dB, 15 dB below clip).
DECIMATION FACTOR
0x07 (3:0)
4
4
M
Decimation Factor = 60 × (M + 1). Default is decimate-by-300.
LO SYNTHESIZER
0x08 (5:0)
6
0x00
LOR(13:8) Reference Frequency Divisor (6 MSBs of a 14-Bit Word).
0x09 (7:0)
0x0A
(7:5)
(4:0)
8
0x38
3
0x5
5
0x00
LOR(7:0)
LOA
LOB(12:8)
Reference Frequency Divisor (8 LSBs of a 14-Bit Word).
Default (56) Yields 300 kHz from fREF = 16.8 MHz.
“A” Counter (Prescaler Control Counter).
“B” Counter MSBs (5 MSBs of a 13-Bit Word).
Default LOA and LOB Values Yield 300 kHz from 73.35 MHz–2.25 MHz.
0x0B (7:0)
8
0x1D
LOB(7:0) “B” Counter LSBs (8 LSBs of a 13-Bit Word).
0x0C
(6)
(5)
(4:2)
(1:0)
1
0
1
0
3
0
2
0
LOF
LOINV
LOI
LOTM
Enable Fast Acquire.
Invert Charge Pump (0 = Pump_Up ⇒ IOUTL Sources Current).
Charge Pump Current in Normal Operation. IPUMP = (LOI + 1) × 0.625 mA.
Manual Control of LO Charge Pump (3 = Off, 2 = Down, 1 = Up, 0 = Normal).
0x0D (3:0)
4
0x0
LOFA(13:8) LO Fast Acquire Time Unit (4 MSBs of a 14-Bit Word).
0x0E (7:0)
8
0x04
LOFA(7:0) LO Fast Acquire Time Unit (8 LSBs of a 14-Bit Word).
CLOCK SYNTHESIZER
0x10 (5:0)
6
00
CKR(13:8) Reference Frequency Divisor (6 MSBs of a 14-Bit Word).
0x11 (7:0)
8
0x38
CKR(7:0)
Reference Frequency Divisor (8 LSBs of a 14-Bit Word).
Default Yields 300 kHz from fREF =16.8 MHz.
Min = 3, Max = 16383.
0x12 (4:0)
5
0x00
CKN(12:8) Synthesized Frequency Divisor (5 MSBs of a 13-Bit Word).
REV. 0
–5–
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