HMCAD1100 Datasheet, PDF (10/26 Pages) Hittite Microwave Corporation – Octal 13/12-Bit 20/40/50 MSPS A/D Co nverter

v03.0611
HMCAD1100
Octal 13/12-Bit 20/40/50 MSPS
A/D Converter
Serial Interface
The HMCAD1100 configuration registers can be accessed through a serial interface formed by the pins SDATA (serial
interface data), SCLK (serial interface clock) and CSN (chip select, active low). The following occurs when CSN is set
low:
• Serial data are shifted into the chip
• At every rising edge of SCLK, the value present at SDATA is latched
• SDATA is loaded into the register every 24th rising edge of SCLK
Multiples of 24-bit words data can be loaded within a single active CSN pulse. If more than 24 bits are loaded into
SDATA during one active CSN pulse, only the first 24 bits are kept. The excess bits are ignored. Every 24-bit word is
divided into two parts:
• The first eight bits form the register address
• The remaining 16 bits form the register data
Acceptable SCLK frequencies are from 20 MHz down to a few hertz. Duty-cycle does not have to be tightly controlled.
Timing Diagram
Figure 4 shows the timing of the serial port interface. Table 5 explains the timing variables used in figure 4.
CSN
SCLK
SDATA
t_cs
t_hitlo
t_ck
t_{s th}
t_chi
t_ch
A7 A6 A5 A4 A3 A2 A1 A0 D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Figure 3. Serial Port Interface timing
Table 4: Serial Port Interface timing definitions
Parameter
Description
Minimum Value
Unit
t_cs
Setup time between CSN and SCLK
8
ns
t_ch
Hold time between CSN and SCLK
8
ns
t_hi
SCLK high time
20
ns
t_lo
SCLK low time
20
ns
t_ck
SCLK period
50
ns
t_s
Data setup time
5
ns
t_h
Data hold time
5
ns
Start up Initialization
As part of the HMCAD1100 power-on sequence both a reset and a power down cycle have to be applied to ensure
correct start-up initialization. Make sure that the supply voltages are properly settled before the start up initialization
is being performed. Reset can be done in one of two ways:
1. By applying a low-going pulse (minimum 20 ns) on the RESETN pin (asynchronous).
2. By using the serial interface to set the ‘rst’ bit high. Internal registers are reset to default values when this
bit is set. The ‘rst’ bit is self-reset to zero. When using this method, do not apply any low-going pulse on the
RESETN pin.
Power down cycling can be done in one of two ways:
1. By applying a high-going pulse (minimum 20 ns) on the PD pin (asynchronous).
For price, delivery and to place orders: Hittite Microwave Corporation, 2 Elizabeth Drive, Chelmsford, MA 01824
978-250-3343 tel • 978-250-3373 fax • Order On-line at www.hittite.com
Application Support: [e-mail]
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