KAD5512HP-12Q72 Intersil, KAD5512HP-12Q72 Datasheet - Page 17

• Manufacturer Part Number: KAD5512HP-12Q72
• Description: IC ADC 12BIT 125MSPS SGL 72-QFN
• Manufacturer: Intersil
• Series: FemtoCharge™r

Specifications of KAD5512HP-12Q72

• Number Of Bits: 12
• Sampling Rate (per Second): 125M
• Data Interface: Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 376mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 72-VFQFN Exposed Pad
• For Use With: KDC5512H-Q48EVAL - DAUGHTER CARD FOR KAD5512KDC5512HEVAL - DAUGHTER CARD FOR KAD5512
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Theory of Operation
Functional Description
The KAD5512HP is based upon a 12-bit, 250MSPS A/D
converter core that utilizes a pipelined successive
approximation architecture (Figure 21). The input voltage is
captured by a Sample-Hold Amplifier (SHA) and converted
to a unit of charge. Proprietary charge-domain techniques
are used to successively compare the input to a series of
reference charges. Decisions made during the successive
approximation operations determine the digital code for each
input value. The converter pipeline requires six samples to
produce a result. Digital error correction is also applied,
resulting in a total latency of eight and one half clock cycles.
This is evident to the user as a time lag between the start of
a conversion and the data being available on the digital
outputs.
The KAD5512HP family offers 2.5dB improvement in SNR
over the KAD5512P by simultaneously sampling the input
signal with two ADC cores in parallel and summing the digital
result. Since the input signal is correlated between the two
cores and noise is not, an increase in SNR is achieved. As a
result of this architecture, indexed SPI operations must be
executed on each core in series. Refer to “Indexed Device
Configuration/Control” on page 24 for more details.
Power-On Calibration
The ADC performs a self-calibration at start-up. An internal
power-on-reset (POR) circuit detects the supply voltage
INP
INN
1.25V
17
+
–
SHA
FIGURE 21. ADC CORE BLOCK DIAGRAM
2.5-BIT
FLASH
KAD5512HP
1.5-BIT/STAGE
6-STAGE
ramps and initiates the calibration when the analog and
digital supply voltages are above a threshold. The following
conditions must be adhered to for the power-on calibration to
execute successfully:
• A frequency-stable conversion clock must be applied to
• DNC pins (especially 3, 4 and 18) must not be pulled up or
• SDO (pin 66) must be high
• RESETN (pin 25) must begin low
• SPI communications must not be attempted
A user-initiated reset can subsequently be invoked in the
event that the previous conditions cannot be met at
power-up.
The SDO pin requires an external 4.7kΩ pull-up to OVDD. If
the SDO pin is pulled low externally during power-up,
calibration will not be executed properly.
After the power supply has stabilized the internal POR
releases RESETN and an internal pull-up pulls it high, which
starts the calibration sequence. If a subsequent
user-initiated reset is required, the RESETN pin should be
connected to an open-drain driver with a drive strength of
less than 0.5mA.
the CLKP/CLKN pins
down
LVDS/LVCMOS
CORRECTION
GENERATION
OUTPUTS
DIGITAL
CLOCK
ERROR
1-BIT/STAGE
3-STAGE
FLASH
3-BIT
October 1, 2009
FN6808.3