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CS4461
Multi-Bit A/D for Class-D Real-Time PSR Feedback
Features
z Advanced Multi-bit Delta-Sigma Architecture
z Real-time Feedback of Power Supply
Conditions (AC and DC)
z Filterless Digital Output Resulting in Very Low
Signal Delay
z 135 mW Power Consumption
z Supports Logic Levels Between 3.3 V and
5.0 V
z Differential Analog Architecture
z Modulator Overflow Detection
z Interfaces Directly to the CS44800/CS44600
Class-D PWM Modulator
z Multi-bit Conversion at up to 7.5 MHz
z Delivers Modulated Data Over 2-Wire Interface
General Description
The CS4461 is a complete analog-to-digital converter
for class-D real-time power supply rejection (PSR) feed-
back. It performs sampling and analog-to-digital
conversion, generating digital data for input to a
class-D modulator with real-time PSR feedback
capabilities.
The CS4461 uses a 5th-order, multi-bit delta-sigma
modulator followed by output data formatting. The ADC
uses a differential architecture which provides excellent
noise rejection.
The CS4461 feeds back the AC and DC voltage compo-
nents and is ideal for class-D audio systems requiring
high power supply rejection.
The CS4461 is available in a 24-pin TSSOP package in
both Commercial (-10° to +70° C) and Automotive
grade (-40° to +85° C). The CDB44800 Customer Dem-
onstration board is also available for device evaluation
and implementation suggestions. Please see “Ordering
Information” on page 11 for complete details.
FILT+
VQ REFGND
Voltage Reference
PSR_RESET PSR_EN
AIN+
AIN-
+
-
S/H
LP Filter
DAC
∆Σ
Output Data
Formatting
OVERFLOW
PSR_MCLK
PSR_SYNC
PSR_DATA
http://www.cirrus.com
5.0 V
(VA)
GND
3.3 V to 5.0 V
(VDP)
Copyright © Cirrus Logic, Inc. 2005
(All Rights Reserved)
SEPTEMBER '05
DS650F1

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CS4461
TABLE OF CONTENTS
1. CHARACTERISTICS AND SPECIFICATIONS ..................................................................................... 3
2. PIN DESCRIPTIONS ............................................................................................................................. 6
3. TYPICAL CONNECTION DIAGRAM .................................................................................................... 7
4. APPLICATIONS .................................................................................................................................... 8
4.1 Digital Connections ......................................................................................................................... 8
4.2 Analog Connections ....................................................................................................................... 8
4.3 Power-Up Sequence ...................................................................................................................... 9
4.4 Overflow Detection ......................................................................................................................... 9
4.5 Grounding and Power Supply Decoupling ...................................................................................... 9
5. PACKAGE DIMENSIONS ................................................................................................................. 10
6. ORDERING INFORMATION ............................................................................................................... 11
7. REVISION HISTORY ........................................................................................................................... 11
LIST OF FIGURES
Figure 1. Typical Connection Diagram......................................................................................................... 7
Figure 2. CS4461 Recommended Analog Input Buffer................................................................................ 8
2 DS650F1

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CS4461
1. CHARACTERISTICS AND SPECIFICATIONS
(All Min/Max characteristics and specifications are guaranteed over the Specified Operating Conditions. Typical
performance characteristics and specifications are derived from measurements taken at typical supply voltages
and TA = 25°C.)
SPECIFIED OPERATING CONDITIONS
(GND = 0 V, all voltages with respect to 0 V.)
DC Power Supplies:
Parameter
Ambient Operating Temperature
Symbol Min Typ Max Unit
Positive Analog
VA
4.75 5.0 5.25 V
Positive Digital VDP 3.1 3.3 5.25 V
Commercial (-CZZ)
TAC
-10
-
+70 °C
Automotive (-DZZ)
TAA
-40
-
+85 °C
ABSOLUTE MAXIMUM RATINGS
(GND = 0 V, All voltages with respect to ground.) (Note 1)
DC Power Supplies:
Input Current
Parameter
Analog
Digital
(Note 2)
Analog Input Voltage
(Note 3)
Digital Input Voltage
(Note 3)
Ambient Operating Temperature (Power Applied)
Storage Temperature
Symbol
VA
VDP
Iin
VIN
VIND
TA
Tstg
Min
-0.3
-0.3
-
GND - 0.7
-0.7
-50
-65
Max
+6.0
+6.0
±10
VA + 0.7
VDP + 0.7
+95
+150
Units
V
V
mA
V
V
°C
°C
Notes:
1. Operation beyond these limits may result in permanent damage to the device.
Normal operation is not guaranteed at these extremes.
2. Any pin except supplies. Transient currents of up to ±100 mA on the analog input pins will not cause
SCR latch-up.
3. The maximum over/under voltage is limited by the input current.
DS650F1
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DC ELECTRICAL CHARACTERISTICS
(GND = 0 V, all voltages with respect to ground.
PSR_MCLK=12.288 MHz)
Parameter
Power Supply Current
(Normal Operation)
VA
VDP = 5.0 V
VDP = 3.3 V
Power Supply Current
(Power-Down Mode) (Note 4)
VA
VDP = 5.0 V
Power Consumption
(Normal Operation)
(Power-Down Mode)
VDP = 5.0 V
VDP = 3.3 V
VDP = 5.0 V
ADC Power Supply Rejection Ratio (1 kHz)
(Note 5)
VQ Nominal Voltage
Output Impedance
Maximum allowable DC current source/sink
FILT+ Nominal Voltage
Output Impedance
Maximum allowable DC current source/sink
Symbol
IA
ID
ID
IA
ID
PSRR
Min
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
Typ
17.5
22
14.5
2
2
198
135
20
65
2.5
25
0.01
5
18
0.01
CS4461
Max
21
26
17
-
-
235
161
-
-
-
-
-
-
-
-
Unit
mA
mA
mA
mA
mA
mW
mW
mW
mW
dB
V
k
mA
V
k
mA
Notes:
4. Power Down Mode is defined as PSR_RESET = Low with all clocks and data lines held static.
5. Valid with the recommended capacitor values on FILT+ and VQ as shown in the Typical Connection
Diagram.
DIGITAL CHARACTERISTICS
Parameter
High-Level Input Voltage
Low-Level Input Voltage
High-Level Output Voltage at Io = 100 µA
Low-Level Output Voltage at Io = 100 µA
OVERFLOW Current Sink
Input Leakage Current
THERMAL CHARACTERISTICS
Parameter
Allowable Junction Temperature
Junction to Ambient Thermal Impedance
(% of VDP)
(% of VDP)
(% of VDP)
(% of VDP)
Symbol
VIH
VIL
VOH
VOL
IOVERFLOW
Iin
Min
70%
-
70%
-
-
-
Typ Max Units
--
V
- 30%
V
--
V
- 15%
V
- 4.0 mA
- ±10 µA
Symbol
θJA
Min
-
-
Typ
-
70
Max
135
-
Unit
°C
°C/W
4 DS650F1

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CS4461
ANALOG CHARACTERISTICS
(Test conditions (unless otherwise specified): Input test signal is a 1 kHz sine wave; measurement bandwidth is
10 Hz to 20 kHz.)
Parameter
DC Accuracy
Gain Error
Gain Drift
Analog Input Characteristics
Full-scale Differential Input Voltage
AIN+/AIN- Input Range
(VA = 5.0 V)
Input Impedance (Differential)
Common Mode Rejection Ratio
Symbol Min
-CZZ
-DZZ
-CZZ
-DZZ
(Note 6)
CMRR
-
-
-
1.1
1.1
18
-
Typ
-
±100
1.13*VA
1.13*VA
-
-
-
82
Max
±5
-
-
-
3.9
3.9
-
-
Unit
%
ppm/°C
VPP
VPP
V
V
k
dB
Notes:
6. Measured between AIN+ and AIN-
DS650F1
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