CIRRUS CS5451A-ISZ

CS5451A
Six-channel, Delta-sigma Analog-to-digital Converter
Features
Description
• Synchronous Sampling
• On-chip 1.2 V Reference (25 ppm/°C typ.)
• Power Supply Configurations:
The CS5451A is a highly integrated delta-sigma (∆Σ) analog-to-digital converter (ADC) developed for the power
measurement industry. The CS5451A combines six ∆Σ
ADCs, decimation filters, and a serial interface on a single chip. The CS5451A interfaces directly to a current
transformer or shunt to measure current, and to a resistive divider or transformer to measure voltage. The
product features a serial interface for communication
with a microcontroller or DSP. The product is initialized
and fully functional upon reset, and includes a voltage
reference.
- VA+ = +3 V; VA- = -2 V; VD+ = +3 V
- Supply Tolerances: ±10%
• Power Consumption
- 23 mW Typical at VD+ = +3 V
• Simple Four-wire Serial Interface
• Charge pump driver output generates
negative power supply.
• Ground-referenced Bipolar Inputs
VIN1+
VIN1IIN2+
IIN2VIN2+
VIN2-
IIN3+
IIN3VIN3+
VIN3VREFIN
VREFOUT
RESET
VD+
x1, 20
4th Order ∆Σ Modulator
Decimation Filter
x1
4th Order ∆Σ Modulator
Decimation Filter
x1, 20
4th Order ∆Σ Modulator
Decimation Filter
SE
4th Order ∆Σ Modulator
x1
OWRS
Decimation Filter
Serial
Interface
4th Order ∆Σ Modulator
x1, 20
SDO
FSO
Decimation Filter
SCLK
4th Order ∆Σ Modulator
x1
Decimation Filter
x1
Voltage
Reference
AGND
http://www.cirrus.com
See page 13.
VA+
GAIN
IIN1+
IIN1-
ORDERING INFORMATION:
Clock
VA-
XIN
Copyright © Cirrus Logic, Inc. 2005
(All Rights Reserved)
Pulse Output
Regulator
CPD
DGND
AUG ‘05
DS635F2
CS5451A
TABLE OF CONTENTS
1. PIN DESCRIPTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. CHARACTERISTICS AND SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. THEORY OF OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4. FUNCTIONAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1 Analog Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.2 Digital Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.3 Performing Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.4 Serial Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.5 System Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.6 Voltage Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.7 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5. PACKAGE DIMENSIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6. ORDERING INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7. ENVIRONMENTAL, MANUFACTURING, & HANDLING INFORMATION . . . . . . . . . . . . . . . 13
8. REVISION HISTORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
LIST OF FIGURES
Figure 1. Serial Port Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 2. Typical Connection Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 3. One Data Frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Figure 4. Serial Port Data Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Figure 5. Generating VA- with a Charge Pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2
DS635F2
CS5451A
PIN DESCRIPTION
Serial Clock Output
SCLK
1
28
VD+
Digital Supply
Serial Data Output
SDO
2
27
DGND
Digital Ground
Frame Sync
FSO
3
26
CPD
Charge Pump Drive
Serial Port Enable
SE
4
25
XIN
Master Clock
Current Input Gain
GAIN
5
24
RESET Reset
Analog Ground
AGND
6
23
OWRS Output Word Rate Select
Reference Input
VREFIN
7
22
VIN1+
Differential Voltage Input 1
Reference Output VREFOUT
8
21
VIN1-
Differential Voltage Input 1
20
IIN1+
Differential Current Input 1
19
IIN1-
Differential Current Input 1
CS5451A
1.
Positive Analog Supply
VA+
9
Negative Analog Supply
VA -
10
Differential Voltage Input 3
VIN3+
11
18
VIN2+
Differential Voltage Input 2
Differential Voltage Input 3
VIN3-
12
17
VIN2-
Differential Voltage Input 2
Differential Current Input 3
IIN3+
13
16
IIN2+
Differential Current Input 2
Differential Current Input 3
IIN3-
14
15
IIN2-
Differential Current Input 2
Clock Generator
Master Clock Input
25
XIN - External clock signal or oscillator input.
Control Pins and Serial Data I/O
Serial Clock Output
1
SCLK - Serial port clock signal that determines the output data rate for SDO pin. Rate of SCLK is
dependent on the XIN frequency and state of OWRS pin.
Serial Data Output
2
SDO -Serial port data output pin. Data will be output at a rate defined by SCLK.
Frame Sync
3
FSO - Framing signal indicates when data samples are about to be transmitted on the SDO pin.
Serial Port Enable
4
SE - When SE is low, the output pins of the serial port are tri-stated.
Current Input Gain
5
GAIN - A logic high sets current channel gain to 1, a logic low sets the gain to 20. If no connection
is made to this pin, it will default to logic low level (through internal 200 kΩ resistor to DGND).
23
OWRS - A logic low sets the output word rate (OWR) to XIN/2048 (Hz). A logic high sets the
OWR to XIN/1024 (Hz). If no connection is made to this pin, then OWRS will default to logic low
level (through internal 200 kΩ resistor to DGND).
24
RESET - Low activates Reset, all internal registers are set to their default states.
Output Word Rate Select
Reset
Analog Inputs/Outputs
Voltage Reference Input
7
VREFIN - The input to this pin establishes the voltage reference for the on-chip modulator.
Voltage Reference Output
8
VREFOUT - The on-chip voltage reference output. The voltage reference has a nominal magnitude of 1.2 V and is referenced to the AGND pin on the converter.
Differential Voltage Inputs
11,12 VIN3+, VIN3- - Differential analog input pins for the voltage channel 3.
18,17 VIN2+, VIN2- - Differential analog input pins for the voltage channel 2.
22,21 VIN1+, VIN1- - Differential analog input pins for the voltage channel 1.
Differential Current Inputs
13,14 IIN3+, IIN3- - Differential analog input pins for the current channel 3.
16,15 IIN2+, IIN2- - Differential analog input pins for the current channel 2.
20,19 IIN1+, IIN1- - Differential analog input pins for the current channel 1.
Power Supply Connections
Analog Ground
6
AGND - Analog ground.
Positive Analog Supply
9
VA+ - The positive analog supply. Typical +3 V ±10% relative to AGND.
Negative Analog Supply
10
VA- - The negative analog supply. Typical -2 V ±10% relative to AGND.
Charge Pump Drive
26
CPD - Designed to drive external charge pump circuitry that will produce a negative analog supply (VA-)voltage.
Digital Ground
27
DGND - Digital Ground.
Positive Digital Supply
28
VD+ - The positive digital supply. Typical +3 V ±10% relative to AGND.
DS635F2
3
CS5451A
2.
CHARACTERISTICS AND SPECIFICATIONS
RECOMMENDED OPERATING CONDITIONS
Parameter
DC Power Supplies
Positive Digital
Positive Analog
Negative Analog
Voltage Reference Input
Symbol
Min
Typ
Max
Unit
VD+
VA+
VA-
2.7
2.7
-2.2
3.0
3.0
-2.0
3.3
3.3
-1.8
V
V
V
VREF+
-
1.2
-
V
ANALOG CHARACTERISTICS
•
•
•
•
Min/Max characteristics and specifications are guaranteed over all Operating Conditions.
Typical characteristics and specifications are measured at nominal supply voltages and TA = 25 °C.
VA+ = VD+ = 3 V ±10%; VA- = -2 V ±10%; AGND = DGND = 0 V; VREFIN = +1.2 V. All voltages with respect to 0 V.
XIN = 4.096 MHz.
Parameter
Symbol
Min
Typ
Max
Unit
THD
74
-
-
dB
CMRR
80
-
-
dB
VA-
-
VA+
V
-
XIN/4
-
Hz
Accuracy (All Channels)
Total Harmonic Distortion
Common Mode Rejection
(DC, 50, 60 Hz)
Common Mode + Signal on Input
Input Sampling Rate
Analog Inputs (Note 1)
Differential Input Voltage Range
[(IIN+) - (IIN-)] or [(VIN+) - (VIN-)]
Gain=20
Gain=1
VIN
VIN
-
80
1.6
-
mVP-P
VP-P
Bipolar Offset
Gain=20
Gain=1
VOS
VOS
-
±11.5
±0.5
±20
±4.0
mV
mV
-
-105
-
dB
Crosstalk (Channel-to-channel)
Input Capacitance
Effective Input Impedance
Noise (Referred to Input)
0-60 Hz
0-1 kHz
0-2 kHz
(50, 60 Hz)
Gain = 20
Gain = 1
IC
IC
-
-
20
1
pF
pF
Gain=20
Gain=1
EII
EII
50
500
60
600
-
kΩ
kΩ
-
-
1
20
2.5
50
3.75
75
µVrms
µVrms
µVrms
µVrms
µVrms
µVrms
1.15
1.2
1.25
V
-
25
50
ppm/°C
Gain=20
Gain=1
Gain=20
Gain=1
Gain=20
Gain=1
Reference Output
Output Voltage
REFOUT
Temperature Coefficient
∆VR
-
6
10
mV
PSRR
60
-
-
dB
VREF+
1.15
1.2
1.25
V
Input Capacitance
-
-
10
pF
Input CVF Current
-
-
1
µA
Load Regulation
(Output Current 1 µA Source or Sink)
Power Supply Rejection
Reference Input
Input Voltage Range
4
DS635F2
CS5451A
ANALOG CHARACTERISTICS (continued)
Parameter
Symbol
Min
Typ
Max
Unit
PSCA
PSCD
PSCD
-
4.0
5.0
1.0
5.3
6.3
1.5
mA
mA
mA
PC
PC
-
27
23
35
31
mW
mW
PSRR
PSRR
PSRR
50
50
60
65
90
-
dB
dB
dB
Power Supplies
Power Supply Currents
IA+
ID+ with CPD
Typical VA+ = VD+ = +3 V; VA- = -2 V
ID+ without CPD
Power Consumption
(Note 2)
With CPD
Without CPD
Power Supply Rejection
50, 60 Hz (Note 3)
50, 60 Hz (Note 3)
(DC)
Voltage Channel
Current Channel
Notes: 1. Specifications for Gain = 20 apply only to Current Channels. Voltage Channels are fixed to Gain = 1
2.
3.
All outputs unloaded. All inputs CMOS level.
Definition for PSRR: VREFIN tied to VREFOUT, VA+ = VD+ = 3 V, AGND = DGND = 0 V, VA- = -2 V (using chargepump circuit with CPD). In addition, a 106.07 mV rms (60 Hz) sinewave is imposed onto the VA+ and VD+ pins.
The “+” and “-” input pins of both input channels are shorted to VA-. 2048 instantaneous digital output data words
are collected for the channel under test. The rms value of the digital sinusoidal output signal is calculated, and this
rms value is converted into the rms value of the sinusoidal voltage (measured in mV) that would need to be applied
at the channel’s inputs, in order to cause the same digital sinusoidal output. This voltage is then defined as Veq.
PSRR is then (in dB):
⎧ 106.07 ⎫
PSRR = 20 ⋅ log ⎨ ------------------ ⎬
⎩ V eq ⎭
DIGITAL CHARACTERISTICS (See Note 4)
•
•
•
•
Min/Max characteristics and specifications are guaranteed over all Operating Conditions.
Typical characteristics and specifications are measured at nominal supply voltages and TA = 25 °C.
VA+ = VD+ = 3V ±10%; VA- = -2 V ±10%; AGND = DGND = 0 V. All voltages with respect to 0 V.
XIN = 4.096 MHz
Parameter
Symbol
Min
Typ
Max
Unit
XIN
3
4.096
5
MHz
40
-
60
%
OWR
OWR
-
XIN/2048
XIN/1024
-
Hz
Hz
High-Level Input Voltage
VIH
0.6 VD+
-
VD+
V
Low-Level Input Voltage
VIL
0.0
-
0.8
V
Master Clock Characteristics
Master Clock Frequency
Master Clock Duty Cycle
Filter Characteristics
High Rate Filter Output Word Rate
OWRS = 0
OWRS = 1
Input/Output Characteristics
High-Level Output Voltage
Iout = -5.0 mA
VOH
(VD+) - 1.0
-
-
V
Low-Level Output Voltage
Iout = 5.0 mA
VOL
-
-
0.4
V
Iin
-
±1
±10
µA
3-State Leakage Current
IOZ
-
-
±10
µA
Digital Output Pin Capacitance
Cout
-
9
-
pF
Input Leakage Current
(Note 5)
Notes: 4. All measurements performed under static conditions.
5.
DS635F2
For OWRS and GAIN pins, input leakage current is 30 µA (Max).
5
CS5451A
SWITCHING CHARACTERISTICS
•
•
•
•
Min/Max characteristics and specifications are guaranteed over all Operating Conditions.
Typical characteristics and specifications are measured at nominal supply voltages and TA = 25 °C.
VA+ = VD+ = 3 V ±10%; VA- = -2 V ±10%; AGND = DGND = 0 V. All voltages with respect to 0 V.
Logic Levels: Logic 0 = 0 V, Logic 1 = VD+
Symbol
Min
Typ
Max
Unit
Rise Times
(Note 6)
Parameter
Any Digital Input (except XIN)
XIN only
Any Digital Output
trise
-
50
1.0
10
-
µs
ns
ns
Fall Times
(Note 6)
Any Digital Input (except XIN)
XIN only
Any Digital Output
tfall
-
50
1.0
10
-
µs
ns
ns
SCLK
SCLK
-
500
1000
-
kHz
kHz
t1
t2
-
0.5
0.5
-
SCLK
SCLK
t3
-
-
50
ns
t4
-
0.5
-
SCLK
Serial Port Timing
Serial Clock Frequency
(Note 7)
OWRS = “0”
OWRS = “1”
Serial Clock
(Note 7 and 8)
Pulse Width High
Pulse Width Low
SCLK falling to New Data Bit
FSO Falling to SCLK Rising Delay
(Note 7 & 8)
FSO Pulse Width
(Note 7 & 8)
t5
-
1
-
SCLK
(Note 9)
t6
-
-
50
ns
t7
-
-
50
ns
SE Rising to Output Enabled
SE Falling to Output in Tri-state
Notes: 6. Specified using 10% and 90% points on wave-form of interest. Output loaded with 50 pF.
7.
8.
9.
Device parameters are specified with XIN = 4.096 MHz.
Device parameters are specified with OWRS = 1.
After SE is asserted, the states of SDO and SCLK are FSO is undefined.
MSB(V1)
SDO
MSB(V1) - 1
t3
t1
LSB(I3)
t2
SCLK
t4
FSO
t5
t7
SE
t6
Figure 1. Serial Port Timing
6
DS635F2
CS5451A
ABSOLUTE MAXIMUM RATINGS
WARNING: Operation at or beyond these limits may result in permanent damage to the device.
Normal operation is not guaranteed at these extremes.
Parameter
Symbol
Min
Typ
Max
Unit
DC Power Supplies
Positive Digital
Positive Analog
Negative Analog
VD+
VA+
VA-
-0.3
-0.3
-2.5
-
+3.5
+3.5
-0.3
V
V
V
Input Current, Any Pin Except Supplies
(Note 10 and 11)
IIN
-
-
±10
mA
IOUT
-
-
±25
mA
(Note 12)
PDN
-
-
500
mW
Analog Input Voltage
All Analog Pins
VINA
(VA-) - 0.3
-
(VA+) + 0.3
V
Digital Input Voltage
All Digital Pins
VIND
-0.3
-
(VD+) + 0.3
V
Ambient Operating Temperature
TA
-40
-
85
°C
Storage Temperature
Tstg
-65
-
150
°C
Output Current
Power Dissipation
Notes: 10. Applies to all pins including continuous over-voltage conditions at the analog input (AIN) pins.
11.
Transient current of up to 100 mA will not cause SCR latch-up. Maximum input current for a power supply pin is
±50 mA.
12. Total power dissipation, including all input currents and output currents.
DS635F2
7
CS5451A
3. THEORY OF OPERATION
The CS5451A is a six-channel analog-to-digital converter (ADC) followed by a serial interface that allows communication with a target device. The analog inputs are
structured for 3-phase power meter applications, with
three dedicated voltage and current channels. Figure 2
illustrates the CS5451A typical inputs and power supply
connections.
The voltage-sensing element introduces a voltage
waveform on the voltage channel inputs VIN(1-3)± and
is subject to a fixed 1x gain amplifier. A fourth-order delta-sigma modulator samples the amplified signal for digitization.
Simultaneously, the current-sensing element introduces
a voltage waveform on the current channel input
IIN(1-3)± and is subject to two selectable gains of the
programmable gain amplifier (PGA). The amplified signal is sampled by a fourth-order delta-sigma modulator
for digitization. Both converters sample at a rate of
XIN/8, the over-sampling provides a wide dynamic
range and simplified anti-alias filter design.
The decimating digital filters on all channels are Sinc3
filters. The single bit data is passed to the low-pass decimation filter and output at a fixed word rate. The decimation rate is selectable for two output word rates.
The 16-bit output word is then transmitted via a master
serial data port. The six-channel data is multiplexed on
the serial data output and is preceded by a frame sync
signal.
+3 V
VA+
VD+
REFIN
Optional
External
Reference
V
1.2 V
REFOUT
VIN1+, VIN2+, or VIN3+
+
PHASE
VIN1-, VIN2-, or VIN3-
IIN1+, IIN2+, or IIN3+
I PHASE
NOTE: Current input channels
actually measure voltage.
IIN1-, IIN2-, or IIN3-
AGND
VA-
DGND
-2 V
Figure 2. Typical Connection Diagram
8
DS635F2
CS5451A
4.
4.1
FUNCTIONAL DESCRIPTION
Analog Inputs
The CS5451A is equipped with six fully differential input
channels. The inputs VIN(1-3)± and IIN(1-3)± are designated as the voltage and current channel inputs, respectively. The full-scale differential input voltage for
the current and voltage channel is ±800 mVP
(gain = 1x).
4.1.1
Voltage Channel
800mV P
----------------- ≅ 565.69mVRMS
2
which is approximately 70.7% of maximum peak voltage.
Current Channel
The output of the current sense resistor or transformer
is connected to the IIN(1-3)+ and IIN(1-3)- input pins of
the CS5451A. To accommodate different current-sensing devices the current channels incorporates a programmable gain amplifier (PGA) that can be set to one
of two input ranges. Input pin GAIN (see Table 1) define
the PGA’s two gain selections and corresponding maximum input signal level.
GAIN
Maximum Input Range
0
±40mV
20x
1
±800mV
1x
Table 1. Current Channel PGA Setting
4.2
Digital Filters
The decimating digital filter samples the modulator bit
stream at XIN/8 and produces a fixed output word rate.
The digital filters are implemented as sinc3 filters with
the following transfer function:
⎛ 1 – z – DR⎞
H ( z ) = ⎜ ----------------------⎟
⎝ 1 – z–1 ⎠
DS635F2
The output word rate (OWR) is selected by the OWRS
pin and defined by Table 2.
OWRS
DR
Output Word Rate
0
256
XIN/2048
1
128
XIN/1024
Table 2. Decimation Filter OWR
4.3
The output of the line voltage resistive divider or transformer is connected to the VIN(1-3)+ and VIN(1-3)- input pins of the CS5451A. The voltage channels are
equipped with a 1x fixed gain amplifier. The full-scale
signal level that can be applied to the voltage channel is
±800 mV. If the input signal is a sine wave the maximum
RMS voltage is:
4.1.2
The decimation rate is determined by the exponent DR
(see Table 2).
Performing Measurements
The ADC outputs are transferred in 16-bit, signed (two’s
complement) data formats. Table 3 defines the relationship between the differential voltage applied to any one
of the input channels and the corresponding output
code. Note that for the current channels, the state of the
GAIN input pin is assumed to driven low such that the
PGA gain on the current channels is 1x. If the PGA gain
of the current channels is set to 20x, a +40 mV voltage
is applied to any pair of IIN(1-3)± pins would cause an
output code of 32767.
Differential Input
Voltage (mV)
Output Code
(hexadecimal)
Output Code
(decimal)
+800
7FFF
32767
0.0122 to 0.0366
0001
1
-0.0122 to 0.0122
0000
0
-0.0122 to -0.0366
FFFF
-1
-800
8000
-32768
Notes: Assume PGA gain is set to 1x.
Table 3. Differential Input Voltage vs. Output Code
4.4
Serial Interface
The CS5451A communicates with a target device via a
master serial data output port. Output data is provided
on the SDO output synchronous with the SCLK output.
A third output, FSO, is a framing signal used to signal
the start of output data. These three outputs will be driven as long as the SE (serial enable) input is held high.
Otherwise, these outputs will be high-impedance.
Data out (SDO) changes as a result of SCLK falling, and
always outputs valid data on the rising edge of SCLK.
When data is being transferred the SCLK frequency is
XIN/8 when OWRS is low or XIN/4 when OWRS is high.
3
9
CS5451A
96 SCLKs
SCLK
FSO
15 14 13 12 11 10 9
8 7 6
5
4 3
2 1
0 15 14 13 12 11 10 9 8
7 6 5 4
3 2 1 0 15 14
SDO
[ Low ]
Channel 1 ( V )
Channel 1 ( I )
...
...
...
...
...
... 3 2 1 0
Ch. 2 ( V )... Ch. 2 ( I ) ... Ch. 3 ( V ) ... Ch. 3 ( I )
...
[ Low ]
Figure 3. One Data Frame
When data is not being transferred SCLK is held low.
(see Figure 3.)
RESET is activated, all internal registers are set to a default state.
The framing signal (FSO) output is normally low. FSO
goes high, with a pulse width equal to one SCLK period,
when the instantaneous voltage and current data samples are about to be transmitted out of the serial interface (after each A/D conversion cycle). SCLK is not
active during FSO high.
Upon powering up, the RESET pin must be held low
(active) until after the power stabilizes.
For 96 SCLK periods after FSO falls, SCLK is active and
SDO provides valid output. Six channels of 16-bit data
are output, MSB first. Figure 4 illustrates how the voltage and current measurements are output for the three
phases. SCLK will then be held low until the next sample period.
4.5
System Initialization
A hardware reset is initiated when the RESET pin is
forced low with a minimum pulse width of 50 ns. When
SCLK
4.6
Voltage Reference
The CS5451A is specified for operation with a +1.2 V
reference between the VREFIN and AGND pins. The
converter includes an internal 1.2 V reference that can
be used by connecting the VREFOUT pin to the VREFIN pin of the device. The VREFIN can be used to connect external filtering and/or references.
4.7
Power Supply
The low, stable analog power consumption and superior
supply rejection of the CS5451A allow for the use of a
simple charge-pump negative supply generator. The
use of a negative supply alleviates the need for level
96 SCLKs
FSO
Each data segment
is 16 bits long.
SDO
Channel 1 V
Channel 1 I
Channel 2 V
Channel 3 I
Channel 3 V
Channel 2 I
Figure 4. Serial Port Data Transfer
10
DS635F2
CS5451A
shifting of the analog inputs. The CPD pin and capacitor
C1 provide the necessary analog supply current as
shown in Figure 5. The Schottky diodes D1 and D2 are
chosen for their low forward voltages and high-speed
capabilities. The capacitor C2 provides the required
charge storage and bypassing of the negative supply.
The CPD output signal provides the charge pump driver
signal. The frequency of the charge pump driver signal
is synchronous to XIN. The nominal average frequency
is 1 MHz. The level on the VA- pin is fed back internally
so that the CPD output will regulate the VA- level to -2/3
of VA+ level.
The value of capacitor C1 (see Figure 5) is dependent
on the XIN clock frequency. The 39 nF value for C1 was
selected for a XIN clock frequency equal to 4.096 MHz.
For more information about the operation of this type of
charge pump circuit, the reader can refer to Cirrus Logic, Inc.’s application note AN152: Using the
DS635F2
CPD
AGND
39 nF
C1
VA-
D2
BAT 85
D1
BAT 85
C2
1 µF
Figure 5. Generating VA- with a Charge Pump
CS5521/24/28, and CS5525/26 Charge Pump Drive for
External Loads.
11
CS5451A
5. PACKAGE DIMENSIONS
28L SSOP PACKAGE DRAWING
N
D
E11
A2
E
e
b2
SIDE VIEW
A
∝
A1
END VIEW
L
SEATING
PLANE
1 2 3
TOP VIEW
INCHES
DIM
A
A1
A2
b
D
E
E1
e
L
∝
MIN
-0.002
0.064
0.009
0.390
0.291
0.197
0.022
0.025
0°
NOM
-0.006
0.069
-0.4015
0.307
0.209
0.026
0.0354
4°
MILLIMETERS
MAX
0.084
0.010
0.074
0.015
0.413
0.323
0.220
0.030
0.041
8°
MIN
-0.05
1.62
0.22
9.90
7.40
5.00
0.55
0.63
0°
NOM
-0.13
1.75
-10.20
7.80
5.30
0.65
0.90
4°
NOTE
MAX
2.13
0.25
1.88
0.38
10.50
8.20
5.60
0.75
1.03
8°
2,3
1
1
JEDEC #: MO-150
Notes: 1. “D” and “E1” are reference datums and do not included mold flash or protrusions, but do include mold mismatch
and are measured at the parting line, mold flash or protrusions shall not exceed 0.20 mm per side.
Dimension “b” does not include dambar protrusion/intrusion. Allowable dambar protrusion shall be 0.13 mm total in
excess of “b” dimension at maximum material condition. Dambar intrusion shall not reduce dimension “b” by more
than 0.07 mm at least material condition.
3. These dimensions apply to the flat section of the lead between 0.10 and 0.25 mm from lead tips.
2.
12
DS635F2
CS5451A
6. ORDERING INFORMATION
Model
CS5451A-IS
CS5451A-ISZ (lead free)
Temperature
Package
-40 to +85 °C
28-pin SSOP
7. ENVIRONMENTAL, MANUFACTURING, & HANDLING INFORMATION
Model Number
Peak Reflow Temp
MSL Rating*
Max Floor Life
CS5451A-IS
240 °C
2
365 Days
CS5451A-ISZ (lead free)
260 °C
3
7 Days
* MSL (Moisture Sensitivity Level) as specified by IPC/JEDEC J-STD-020.
8. REVISION HISTORY
Revision
Date
Changes
A1
JUL 2003
Initial Release
PP1
OCT 2003
Initial release for Preliminary Product Information
F1
FEB 2005
Update electrical specifications w/ most-current characterization data.
F2
AUG 2005
Update electrical specifications w/ most-current characterization data. Added
MSL data.
Contacting Cirrus Logic Support
For all product questions and inquiries contact a Cirrus Logic Sales Representative.
To find the one nearest to you go to www.cirrus.com
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to change without notice and is provided “AS IS” without warranty of any kind (express or implied). Customers are advised to obtain the latest version of relevant
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or service marks of their respective owners.
DS635F2
13