A8294 Datasheet

A8294
Single LNB Supply and Control Voltage Regulator
Features and Benefits
Description
▪ 2-wire serial I2C™ -compatible interface: control (write) and
status (read)
▪ LNB voltages (6 programmable levels) compatible with all
common standards
▪ Tracking switch-mode power converter for lowest dissipation
▪ Integrated converter switches and current sensing
▪ Provides up to 700 mA continuous load current
▪ Output current limit of 800 mA minimum, with 48 ms timer
▪ Static current limit circuit allows full current at startup and
13→18 V output transition; reliably starts wide load range
▪ Push-pull output stage minimizes 13→18 V and 18→13 V
output transition times for highly capacitive loads
▪ Adjustable rise/fall time via external timing capacitor
▪ Built-in tone oscillator, factory-trimmed to 22 kHz facilitates
DiSEqC™ tone encoding, even at no-load
▪ Two methods of 22 kHz tone generation, including outgoing
tone verification (TDET)
▪ Auxiliary modulation input
▪ LNB overcurrent with timer
▪ Diagnostics for output voltage level, input supply UVLO,
and DiSEqCTM tone output
Package: 20-contact 4 × 4 mm MLP/QFN (suffix ES)
Intended for analog and digital satellite receivers, this single
low noise block converter regulator (LNBR) is a monolithic
linear and switching voltage regulator, specifically designed to
provide the power and the interface signals to an LNB down
converter via coaxial cable. The A8294 requires few external
components, with the boost switch and compensation circuitry
integrated inside of the device. A high switching frequency is
chosen to minimize the size of the passive filtering components,
further assisting in cost reduction. The high levels of component
integration ensure extremely low noise and ripple figures.
The A8294 has been designed for high efficiency, utilizing
the Allegro™ advanced BCD process. The integrated boost
switch has been optimized to minimize both switching and
static losses. To further enhance efficiency, the voltage drop
across the tracking regulator has been minimized.
For DiSEqC™ communications, several schemes are available
for generating tone signals, all the way down to no-load, and
using either the internal clock or an external time source.
A comprehensive set of fault registers are provided, which
comply with all the common standards, including: overcurrent,
thermal shutdown, undervoltage, and power not good.
Continued on the next page…
Functional Block Diagram
L1
33 μH
VS
D1
C2
100 μF
C1
100 nF
C5
100 μF
VIN
LX
GNDLX
C4
100 nF
C6
1 μF
BOOST VCP
VREG
Boost
Converter
Regulator
EXTM
fsw
VDD
R1 R2 R3 R4
D3
A
Charge
Pump
C3
220 nF
LNB
Voltage
Control
DAC
Wave
Shape
Linear
Stage
VOUT
LNB
TCAP
EXTM
SDA
SCL
fsw
D2
TGate
C8
100 nF
C10
220 nF
C9
10 nF
D4
A
Fault Monitor
I 2 C™Compatible
Interface
OCP
PNG
TSD
VUV
Clock
Divider 22 kHz
TCAP
C7
22 nF
Oscillator
ADD
TDO
IRQ
PAD
For recommended external components, refer to table 7
8294-DS, Rev. 5
GND
Tone
Detect
TDI
C10
R8
100 7 10 nF
A
D3 and D4 are used for surge protection.
A8294
Single LNB Supply and Control Voltage Regulator
Description (continued)
The device uses a 2-wire bidirectional serial interface, compatible
with the I2C™ standard, that operates up to 400 kHz.
The A8294 is supplied in a lead (Pb) free MLP/QFN package,
ES, 20-contact, 4 mm × 4 mm, 0.75 nominal overall height.
Selection Guide
Part Number
Packinga
Description
A8294SESTR-Tb
7 in. reel, 1500 pieces/reel
12 mm carrier tape
ES package, MLP/QFN surface mount
4 mm × 4 mm × 0.75 mm nominal height
aContact Allegro
bLeadframe
for additional packing options.
plating 100% matte tin.
Absolute Maximum Ratings
Rating
Units
Load Supply Voltage, VIN pin
Characteristic
Symbol
VIN
Conditions
30
V
Output Current1
IOUT
Internally
Limited
A
–0.3 to 33
V
–1 to 33
V
–0.3 to 30
V
–0.3 to 41
V
Logic Input Voltage, EXTM pin
–0.3 to 5
V
Logic Input Voltage, other pins
–0.3 to 7
V
Logic Output Voltage
–0.3 to 7
V
Output Voltage, BOOST pin
Surge2
Output Voltage, LNB pin
Output Voltage, LX pin
Output Voltage, VCP pin
VCP
Operating Ambient Temperature
TA
–20 to 85
°C
Junction Temperature
TJ(max)
150
°C
Storage Temperature
Tstg
–55 to 150
°C
1Output
current rating may be limited by duty cycle, ambient temperature, and heat sinking. Under any set of conditions, do not exceed the specified current ratings, or a junction temperature, TJ, of 150°C.
2Use Allegro recommended Application circuit.
Thermal Characteristics may require derating at maximum conditions, see application information
Characteristic
Package Thermal Resistance
Test Conditions*
Symbol
RθJA
On 4-layer PCB based on JEDEC standard
Value
Unit
37
ºC/W
*Additional thermal information available on the Allegro website
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
A8294
Single LNB Supply and Control Voltage Regulator
16 NC
17 VIN
18 LX
19 GND
20 LNB
Device Pin-out Diagram
BOOST
1
15
FLOAT
VCP
2
14
GND
TCAP
3
13
NC
FLOAT
4
12
SCL
EXTM
5
11
IRQ
8
VREG
ADD 10
7
SDA 9
6
TDI
GND
PAD
(Top View)
Terminal List Table
Name
Number
Function
ES
ADD
10
Address select
FLOAT
4, 15
BOOST
1
These pins must not be connected to anything; do not ground these pins
Tracking supply voltage to linear regulator
EXTM
5
External modulation input
GND
7, 14
GNDLX
19
Signal ground
Boost switch ground
IRQ
11
Interrupt request
LNB
20
Output voltage to LNB
LX
18
NC
13, 16
Inductor drive point
PAD
Pad
SCL
12
I2C™-compatible clock input
SDA
9
I2C™-compatible data input/output
TCAP
3
Capacitor for setting the rise and fall time of the LNB output
TDI
6
Outgoing Tone Detect Feedback (for verification)
VCP
2
Gate supply voltage
VIN
17
Supply input voltage
VREG
8
Analog supply
No connection
Exposed pad; connect to the ground plane, for thermal dissipation
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
A8294
Single LNB Supply and Control Voltage Regulator
ELECTRICAL CHARACTERISTICS at TA = 25°C, VIN = 10 to 16 V, unless noted otherwise1
Characteristics
Symbol
Test Conditions
Min.
Typ.
Max.
Units
–3.0
–
3.0
%
General
Set-Point Accuracy, Load and Line Regulation2
Supply Current
Boost Switch On Resistance
Err
IIN(Off)
ENB bit = 0, LNB output disabled, VIN = 12 V
–
–
10.0
mA
IIN(On)
ENB bit = 1, LNB output enabled,
ILOAD = 0 mA, VIN = 12 V
–
–
19.0
mA
RDS(on)BOOST ILOAD = 450 mA
–
300
–
mΩ
320
352
384
kHz
VOUT = 19.0 V
–
2.7
–
A
∆VREG
VBOOST – VLNB, no tone signal,
ILOAD = 450 mA
–
800
–
mV
ICHG
TCAP capacitor (C7) charging
–12.5
–10
–7.5
μA
7.5
10
12.5
μA
Switching Frequency
fSW
Switch Current Limit
ILIMSW
Linear Regulator Voltage Drop
TCAP Pin Current
Relative to selected VLNB target level,
ILOAD = 0 to 450 mA
IDISCHG
TCAP capacitor (C7) discharging
Output Voltage Rise Time3
tr(VLNB)
For VLNB 13 → 18 V; CTCAP = 5.6 nF,
ILOAD = 450 mA
–
500
–
μs
Output Voltage Pull-Down Time3
tf(VLNB)
For VLNB 18 → 13 V; CLOAD = 100 μF,
ILOAD = 0 mA
–
12.5
–
ms
IRLNB
ENB bit = 0, VLNB = 33 V , BOOST capacitor
(C5) fully charged
–
1
5
mA
Vrip,n(pp)
20 MHz BWL; reference circuit shown in
Functional Block diagram; contact Allegro for
additional information on application circuit
board design
–
30
–
mVPP
ILIMLNB
VBOOST – VLNB = 800 mV
800
850
950
mA
–
48
–
ms
VUVLO
VIN falling
7.05
7.35
7.65
V
VIN(th)
VIN rising
Output Reverse Current
Ripple and Noise on LNB
Output4
Protection Circuitry
Output Overcurrent Limit5
Overcurrent Disable Time
tDIS
VIN Undervoltage Lockout Threshold
VIN Turn On Threshold
7.40
7.70
8.00
V
VUVLOHYS
–
350
–
mV
Thermal Shutdown Threshold3
TJ
–
165
–
°C
Thermal Shutdown Hysteresis3
∆TJ
–
20
–
°C
Undervoltage Hysteresis
Power Not Good Flag Set
PNGSET
Power Not Good Flag Reset
Power Not Good Hysteresis
With respect to VLNB
77
85
93
%
PNGRESET With respect to VLNB
82
90
98
%
With respect to VLNB
–
5
–
%
20
22
24
kHz
PNGHYS
Tone
Tone Frequency
fTONE
Tone Amplitude, Peak-to-Peak
VTONE(pp)
ILOAD = 0 to 450 mA, CLOAD = 750 nF
400
620
900
mV
Tone Duty Cycle
DCTONE
ILOAD = 0 to 450 mA, CLOAD = 750 nF
40
50
60
%
Tone Rise Time
trTONE
ILOAD = 0 to 450 mA, CLOAD = 750 nF
5
10
15
μs
Tone Fall Time
tfTONE
ILOAD = 0 to 450 mA, CLOAD = 750 nF
5
10
15
μs
fTONE = 22 kHz sine wave, using internal tone
400
–
–
mV
600 mVpp sine wave
20
–
24
kHz
Outgoing Tone Detection
Outgoing Tone Amplitude, Peak to Peak3
Outgoing Tone Frequency
Capture3
VTDT(pp)init
fTDI
Continued on the next page…
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
A8294
Single LNB Supply and Control Voltage Regulator
ELECTRICAL CHARACTERISTICS (continued) at TA = 25°C, VIN = 10 to 16 V, unless noted otherwise1
Characteristics
Symbol
Test Conditions
Min.
Typ.
Max.
Units
I2C™-Compatible Interface
Logic Input (SDA,SCL) Low Level
VSCL(L)
–
–
0.8
V
Logic Input (SDA,SCL) High Level
VSCL(H)
2.0
–
–
V
Logic Input Hysteresis
VI2CIHYS
Logic Input Current
II2CI
Logic Output Voltage SDA and IRQ
Vt2COut(L)
Logic Output Leakage SDA and IRQ
Vt2CLKG
SCL Clock Frequency
VI2CI = 0 to 7 V
ILOAD = 3 mA
Vt2COut = 0 to 7 V
fCLK
Output Fall Time
tfI2COut
150
–
mV
<±1.0
10
μA
–
–
0.4
V
–
–
10
μA
–
–
400
kHz
–
–
250
ns
tBUF
1.3
–
–
μs
Hold Time Start Condition
tHD:STA
0.6
–
–
μs
Setup Time for Start Condition
tSU:STA
0.6
–
–
μs
SCL Low Time
tLOW
1.3
–
–
μs
SCL High Time
tHIGH
0.6
–
–
μs
100
–
–
ns
0
–
900
ns
0.6
–
–
μs
Bus Free Time Between Stop/Start
Data Setup Time
Vt2COut(H) to Vt2COut(L)
–
–10
tSU:DAT
Data Hold Time
tHD:DAT
Setup Time for Stop Condition
tSU:STO
For tHD:DAT(min) , the master device must
provide a hold time of at least 300 ns for the
SDA signal in order to bridge the undefined
region of the SCL signal falling edge
I2C™ Address Setting
ADD Voltage for Address 0001,000
Address1
0
–
0.7
V
ADD Voltage for Address 0001,001
Address2
1.3
–
1.7
V
ADD Voltage for Address 0001,010
Address3
2.3
–
2.7
V
ADD Voltage for Address 0001,011
Address4
3.3
–
5.0
V
1Operation
at 16 V may be limited by power loss in the linear regulator.
the selected VLNB target level 13.375 V, Err(min) = –3.7%.
3Guaranteed by worst case process simulations and system characterization.
4LNB output ripple and noise are dependent on component selection and PCB layout. Refer to the Application Schematic and PCB layout
recommendations. Not production tested.
5Current from the LNB output may be limited by the choice of Boost components.
2For
I2C™ Interface Timing Diagram
tSU:STA
tHD:STA
tSU:DAT
tHD:DAT
tSU:STO
tBUF
SDA
SCL
tLOW
tHIGH
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
A8294
Single LNB Supply and Control Voltage Regulator
Functional Description
Protection
The A8294 has a wide range of protection features and fault diagnostics which are detailed in the Status Register section.
Boost Converter/Linear Regulator
The A8294 solution contains a tracking current-mode boost
converter and linear regulator. The boost converter tracks the
requested LNB voltage to within 800 mV, to minimize power
dissipation. Under conditions where the input voltage, VBOOST ,
is greater than the output voltage, VLNB, the linear regulator must
drop the differential voltage. When operating in these conditions,
care must be taken to ensure that the safe operating temperature
range of the A8294 is not exceeded.
The boost converter operates at 352 kHz typical: 16 times
the internal 22 kHz tone frequency. All the loop compensation,
current sensing, and slope compensation functions are provided
internally.
The A8294 has internal pulse-by-pulse current limiting on
the boost converter and DC current limiting on the LNB output
to protect the IC against short circuits. When the LNB output is
shorted, the LNB output current is limited to 700 mA typical,
and the IC will be shut down if the overcurrent condition lasts
for more than 48 ms. If this occurs, the A8294 must be reenabled
for normal operation. The system should provide sufficient time
between successive restarts to limit internal power dissipation; a
minimum of 2 s is recommended.
At extremely light loads, the boost converter operates in a
pulse-skipping mode. Pulse skipping occurs when the BOOST
voltage rises to approximately 450 mV above the BOOST target
output voltage. Pulse skipping stops when the BOOST voltage
drops 200 mV below the pulse skipping level.
In the case that two or more set top box LNB outputs are connected together by the customer (e.g., with a splitter), it is possible that one output could be programmed at a higher voltage
than the other. This would cause a voltage on one output that is
higher than its programmed voltage (e.g., 19 V on the output of a
13 V programmed voltage). The output with the highest voltage
will effectively turn off the other outputs. As soon as this voltage
is reduced below the value of the other outputs, the A8294 output
will auto-recover to their programmed levels.
Charge Pump. Generates a supply voltage above the internal
and fall times can be set by the value of the capacitor connected
from the TCAP pin to GND (CTCAP or C7 in the Applications
Schematic). Note that during start-up, the BOOST pin is precharged to the input voltage minus a voltage drop. As a result,
the slew rate control for the BOOST pin occurs from this voltage.
The value of CTCAP can be calculated using the following formula:
CTCAP = (ITCAP × 6) / SR ,
where SR is the required slew rate of the LNB output voltage,
in V/s, and ITCAP is the TCAP pin current specified in the data
sheet. The recommended value for CTCAP, 10 nF, should provide
satisfactory operation for most applications. However, in some
cases, it may be necessary to increase the value of CTCAP to avoid
activating the current limit of the LNB output. One such situation is when two set-top boxes are connected in parallel. If this is
the case, the following formula can be used to calculate CTCAP:
CTCAP ≥ (ITCAP × 6)(2 × CBOOST) / ILIMLNB ,
CTCAP ≥ (10 μA × 6)(2 × 100 μF) / 500 mA = 24 nF .
The minimum value of CTCAP is 2.2 nF. There is no theoretical
maximum value of CTCAP however too large a value will probably cause the voltage transition specification to be exceeded.
Tone generation is unaffected by the value of CTCAP .
Pull-Down Rate Control. In applications that have to operate at
very light loads and that require large load capacitances (in the
order of tens to hundreds of microfarads), the output linear stage
provides approximately 40 mA of pull-down capability. This
ensures that the output volts are ramped from 18 V to 13 V in a
reasonable amount of time.
ODT (Overcurrent Disable Time)
If the LNB output current exceeds 850 mA, typical, for more than
48 ms, then the LNB output will be disabled and the OCP bit will
be set.
Short Circuit Handling
If the LNB output is shorted to ground, the LNB output current
will be clamped to 850 mA, typical. If the short circuit condition
lasts for more than 48 ms, the A8294 will be disabled and the
OCP bit will be set.
tracking regulator output to drive the linear regulator control.
Auto-Restart
Slew Rate Control. During either start-up, or when the output
After a short circuit condition occurs, the host controller should
periodically reenable the A8294 to check if the short circuit has
voltage at the LNB pin is transitioning, the output voltage rise
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
6
A8294
Single LNB Supply and Control Voltage Regulator
been removed. Consecutive startup attempts should allow at least
2 s of delay between restarts.
In-Rush Current
At start-up or during an LNB reconfiguration event, a transient surge current above the normal DC operating level can
be provided by the A8294. This current increase can be as high
as 850 mA, typical, for as long as required, up to a maximum
of 48 ms.
Tone Generation
The A8294 solution offers two options for tone generation. The
EXTM pin (external modulation), in conjunction with the I2C™
control bit, TMODE (tone mode), provides the necessary control.
Both the EXTM pin and TMODE bit determine the 22 kHz control, whether external or internal. With either of the two options,
when a tone signal is generated TDET is set in the status register,
with the minimum tone detect amplitude of 400 mV.
The two options for tone generation are shown in figure 1.
EXTM
TMODE
TGATE
Tone
(LNB Ref)
LNB (V)
Option 1 – Use external modulation via the EXTM pin
EXTM
TMODE
TGATE
Tone
(LNB Ref)
LNB (V)
Option 2 – Use internal modulation by 22-kHz internal clock
Figure 1. Options for tone generation
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
7
A8294
Single LNB Supply and Control Voltage Regulator
The address is transmitted MSB first.
3. Data Cycles.
Write – 6 bits of data and 2 bits for addressing four internal
control registers, followed by an acknowledge bit. See Control
Register section for more information.
Read – Two status registers, where register 1 is read first,
followed by register 2, then register 1, and so on. At the start
of any read sequence, register 1 is always read first. Data is
transmitted MSB first.
4. Stop Condition. Defined by a positive edge on the SDA line,
while SCL is high. Except to indicate a Start or Stop condition, SDA must be stable while the clock is high. SDA can
only be changed while SCL is low. It is possible for the Start or
Stop condition to occur at any time during a data transfer. The
A8294 always responds by resetting the data transfer sequence.
I2C™-Compatible Interface
This is a serial interface that uses two bus lines, SCL and SDA,
to access the internal Control and Status registers of the A8294.
Data is exchanged between a microcontroller (master) and the
A8294 (slave). The clock input to SCL is generated by the master,
while SDA functions as either an input or an open drain output,
depending on the direction of the data.
Timing Considerations
The control sequence of the communication through the I2C™compatible interface is composed of several steps in sequence:
1. Start Condition. Defined by a negative edge on the SDA line,
while SCL is high.
2. Address Cycle. 7 bits of address, plus 1 bit to indicate read (1)
or write (0), and an acknowledge bit. The first five bits of the
address are fixed as: 00010. The four optional addresses, defined by the remaining two bits, are selected by the ADD input.
The Read/Write bit is used to determine the data transfer direction. If the Read/Write bit is high, the master reads the contents of
register 1, followed by register 2 if a further read is performed. If
acknowledge
from LNBR
Start
Address
acknowledge
from LNBR
W
Control Data
SDA
0
0
0
1
0
A1
A0
0
AK
SCL
1
2
3
4
5
6
7
8
9
I1
I0
D5
D4
D3
Stop
D2
D1
D0
AK
Write to Register
acknowledge
from LNBR
Start
Address
no acknowledge
from master
R
Status Register 1
SDA
0
0
0
1
0
A1
A0
1
AK
SCL
1
2
3
4
5
6
7
8
9
D7
D6
D5
D4
D3
D2
Stop
D1
D0 NAK
Read One Byte from Register
acknowledge
from LNBR
Start
Address
R
acknowledge
from LNBR
Status Data in Register 1
SDA
0
0
0
1
0
A1
A0
1
AK
SCL
1
2
3
4
5
6
7
8
9
D7
D6
D5
D4
D3
D2
D1
no acknowledge
from master
Status Data in Register 2
D0
AK
-
-
-
-
D3
D2
D1
Stop
D0 NAK
Read Multiple Bytes from Register
Figure 2. I2C™ Interface. Read and write sequences.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
8
A8294
Single LNB Supply and Control Voltage Regulator
the Read/Write bit is low, the master writes data to one of the two
Control registers. Note that multiple writes are not permitted. All
write operations must be preceded with the address.
The Acknowledge bit has two functions. It is used by the master to determine if the slave device is responding to its address
and data, and it is used by the slave when the master is reading
data back from the slave. When the A8294 decodes the 7-bit address field as a valid address, it responds by pulling SDA low
during the ninth clock cycle.
During a data write from the master, the A8294 also pulls SDA
low during the clock cycle that follows the data byte, in order to
indicate that the data has been successfully received. In both cases, the master device must release the SDA line before the ninth
clock cycle, in order to allow this handshaking to occur.
During a data read, the A8294 acknowledges the address in the
same way as in the data write sequence, and then retains control
of the SDA line and send the data from register 1 to the master.
On completion of the eight data bits, the A8294 releases the SDA
line before the ninth clock cycle, in order to allow the master to
acknowledge the data. If the master holds the SDA line low during this Acknowledge bit, the A8294 responds by sending the
data from register 2 to the master. Data bytes continue to be sent
to the master until the master releases the SDA line during the
Acknowledge bit. When this is detected, the A8294 stops sending
data and waits for a stop signal.
Interrupt Request
The A8294 also provides an interrupt request pin, IRQ, which
is an open-drain, active-low output. This output may be connected to a common IRQ line with a suitable external pull-up and can
be used with other I2C™-compatible devices to request attention
Start
Address
from the master controller.
The IRQ output becomes active when either the A8294 first
recognizes a fault condition, or at power-on, when the main supply, VIN , and the internal logic supply, VREG , reach the correct
operating conditions. It is only reset to inactive when the I2C™
master addresses the A8294 with the Read/Write bit set (causing a read). Fault conditions are indicated by the TSD, VUV, and
OCP bits, and are latched in the Status register. See the Status
register section for full description.
The DIS and PNG status bits do not cause an interrupt. The
PNG bit is continually updated, apart from the DIS bit, which
changes when the LNB is either disabled, faulted, or is enabled.
When the master recognizes an interrupt, it addresses all
slaves connected to the interrupt line in sequence, and then reads
the status register to determine which device is requesting attention. The A8294 latches all conditions in the Status register until
the completion of the data read. The action at the resampling
point is further defined in the Status Register section. The bits in
the Status register are defined such that the all-zero condition indicates that the A8294 is fully active with no fault conditions.
When VIN is initially applied, the I2C™-compatible interface
does not respond to any requests until the internal logic supply
VREG has reached its operating level. Once VREG has reached this
point, the IRQ output goes active, and the VUV bit is set. After
the A8294 acknowledges the address, the IRQ flag is reset. After
the master reads the status registers, the registers are updated with
the VUV reset.
R
Status Register 1
SDA
0
0
0
1
0
A1
A0
1
AK
SCL
1
2
3
4
5
6
7
8
9
D7
D6
D5
D4
D3
D2
Stop
D1
D0 NAK
IRQ
Fault
Event
Read after Interrupt
Reload
Status Register
Figure 3. I2C™ Interface. Read sequences after interrupt request.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
9
A8294
Single LNB Supply and Control Voltage Regulator
Control Registers (I2C™-Compatible Write Register)
All main functions of the A8294 are controlled through the I2C™compatible interface via the 8-bit Control registers. As the A8294
contains numerous control options, it is necessary to have two
control registers. Each register contains up to 6 bits of data (bit
0 to bit 5), followed by 2 bits for the register address (bit 6 and
bit 7). The power-up states for the control functions are all 0s.
The following tables define the control bits for each address
and the settings for output voltage:
Table 1. Control Register Address (I1, I0) = 00
Bit 0
Bit 1
Bit 2
VSEL0
VSEL1
VSEL2
Bit 3
VSEL3
Bit 4
Bit 5
ODT
ENB
Bit 6
Bit 7
I0
I1
Bit
Name
Function
0
VSEL0
1
VSEL1
2
VSEL2
3
VSEL3
4
ODT
5
ENB
6
I0
Address Bit: 0
7
I1
Address Bit: 0
See table 3, Output Voltage Amplitude Selection
0: LNB = Low range
1: LNB = High range
1 (recommended): The ODT functions are always
enabled, but setting 1 recommended at all times.
0: Disable LNB Output
1: Enable LNB Output
These three bits provide incremental control over the voltage on the LNB output.
The available voltages provide the necessary levels for all the common standards
plus the ability to add line compensation in increments of 333 mV. The voltage
levels are defined in table 3, Output Voltage Amplitude Selection.
Switches between the low level and high level output voltages on the LNB output.
0 selects the low level voltage and 1 selects the high level. The low-level center voltage
is 12.709 V nominal and the high level is 18.042 V nominal. These may be increased
in steps of 333 mV using the VSEL2, VSEL1 and VSEL0 control register bits.
The overcurrent disable timer is always enabled.
Enables the LNB output. When set to 1 the LNB output is switched on. When set to
0, the LNB output is disabled.
Address
Address
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
10
A8294
Single LNB Supply and Control Voltage Regulator
Table 2. Control Register Address (I1, I0) = 10
Bit
Name
Function
0
TMODE
1
TGATE
2
-
Not Used (0 recommended)
3
-
Not Used
4
-
Not Used
5
-
Not Used
6
I0
Address Bit: 0
7
I1
Address Bit: 1
0: Enable external tone modulation via EXTM pin
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
1: Enable internal clock modulation of tone, with
gating via EXTM pin
Must be set to 1: Tone Ready
TMODE Tone Mode. Selects source of tone frequency generation. When set to 0, a digital
pulse signal on the EXTM pin is used. When set to 1, a 22-kHz internal clock signal
is used. In the case where the the internal clock is used, set the EXTM pin high to
enable modulation, and set it low to disable modulation. See Tone Generation Section for more information.
TGATE Tone Ready. Must be set to 1.
–
Not Used.
–
Not Used.
–
Not Used.
–
Not Used.
I0
Address.
I1
Address.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
11
A8294
Single LNB Supply and Control Voltage Regulator
Table 3. Output Voltage Amplitude Selection
VSEL3x
VSEL2x
VSEL1x
VSEL0x
LNB (V)
0
0
0
1
13.042
0
0
1
0
13.375
0
0
1
1
13.709
1
0
0
1
18.375
1
0
1
0
18.709
1
0
1
1
19.042
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
12
A8294
Single LNB Supply and Control Voltage Regulator
Status Registers (I2C™-Compatible Read Register)
The main fault conditions: overcurrent (OCP), under voltage
(VUV) and overtemperature (TSD), are all indicated by setting
the relevant bits in the Status registers. In all fault cases, once the
bit is set, it remains latched until the A8294 is read by the I2C™
master, assuming the fault has been resolved.
The current status of the LNB output is indicated by the disable bit, DIS. The DIS bit is set when either a fault occurs or if
the LNB is disabled intentionally. This bit is latched, and is reset
when the LNB is commanded on again. The power not good
(PNG) and outgoing tone detect (TDET) are the only bits which
may be reset without an I2C™ read sequence. Table 4 summarizes
the condition of each bit when set and how it is reset.
As the A8294 has a comprehensive set of status reporting bits,
it is necessary to have two Status registers. When performing a
multiple read function, register 1 is read followed by register 2,
then register 1 again and so on. Whenever a new read function is
performed, register 1 is always read first.
The normal sequence of the master in a fault condition will be
to detect the fault by reading the Status registers, then rereading
the Status registers until the status bit is reset indicating the fault
condition is reset. The fault may be detected either by continuously
polling, by responding to an interrupt request (IRQ), or by detecting a fault condition externally and performing a diagnostic poll of
all slave devices. Note that the fully-operational condition of the
Status registers is all 0s, to simplify checking of the Status bit.
Table 4. Status Register Bit Setting
Status Bit
–
Function
Not used
Reset
Condition
Set
–
Not used
DIS
LNB disabled, either intentionally or
due to fault
Latched
LNB enabled and no fault
OCP
Overcurrent
Latched
I2C™ read and fault removed
PNG
Power not good
Non-latched
TDET
Outgoing tone detect
Non-latched
TSD
Thermal shutdown
Latched
I2C™ read and fault removed
VUV
Undervoltage
Latched
I2C™ read and fault removed
LNB volts in range
Tone stopped
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
13
A8294
Single LNB Supply and Control Voltage Regulator
Table 5. Status Register 1
Bit 0
DIS
Bit 1
Bit 2
–
OCP
Bit 3
Bit 4
–
PNG
Bit 5
Bit 6
–
TSD
Bit 7
VUV
Bit
Name
Function
0
DIS
LNB output disabled
1
–
Not Used
2
OCP
Overcurrent
3
–
Not Used
4
PNG
Power Not Good
5
–
Not Used
6
TSD
Thermal Shutdown
7
VUV
VIN Undervoltage
LNB Output Disabled. DIS is used to indicate the current condition of the LNB
output. At power-on, or if a fault condition occurs, DIS will be set. This bit changing
to 1 does not cause the IRQ to activate because the LNB output may be disabled intentionally by the I2C™ master. This bit will be reset at the end of a write sequence
if the LNB output is enabled.
Not used.
Overcurrent. If the LNB output detects an overcurrent condition, for greater than
48 ms, the LNB output will be disabled. The OCP bit will be set to indicate that an
overcurrent has occurred and the disable bit, DIS, will be set. The Status register is
updated on the rising edge of the 9th clock pulse in the data read sequence, where the
OCP bit is reset in all cases, allowing the master to reenable the LNB output.
If the overcurrent timer is not enabled, the device operate in current limit indefinitely
and the OCP bit will be set. If the overcurrent condition is removed, the OCP bit will
automatically be reset. Note that if the overcurrent operates long enough, and a thermal shutdown occurs, the LNB output will be disabled and the TSD bit will be set.
Not used.
Power Not Good. Set to 1 when the LNB output is enabled and the LNB voltage is
below 85% of the programmed voltage. The PNG is reset when the LNB volts are
within 90% of the programmed LNB voltage.
Not used.
Thermal shutdown. 1 indicates that the A8294 has detected an overtemperature
condition and has disabled the LNB output. The disable bit, DIS, will also be set.
The status of the overtemperature condition is sampled on the rising edge of the 9th
clock pulse in the data read sequence. If the condition is no longer present, then the
TSD bit will be reset, allowing the master to reenable the LNB output if required. If
the condition is still present, then the TSD bit will remain at 1.
Undervoltage Lockout. 1 indicates that the A8294 has detected that the input supply, VIN is, or has been, below the minimum level and an undervoltage lockout has
occurred disabling the LNB outputs. The disable bit, DIS, will also be set and the
A8294 will not reenable the output until so instructed by writing the relevant bit into
the control registers. The status of the undervoltage condition is sampled on the rising
edge of the 9th clock pulse in the data read sequence. If the condition is no longer
present, then the VUV bit will be reset allowing the master to reenable the LNB output if required. If the condition is still present, then the VUV bit will remain at 1.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
14
A8294
Single LNB Supply and Control Voltage Regulator
Table 6. Status Register 2
Bit 0
Bit 1
Bit 2
–
–
TDET
Bits 3 to 7
Bit
Name
Function
0
–
Not Used
1
–
Not Used
2
TDET
Outgoing Tone Detect
3
–
Not Used
4
–
Not Used
5
–
Not Used
6
–
Not Used
7
–
Not Used
Not used.
Not used.
Outgoing Tone Detect. When tone is enabled, TDET will be set to 1 if the tone appears at the LNB output. When the tone is disabled, TDET is reset.
Not used.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
15
A8294
Single LNB Supply and Control Voltage Regulator
Table 7. Component Selection Table
Component
C1, C4, C8
C2, C5
Characteristics
Manufacturer Device
100 nF, 50 V, X5R or X7R, 0603
100 μF, 35 VMIN , ESR < 75 mΩ, IRIPPLE > 800 mA
C3
220 nF, 10 VMIN, X5R or X7R, 0402 or 0603
C6
1.0 μF, 25 VMIN, X5R or X7R, 1206
C7
22 nF, 10 VMIN, X5R or X7R, 0402 or 0603
C9
10 nF, 50 V, X5R or X7R, 0402 or 0603
C10
220 nF, 50 V, X5R or X7R, 0805
Panasonic: EEU-FM1H101B
ChemiCon: EKZE500ELL101MHB5D
Nichicon: UHC1V101MPT
Panasonic: EEU-FM1H101B
TDK: C3216X7R1E105K
Murata: GRM31MR71E105KA01
Taiyo Yuden: TMK316BJ105KL-T
Kemet: C1206C105K3RACTU
Schottky diode, 40 V, 1 A, SOD-123
Diodes, Inc: B140HW-7
Central Semi: CMMSH1-40
D3
Schottky diode, 40 V, 3 A, SMA
Sanken: SFPB-74
Vishay: B340A-E3/5AT
Diodes, Inc.: B340A-13-F
Central Senmi: CMSH3-40MA
D4
TVS, 20 VRM, 32 VCL at 500 A (8/20 μs), 3000 W
ST:LNBTVS6-221S
Littelfuse: SMDJ20A
L1
33 H, ISAT > 2.6 A, DCR < 90 mΩ
TDK: TSL1112RA-330K2R3-PF
Taiyo Yuden: LHLC10TB330K
Coilcraft: DR0810-333L
D1, D2
R1 to R4
Determined by VDD, bus capacitance, etc.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
16
A8294
Single LNB Supply and Control Voltage Regulator
Package ES 20-Pin MLP/QFN
0.30
4.00 ±0.10
1
2
0.50
20
20
0.95
A
1
2
4.00 ±0.10
2.45
4.10
2.45
4.10
21X
D
SEATING
PLANE
0.08 C
+0.05
0.25 –0.07
0.75 ±0.05
0.50
C
C
PCB Layout Reference View
For Reference Only, not for tooling use (reference DWG-2864, JEDEC MO-220 WGGD)
Dimensions in millimeters
Exact case and lead configuration at supplier discretion within limits shown
A Terminal #1 mark area
B Exposed thermal pad (reference only, terminal #1
identifier appearance at supplier discretion)
0.40 ±0.10
B
2.45
2
1
C Reference land pattern layout (reference IPC7351
QFN50P400X400X80-21BM)
All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary
to meet application process requirements and PCB layout tolerances; when
mounting on a multilayer PCB, thermal vias at the exposed thermal pad land
can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5)
D Coplanarity includes exposed thermal pad and terminals
20
2.45
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
17
A8294
Single LNB Supply and Control Voltage Regulator
I2C™ is a trademark of Philips Semiconductors.
DiSEqC™ is a trademark of Eutelsat S.A.
Copyright ©2007-2013, Allegro MicroSystems, LLC
Allegro MicroSystems, LLC reserves the right to make, from time to time, such departures from the detail specifications as may be required to
permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that
the information being relied upon is current.
Allegro’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the
failure of that life support device or system, or to affect the safety or effectiveness of that device or system.
The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, LLC assumes no responsibility for its
use; nor for any infringement of patents or other rights of third parties which may result from its use.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
18
Similar pages