Highest Power Density, Multirail Power Solution for Space-Constrained...

Highest Power Density,
Multirail Power Solution
for Space-Constrained
Applications
sequencing is critical to ensure that the FPGA is up and running
before the memory is enabled. Regulators with a precision enable
input and a dedicated power-good output allow power supply
sequencing and fault monitoring. Power supply designers often
want to use the same power IC in different applications, so the
ability to change the current limits is important. This design reuse
can significantly reduce time to market—a critical element in any
new product development process.
4.5V TO 15V
INPUT VOLTAGE
4A BUCK
REGULATOR
4A BUCK
REGULATOR
As the overall size of communications, medical, and industrial
equipment continues to decrease, power management becomes an
increasingly important design consideration. This article looks at
applications for new highly integrated power management solutions,
the advantages these new devices bring for powering RF systems,
FPGAs, and processors, and a design tool that helps empower
designers to quickly implement a new design.
The emergence of femtocells and picocells in communications
infrastructure is driving the need for smaller base stations, which
have complex requirements for powering digital baseband, memory,
RF transceivers, and power amplifiers in the smallest area with
the highest power efficiency, as shown in Figure 1. A typical small
cell system needs a very dense power supply that can deliver large
currents with fast transient response to power the digital baseband,
along with low-noise, low-dropout regulators (LDOs) to power
the AD9361 RF Agile Transceiver,™ temperature compensated
crystal oscillator (TCXO), and other noise-critical rails. Setting the
switching frequency of the switching regulators outside of the critical
RF bands reduces noise, and synchronizing the switching regulators
ensures that beat frequencies do not affect the RF performance.
Reducing the core voltage (VCORE) of the digital baseband minimizes
power consumption for low-power modes, and supply sequencing
ensures that the digital baseband processor is up and running before
the RF transceiver is enabled. An I2C interface between the digital
baseband and the power management allows the output voltages of
the buck regulators to be changed. To increase reliability, the power
management system can monitor its own input voltage and die
temperature, reporting any faults to the baseband processor.
12V INPUT
[email protected]
4A BUCK
REGULATOR
4A BUCK
REGULATOR
ADP5050/
ADP5052
1.2A BUCK
REGULATOR
200mA LDO
DUAL
FETS
[email protected]
VCORE
VDDIO
ADP1741
2.5V/4A
VCCAUX
VCCO_0, 1, 2
1.5V/1.2A
1.2A BUCK
REGULATOR
VCC0_3
1.2A BUCK
REGULATOR
2.5V
CORE
VOLTAGE
FPGA
AUXILIARY
VOLTAGE
BANK 0
I/Os BANK 1
BANK 2
I/Os BANK 3
DDR
TERM. LDO
0.75V
VPLL
DDR3
MEMORY
FLASH
MEMORY
3.3V/1.2A
1.2V/100mA
200mA LDO
PWRGD
Figure 2. Powering an FPGA-based system.
Consider a common multirail power management design
specification for an FPGA with a 12-V input and five outputs:
•Core: 1.2 V @ 4 A
•Auxiliary: 1.8 V @ 4 A
•I/O: 3.3 V @ 1.2 A
•DDR memory: 1.5 V @ 1.2 A
•Clock: 1.0 V @ 200 mA
A typical discrete implementation, shown in Figure 3a, connects
four switching regulators to the 12-V input rail. The output of
one switching regulator preregulates the LDO to reduce power
dissipation. An alternative approach, shown in Figure 3b, uses
one regulator to step the 12-V input down to a 5-V intermediate
rail, which is then regulated down to produce each of the required
voltages. This implementation has a lower solution cost, but also
a lower efficiency due to the two-stage power conversion. In both
cases, each regulator has to be enabled independently, so supply
sequencing may require a dedicated power supply sequencer.
Noise may also be an issue, unless all of the switchers can be
synchronized to reduce beat frequencies.
VDD_1V3
VDD_INTERFACE
[email protected]
VDD_GPO
ADM7160
1.2A BUCK
REGULATOR
VCCINT
DDR3
PWRGD
[email protected]
DIGITAL BASEBAND
1.2V/4A
FETS
By Maurice O’Brien
RF
TRANSCEIVER
AD9361
TCXO
12VIN
PA
[email protected]
(a)
BUCK 1
REG
1.2V @ 4A (CORE RAIL)
BUCK 2
REG
1.8V @ 4A (AUX RAIL)
BUCK 3
REG
3.3V @ 1.2A (I/O RAIL)
BUCK 4
REG
1.5V @ 1.2A (DDR MEMORY RAIL)
1V @ 200mA (CLOCKING/MGT RAIL)
LDO 1
Figure 1. Small base stations require a variety
of power supplies.
Similarly, the trend in medical and instrumentation devices—for
example, portable ultrasound and handheld instrumentation—is
toward significantly smaller form factors, so these products are
driving the need for smaller, more efficient ways of powering
FPGAs, processors, and memory, as shown in Figure 2. A typical
FPGA and memory design needs a very dense power supply that
can deliver large currents with fast transient response to power the
core and I/O rails, along with a low-noise rail to power on-chip
analog circuitry such as a phase-locked loop (PLL). Power supply
Analog Dialogue 47-11, November (2013)
12VIN
BUCK 1
REG
5V
1.2V @ 4A (CORE RAIL)
BUCK 3
REG
1.8V @ 4A (AUX RAIL)
BUCK 4
REG
3.3V @ 1.2A (I/O RAIL)
BUCK 5
REG
1.5V @ 1.2A (DDR MEMORY RAIL)
LDO 1
(b)
BUCK 2
REG
1V @ 200mA (CLOCKING/MGT RAIL)
Figure 3. (a) Discrete regulator design and
(b) alternative discrete regulator design.
www.analog.com/analogdialogue
1
Integrated Solution Yields High Efficiency, Small Size
FREQUENCY (Hz)
1.2M
VOUT5
7
FB5
ADP5050
7mm × 7mm
DL1
31
PGND
30
8
PVIN5
DL2
29
9
PVIN4
SW2
28
10
SW4
SW2
27
11
PGND4
PVIN2
26
BST4
PVIN2
25
0.47µF
6.3V/XR5
0402
SS2
FB2 COMP2 EN2
1nF
6.3V/XR5
0402
1.0µF
6.3V/XR5
0402
100kΩ
0402
BST2
24
SCL
23
15
14
1nF
6.3V/XR5
0402
nINT VDDIO SDA
80
CIN1–10F
25V/X5R
0805
D2
G2
D2
S2
LAYOUT EXAMP
VIN = 12V
BUCK 1: 3A @ 6
BUCK 2: 2A @ 1
BUCK 3: 1.2A @
BUCK 4: 0.6A @
LDO: 0.1A
100F
6.3V/XR5
1206
47kΩ
0402
DUAL NFETS
3mm × 3mm POWERPAK
D1
G1
D1
S1
47F
6.3V/XR5
1206
47kΩ
0402
CIN2–10F
25V/X5R
0805
0.47µF
6.3V/XR5
0402
100kΩ
0402
3.3H
5mm × 5mm
6
60
VOUT1
(1.2V/3A)
2.2H
4mm × 4mm
37
38
39
40
41
42
32
13
VOUT4
(5V/0.6A)
43
SW1
EN4 COMP4 FB4
COUT4–22F
6.3V/X5R
0805
44
33
EN
5
12
10H
5mm × 5mm
45
46
SW1
22
CIN4–10F
25V/X5R
0805
34
PVIN3
4
21
4.7µF
6.3V/XR5
0402
35
PVIN1
20
4.7µF
6.3V/XR5
0402
PVIN1
SW3
3
19
R1–10kΩ
0402
FB1 COMP1 EN1
PGND3
2
18
R1–10kΩ
0402
5VREG SS1
100kΩ
0402
36
17
VOUT5
(2.5V/100mA)
0.47µF
6.3V/XR5
0402
4.7µF
6.3V/XR5
0402
BST1
BST3
40
RT RESISTOR (k)
In some designs it is desirable to have both: a lower switching
frequency to provide the highest power efficiency for the higher
current rails, and a higher switching frequency to reduce inductor
size and minimize PCB area for the lower current rails. A divideby-two option on the master switching frequency allows the
ADP5050 to operate at two frequencies, as shown in Figure 5. The
switching frequency for Buck 1 and Buck 3 can be set via the I2C
port to one-half of the master switching frequency.
EN3 COMP3 FB3 SS34 PWRGD SYNC/ RT
MODE
1
20
Figure 4. Switching frequency vs. RRT.
100kΩ
0402
16
CIN3–10F
25V/X5R
0805
47
48
6.8H
5mm × 5mm
0
1nF
6.3V/XR5
0402
100kΩ
0402
0.47µF
6.3V/XR5
0402
600k
0
1nF
6.3V/XR5
0402
COUT3–22F
6.3V/X5R
0805
800k
200k
R RT = (14822/fSW)1.081, with R in kΩ and f in kHz.
VOUT3
(1.8V/1.2A)
1.0M
400k
The switching frequency, fSW, is set between 250 kHz and 1.4 MHz
by resistor R RT. The flexible switching frequency range allows
the power supply designer to optimize the design, reducing the
frequency for highest efficiency or increasing the frequency for
smallest overall size. Figure 4 shows the relationship between f SW
and R RT. The value of R RT can be calculated as
13.39
VOUT2
(3.3V/2A)
23.17
TOTAL PCB AREA AROUND 23mm × 13.5mm = 310mm2
1nF
6.3V/XR5
0402
REG SS1
37
38
FB1 COMP1 EN1
BST1
36
PVIN1
35
PVIN1
34
SW1
33
2
SW1
32
DL1
31
CIN1–10F
25V/X5R
0805
VOUT1
(1.2V/3A)
2.2H
4mm × 4mm
0.47µF
6.3V/XR5
0402
100kΩ
0402
39
40
41
1.4M
For highest efficiency, each of the buck regulators can be powered
directly from 12 V (similar to Figure 3a), removing the need for
a preregulator stage. Buck 1 and Buck 2 have programmable
current limits (4 A, 2.5 A, or 1.2 A), allowing the power supply
designer to quickly and easily change the currents for new designs
and significantly reducing the development time. The LDO can
be powered from a 1.7-V to 5.5-V supply. In this example, the
1.8-V output from one of the buck regulators powers the LDO to
provide a low-noise 1-V rail for the noise-sensitive analog circuitry.
4.7µF
6.3V/XR5
0402
0
1.6M
Integrating multiple buck regulators and LDOs into a single
package can significantly reduce the overall size of a power
management design. In addition, smart integrated solutions
provide many advantages over traditional discrete implementations.
Reducing the number of discrete components can significantly
reduce the cost, complexity, and manufacturing cost of the design.
The ADP5050 and ADP5052 integrated power management units
(PMUs) can implement all these voltages and features in a single
IC, using significantly less PCB area and fewer components.
100F
6.3V/XR5
1206
LAYOUT EXAMPLE:
VIN = 12V
BUCK 1: 3A @ 600kHz
BUCK 2: 2A @ 1.2MHz
BUCK 3: 1.2A @ 600kHz
BUCK 4: 0.6A @ 1.2MHz
LDO: 0.1A
Figure 5. The ADP5050 operates at a low switching frequency for high efficiency on
high-current rails and a high frequency for small inductor size on low-current rails.
D2
G2
D2
S2
Analog Dialogue 47-11, November (2013)
47kΩ
0402
DUAL NFETS
47F
Power Supply Sequencing
CHANNELx
As shown in Figure 6, the ADP5050 and ADP5052 have four
features that simplify power supply sequencing that is required
for applications using FPGAs and processors: precision enable
inputs, programmable soft start, a power-good output, and an
active output discharge switch.
INTERNAL
ENABLE
R1
ENx
R2
1. Precision Enabled Threshold
Above 0.8V to enable the regulator, below 0.72V
(hysteresis) to shutdown the regulator.
VREG
TOP
RESISTOR
LEVEL DETECTOR
AND DECODER
SS12
OR
SS34
BOTTOM
RESISTOR
Programmable Soft Start: Soft start circuitry ramps the output
voltage in a controlled manner, limiting the inrush current. The
soft start time is set to 2 ms when the soft start pins are tied to VREG,
or it can be increased up to 8 ms by connecting a resistor divider
from the soft start pin to VREG and ground (Figure 6-2). This
configuration may be required to accommodate a specific start-up
sequence or an application with a large output capacitor. The
configurability and flexibility of the soft start enable large, complex
FPGAs and processors to power up in a safe, controlled manner.
2. Programmable Soft Start
The different soft start on each channel
can be programmable to be 2ms, 4ms, 8ms.
VDDIO
PWRGDMASK
PWRGD1
PWRGD2
PWRGD3
PWRGD4
PWRGD
MUX
Power-Good Output: An open-drain power-good output
(PWRGD) goes high when the selected buck regulators are
operating normally (Figure 6-3). The power-good pins allow
the power supply to signal the host system about its health. By
default, PWRGD monitors the output voltage on Buck 1, but
other channels can be custom ordered to control the PWRGD
pin. The status of each channel (PWRGx bit) can be read back via
the I2C interface on the ADP5050. A logic high on the PWRGx
bit indicates that the regulated output voltage is above 90.5% of
its nominal output. The PWRGx bit is set to logic low when the
regulated output voltage falls below 87.2% of its nominal output
for more than 50 µs. The PWRGD output is the logical AND
of the internal unmasked PWRGx signals. An internal PWRGx
signal must be high for at least 1 ms before PWRGD goes high;
if any PWRGx signal fails, PWRGD goes low with no delay. The
channels that control PWRGD (Channel 1 to Channel 4) are
specified by factory fuse or by setting bits via the I2C interface.
Analog Dialogue 47-11, November (2013)
0.8V
DEGLITCH
TIMER
1M
Precision Enable Inputs: Each regulator, including the LDO,
has an enable input with a precise 0.8-V reference (Figure 6-1).
When the voltage at an enable input is greater than 0.8 V, the
regulator is enabled; when the voltage falls below 0.725 V, the
regulator is disabled. An internal 1-MΩ pull-down resistor
prevents errors if the pin is left floating. The precision enable
threshold voltage allows easy sequencing within the device, as
well as with external supplies. As an example, if Buck 1 is set to
5 V, a resistor divider can be used to set an accurate 4.0-V trip
point to enable Buck 2, and so on, setting an accurate power-up
sequence for all outputs.
Active Output Discharge Switch: Each buck regulator
integrates a discharge switch from the switching node to ground
(Figure 6-4). Turned on when its associated regulator is disabled,
the switch helps the output capacitor to discharge quickly. The
typical resistance of the discharge switch is 250 Ω for Channel
1 to Channel 4. The active discharge switch pulls the output to
ground when the regulator is disabled, even when a large capacitive
load is present. This significantly increases the robustness of the
system, particularly when it is power cycled.
INPUT/OUTPUT
VOLTAGE
1ms VALIDATION
DELAY TIMER
3. PWRGD Output
The desirable PWRGDx from CH1 to CH4 can be
configured by the factory fuse or I2C.
BSTx
SW
DISCHARGE
SWITCH
L
VOUT
COUT
DISCHARGE
4. Active Output Discharge Switch
The output discharge switch can be turned ON to
shorten the discharge period of the output capacitors.
Figure 6. ADP5050 and ADP5052 simplify
power supply sequencing.
3
Figure 7 shows a typical power-up/power-down sequence.
EN1 TIED TO INTERNAL 5VREG FOR
AUTOMATIC
12V PLUG-IN
EN1 TIED TO STARTUP
INTERNALWHEN
5VREG FOR
AUTOMATIC STARTUP WHEN 12V PLUG-IN
12V INPUT
12V INPUT
PACKWOOD
12V (TIED TO VREG)
ADP5050
12V (TIED TO VREGEN1
)
115K
10K
10K
CH1: BUCK
PWRGD1
Vx
Vx
EN2
Vx STARTUP FIRSTLY, THEN ENABLE CH2
Vx STARTUP FIRSTLY, THEN ENABLE CH2
VCCAUX
1.8V @ 1.2A
VCCAUX
1.8V @ 1.2A
CH1: BUCK
EN1
PWRGD1
DUAL
DUAL
FETs
FETs
115K
115K/10K RESISTOR DIVIDER TO SET
THE
UVLORESISTOR
OF CH3/CH4
TO BETO
~9VSET
115K/10K
DIVIDER
THE UVLO OF CH3/CH4 TO BE ~9V
CH2: BUCK
EN2
1.2V @ 1.2A
CH2: BUCK
CH3/CH4 WOULD BE HELD OFF BY
PWRGD1
1.8V
REACHES
ITS
CH3/CH4 BEFORE
WOULD BE
HELD
OFF BY
90%
REGULATION
PWRGD1
BEFORE 1.8V REACHES ITS
90% REGULATION
1.2V @ 1.2A
EN3
INTERNAL ACTIVE DISCHARGE SWITCH CAN
BE
TURNEDACTIVE
ON TODISCHARGE
FULLY DISCHARGE
INTERNAL
SWITCH CAN
VCCO-3.3V
IN SHUTDOWN
BE TURNEDTO
ONZERO
TO FULLY
DISCHARGE
VCCO-2
2.5V @ 1.2A VCCO-3.3V TO ZERO IN SHUTDOWN
VCCO-2
CH3: BUCK
EN4
CH4: BUCK
EN4
CH4: BUCK
VDDIO
SDA
VDDIO
SCL
SDA
SCL
I2C INTERFACE CAN BE USED TO
TURN
OFF EACH
CHANNEL
I2C INTERFACE
CAN
BE USED TO
TURN OFF EACH CHANNEL
VCCO-1
3.3V @ 1.2A
VCCO-1
3.3V @ 1.2A
CH3: BUCK
EN3
2.5V @ 1.2A
OTHER
PURPOSE
OTHER
PURPOSE
CH5: LDO
CH5: LDO
VCCO = 3.3V
VCCO = 3.3V
VCCO = 3.3V
VCCO = 3.3V
ACTIVE DISCHARGE
3.3VCCO
TO ZERO
ACTIVE
DISCHARGE
3.3VCCO TO ZERO
VCCAUX = 1.8V
PWRGD =1.8V TO
START
UP
3.3VCCO
PWRGD
=1.8V
TO
START UP 3.3VCCO
12VIN
12VIN
PWRGD =1.8V
PWRGD =1.8V
a) 1.8V-VCCAUX STARTUP FIRSTLY, THEN 3.3V STARTUP UP BY
PWRGD AFTER 1.8V REACHES ITS 90% REGULATION PLUS 2ms
a) 1.8V-VCCAUX STARTUP FIRSTLY, THEN 3.3V STARTUP UP BY
PWRGD DELAY
PWRGD AFTER 1.8V REACHES ITS 90% REGULATION PLUS 2ms
PWRGD DELAY
I2C Interface
VCCAUX = 1.8V
VCCAUX = 1.8V
VCCAUX = 1.8V
VIN = ~9V TO SHUT
DOWN
3.3VCCO
VIN
= ~9V
TO SHUT
DOWN 3.3VCCO
b) 3.3V POWER-DOWN FIRSTLY AND FULLY DISCHARGED WHEN
12VIN DROPS BELOW ~9V, ALL OTHER VOLTAGES DISABLED WHEN
POWER-DOWN FIRSTLY AND FULLY DISCHARGED WHEN
b) 3.3V
12VIN DROPS BELOW <4V
DROPS BELOW ~9V, ALL OTHER VOLTAGES DISABLED WHEN
12VIN
12VIN DROPS BELOW <4V
Figure 7. Typical power-up/power-down sequence.
Figure 8 shows the values that can be programmed to monitor
the input voltage of the ADP5050.
The I2C interface enables advanced monitoring capability and basic
dynamic voltage scaling of the two buck regulator outputs (Channel 1
and Channel 4).
Junction Temperature Monitor: The junction temperature
can be monitored for faults such as overtemperature conditions.
If the junction temperature increases above a preset level (105°C,
115°C, or 125°C), an alert is signaled on nINT. Unlike thermal
shutdown, this function sends a warning signal, but does not shut
down the device. The ability to monitor the junction temperature
and alert the system processor to possible systems failures before
they happen increases the system reliability, as shown in Figure 9.
Input Voltage Monitor: The input voltage can be monitored
for faults such as undervoltage conditions. As an example, with
12 V applied to the input, the I2C interface is configured to trigger
an alert if the input voltage falls below 10.2 V. The signal on a
dedicated pin (nINT) tells the system processor that a problem
has occurred and shuts the system down for corrective action. The
ability to monitor the input voltage increases system reliability.
[3:0]
12V INPUT VOLTAGE
LVIN_TH[3:0] R/W
10.2V
(ADJUSTABLE)
INTERRUPT
TIME
Low input voltage detection on PVIN1.
These bits set the low input voltage detection threshold.
0000 = 4.2V (default)
0001 = 4.7V
0010 = 5.2V
0011 = 5.7V
0100 = 6.2V
0101 = 6.7V
0110 = 7.2V
0111 = 7.7V
1000 = 8.2V
1001 = 8.7V
1010 = 9.2V
1011 = 9.7V
1100 = 10.2V
1101 = 10.7V
1110 = 11.2V
1111 = low input voltage warning function disabled
Undervoltage monitor values.
Figure 8. Input undervoltage detection.
115˚
(ADJUSTABLE)
[5:4]
JUNCTION TEMPERATURE
TEMP_TH[1:0]
R/W
These bits set the junction temperature overheat threshold.
00 = temperature warning function disabled (default)
01 = 105°C
10 = 115°C
11 = 125°C
INTERRUPT
TIME
Low input voltage detection on PVIN1.
Figure 9. Junction temperature monitoring.
4
Analog Dialogue 47-11, November (2013)
Dynamic Voltage Scaling: Dynamic voltage scaling allows the
system to reduce power consumption by dynamically lowering the
power supply voltage on Channel 1 and Channel 4 for low-power
modes, or it can dynamically change the output voltage depending
on the system configuration and system loading. Also, the output
voltages of all four buck regulators can be set via the I2C interface,
as seen in Figure 10.
The phase shift of Channel 2, Channel 3, and Channel 4 can be
set to 0°, 90°, 180°, or 270° with respect to Channel 1 using the
I2C interface, as shown in Figure 12. When parallel operation is
configured to provide a single combined output of up to 8 A on
Channel 1 and Channel 2, the switching frequency of Channel 2
is locked to a 180˚ phase shift with respect to Channel 1.
SW1
Option 1: Resistor programmable output voltage
from 0.8V to V IN 0.85
Option 2: Fixed output voltage with I2C
programmability with these ranges for each channel
1
[CH1: 0.85V TO 1.60V, 25mV STEP]
SW2
[CH2: 3.3V TO 5.0V, ~300mV STEP]
2
[CH3: 1.2V TO 1.80V, 100mV STEP]
[CH4: 2.5V TO 5.5V, 100mV STEP]
SW3
Figure 10. ADP5050 output voltage options.
Low Noise Features
Several features reduce system noise generated by the power
supply:
Wide Resistor Programmable Switching Frequency Range:
A resistor on the RT pin programs the switching frequency
between 250 kHz and 1.4 MHz. This flexibility allows the power
supply designer to set the switching frequency to avoid system
noise bands.
Buck Regulator Phase Shifting: The phase shift of the buck
regulators can be programmed via the I2C interface. By default,
the phase shift between Channel 1 and Channel 2 and between
Channel 3 and Channel 4 is 180°, as shown in Figure 11. The
benefit of out-of-phase operation is reduced input ripple current
and less ground noise on the power supply.
0° REFERENCE
SW
180° PHASE SHIFT
CH1
(½ fSW
OPTIONAL)
CH2
90° PHASE SHIFT
0°, 90°,180°, OR 270°
ADJUSTABLE
270° PHASE SHIFT
CH3
(½ fSW
OPTIONAL)
CH4
Figure 11. Phase shift of the buck regulators
in the ADP5050/ADP5052.
Analog Dialogue 47-11, November (2013)
3
SW4
4
CH1 10.0V BW
CH3 10.0V BW
CH2 10.0V BW
CH4 10.0V BW
M400ns
A CH1
7.40V
Figure 12. Phase shift of buck regulators can
be configured via the I2C interface.
Clock Synchronization: The switching frequency can be
synchronized to an external clock in the 250-kHz to 1.4-MHz
range via the SYNC/MODE pin. This ability is important in
RF and noise-sensitive applications. When an external clock is
detected, the switching frequency transitions smoothly to its
frequency. When the external clock stops, the device switches
back to the internal clock and continues to operate normally.
Synchronizing to an external clock allows the system designer
to stay away from critical noise frequency bands and reduces the
noise generated by multiple devices in a system.
For successful synchronization, the internal switching frequency
must be programmed to a value close to that of the external clock
value; a frequency difference of less than ±15% is suggested.
The SYNC/MODE pin can be configured as a synchronization
clock output via a factory fuse or the I2C interface. A positive clock
pulse with a 50% duty cycle is generated at the SYNC/MODE
pin with a frequency equal to the internal switching frequency.
A short time delay (~15% of tSW ) occurs between the generated
synchronization clock and the Channel 1 switching node.
5
Fig ure 13 shows t wo dev ices con f ig ured in f requenc y
synchronization mode: one device is configured as the clock
output to synchronize the other device. A 100 kΩ pull-up resistor
should be used to prevent logic errors if the SYNC/MODE pin
is left floating.
ADIsimPower allows the user to quickly and easily input the
design requirements on the software interface shown in Figure 15.
STEP 1:
STEP 2:
OPTIMIZE FOR SIZE, COST,
OR EFFICIENCY
SPECIFY EACH CHANNEL’S
OPERATING CONDITIONS,
INCLUDING “DO NOT USE”
ADP5050/ADP5052
(LDO VERSION)
12V
5V @ 3A
CH1
BUCK
(4A)
2.2V @ 1.7A
CH2
BUCK
(4A)
ADP1754-1.8
ADP1754-1.8
1.8V @ 1A
CH3
BUCK
(1.2A)
ADP171-ADJ
3.3V @ 1.2A
1.8V @ 0.5A
1.8V @ 1.2A
1.29V @ 0.3A
1.5V @ 1A
CH4
BUCK
(1.2A)
1.8V
ADP3339-3.3
CH5
200MA LDO
ADP5051/ADP5053
(WDI VERSION)
0.945V @
0.2A
CH1
BUCK
(4A)
CLOCK
SYNC
0.92V @ 8A
CH2
BUCK
(4A)
1.2V @ 1.2A
CH3
BUCK
(1.2A)
12V
WDI
3.3V @ 1.2A
CH4
BUCK
(1.2A)
ADP171-ADJ
2.5V @ 0.3A
Figure 15. ADIsimPower software interface.
WATCHDOG
AND RESET
VTH
nRESET
A full bill of materials is generated with intelligent component
selection. Evaluation boards can be requested from within the
tool. The design tool allows for sophisticated controls for each
channel, as shown in Figure 16.
CLOCK
SYNC
Figure 13. RF application shows two devices
synchronized to reduce power supply noise.
Both devices are synchronized to the same clock, so the phase
shift between Channel 1 of the first device and Channel 1 of the
second device is 0°, as shown in Figure 14.
SYNC-OUT
AT FIRST
ADP5050
1
SW1
AT FIRST
ADP5050
(a)
2
SW1
AT SECOND
ADP5050
3
CH1 2.00V BW
CH3 5.00V BW
CH2 5.00V BW
M400ns
A CH1
5V RAIL
560mV
4.5V
Figure 14. Waveforms of two ADP5050 devices
operating in synchronized mode.
VOLTAGE
ADIsimPower Design Tool
RAIL 1
™
A DIsi m Power now suppor ts t he A DP5050/A DP5052
multichannel high-voltage PMUs, which power 4/5 channels
with load current up to 4 A per channel from inputs up to 15 V.
The design tool allows users to optimize the design by cascading
channels, placing high-current channels in parallel to create an 8-A
rail, and considering the thermal contributions of each channel.
With the advanced features, users can independently specify
each channel’s performance for ripple and transient performance,
switching frequency, and channels that support half the master
frequency.
6
TIME
(b)
RAIL CAN BE FURTHER DELAYED
USING AN RC DELAY
Figure 16. (a) Ripple, transient, and response can be specified for each rail. (b) Advanced sequencing requirements using precision enable.
Analog Dialogue 47-11, November (2013)
ADIsimPower gives the power designer quick access to accurate, tested, reliable performance data, as shown in Figure 17.
Figure 17. ADIsimPower simulation output.
The design can then be assembled on an evaluation board, as shown in Figure 18.
ADP505x IC
28.3mm × 21.2mm
Figure 18. Power supply circuit using ADP5050/ADP5052.
Analog Dialogue 47-11, November (2013)
7
ADP5050/ADP5052/ADP5051/ADP5053 Specifications
Part
Number
Description
VIN (V)
VOUT (V)
Number
of
Outputs
Output
Current
(mA)
I2C
Key Features
Package
Price
($U.S.)
ADP5050
Quad Buck
Regulator,
LDO, I2C
Buck: 4.5 to 15
0.8 to 0.85 × VIN
2 × Buck
4000, 2500,
or 1200
Yes
48-lead
LFCSP
4.39
2 × Buck
1200
I2C interface with
individual enable
pins and power good
LDO: 1.7 to 5.5
0.5 to 4.75
LDO
200
Quad Buck
Regulator,
POR/WDI, I2C
Buck: 4.5 to 15
0.8 to 0.85 × VIN
2 × Buck
4000, 2500,
or 1200
Yes
48-lead
LFCSP
4.59
2 × Buck
1200
I2C interface with
individual enable
pins and power good
Quad Buck
Regulator,
LDO
Buck: 4.5 to 15
2 × Buck
4000, 2500,
or 1200
No
Individual enable
pins and power good
48-lead
LFCSP
3.59
2 × Buck
1200
No
Individual enable
pins and power good
48-lead
LFCSP
3.79
ADP5051
ADP5052
ADP5053
Quad Buck
Regulator,
POR/WDI
0.8 to 0.85 × VIN
LDO: 1.7 to 5.5
0.5 to 4.75
LDO
200
Buck: 4.5 to 15
0.8 to 0.85 × VIN
2 × Buck
4000, 2500,
or 1200
2 × Buck
1200
ADP5050/
ADP5052
12V/5V
INPUT
OPTIONAL
I 2C
ADP5051/
ADP5053
12V/5V
INPUT
4A BUCK REG1
1.0V
2.5V
4A BUCK REG1
2.5V
1.2A BUCK REG
1.8V
1.2A BUCK REG
1.8V
1.2A BUCK REG
3.3V
1.2A BUCK REG
3.3V
200mA LDO
1.5V
4A BUCK REG1
1.2V
4A BUCK REG1
OPTIONAL
I 2C
MR
WDI
PWRGD
1RESISTOR
VTHR
POWER-ON
RESET AND
WATCHDOG
RESET
PWRGD
PROGRAMMABLE CURRENT LIMIT (4 A, 2.5 A, or 1.2 A).
Figure 19. ADP5050/ADP5051/ADP5052/ADP5053: quad buck switching regulators with LDO or POR/WDI in LFCSP.
Conclusion
New highly integrated PMUs are enabling complex power
management solutions with high power efficiency, high reliability,
and ultrasmall size; and new design tools combined with flexible
integrated circuits reduce the time to market for these complex
power supplies. The ADP505x family, the latest addition to ADI’s
portfolio of highly integrated multi-output regulators, allows a
single IC to be used quickly and easily in many different applications,
reducing power supply design time. To discuss technical aspects of
these devices, please visit the EngineerZone® forum.
8
Author
Maurice O’Brien [[email protected]]
joined Analog Devices in 2002, following
his graduation from t he Universit y of
Limerick, Ireland, with a bachelor’s degree
in electronic engineering. He currently works
as a product marketing manager in the Power
Management product line. In his spare time,
Maurice enjoys horse riding, outdoor sports,
and travel.
Analog Dialogue 47-11, November (2013)