SiC471, SiC472, SiC473, SiC474
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4.5 V to 55 V Input, 3 A, 5 A, 8 A, 12 A
microBUCK® DC/DC Converter
DESCRIPTION
The SiC47x is a family of wide input voltage, high efficiency
synchronous buck regulators with integrated high side
and low side power MOSFETs. Its power stage is capable
of supplying high continuous current at up to 2 MHz
switching frequency. This regulator produces an adjustable
output voltage down to 0.8 V from 4.5 V to 55 V input
rail to accommodate a variety of applications, including
computing, consumer electronics, telecom, and industrial.
SiC47x’s architecture allows for ultrafast transient response
with minimum output capacitance and tight ripple regulation
at very light load. The device enables loop stability
regardless of the type of output capacitor used, including
low ESR ceramic capacitors. The device also incorporates a
power saving scheme that significantly increases light load
efficiency. The regulator integrates a full protection feature
set, including over current protection (OCP), output
overvoltage protection (OVP), short circuit protection (SCP),
output undervoltage protection (UVP) and over temperature
protection (OTP). It also has UVLO for input rail and a user
programmable soft start.
The SiC47x family is available in 3 A, 5 A, 8 A, 12 A pin
compatible 5 mm by 5 mm lead (Pb)-free power enhanced
MLP55-27L package.
TYPICAL APPLICATION CIRCUIT
Fig. 1 - Typical Application Circuit for SiC47x
FEATURES
• Versatile
- Single supply operation from 4.5 V to 55 V
input voltage
- Adjustable output voltage down to 0.8 V
- Scalable solution 3 A (SiC474), 5 A (SiC473),
8 A (SiC472), 12 A (SiC471)
- Output voltage tracking and sequencing with
pre-bias start up
- ± 1 % output voltage accuracy at -40 °C to +125 °C
• Highly efficient
- 98 % peak efficiency
- 4 A supply current at shutdown
- 235 A operating current, not switching
• Highly configurable
- Adjustable switching frequency from 100 kHz to 2 MHz
- Adjustable soft start and adjustable current limit
- 3 modes of operation, forced continuous conduction,
power save or ultrasonic
• Robust and reliable
- Output over voltage protection
- Output under voltage / short circuit protection with auto
retry
- Power good flag and over temperature protection
- Supported by Vishay PowerCAD online design
simulation
• Design support tools
-
PowerCAD online design simulation (vishay.transim.com)
-
External component calculator (www.vishay.com/doc?75760)
- Schematic, design, BOM, and gerber files
(www.vishay.com/doc?75763)
• Material categorization: for definitions of compliance
please see www.vishay.com/doc?99912
APPLICATIONS
• Industrial and automation
• Home automation
• Industrial and server computing
• Networking, telecom, and base station power supplies
• Unregulated wall transformer
• Robotics
• High end hobby electronics: remote control cars, planes,
and drones
• Battery management systems
• Power tools
• Vending, ATM, and slot machines
Fig. 2 - SiC472 Efficiency vs. Output Current
V
IN
P
GOOD
EN
V
DD
SW
P
GND
A
GND
C
OUT
V
OUT
V
FB
BOOT
C
BOOT
SS
V
SNS
Rx Cx
R
limit
R
fsw
f
SW
I
LIMIT
C
IN
PHASE
COMP R
comp
V
CIN
V
DRV
MODE
C
ss
C
comp
Cy
ULTRASONIC
INPUT
4.5 V
DC
to 55 V
DC
R
up
R
down
SiC47x
10
100
1000
10000
80
82
84
86
88
90
92
94
96
98
100
012345678
Axis Title
1st line
2nd line
2nd line
eff - Efficiency (%)
IOUT - Output Current (A)
VIN = 24 V, VOUT = 12 V
VIN = 48 V, VOUT = 5 V
VIN = 24 V, VOUT = 5 V
VIN = 48 V, VOUT = 12 V
SiC471, SiC472, SiC473, SiC474
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PIN CONFIGURATION
Fig. 3 - SiC47x Pin Configuration
PIN DESCRIPTION
PIN NUMBER SYMBOL DESCRIPTION
1V
CIN Supply voltage for internal regulators VDD and VDRV. This pin should be tied to VIN, but can also be
connected to a lower supply voltage (> 5 V) to reduce losses in the internal linear regulators
2P
GOOD Open-drain power good indicator - high impedance indicates power is good. An external pull-up
resistor is required
3EN
Enable pin. Tie high/low to enable/disable the IC accordingly. This is a high voltage compatible pin,
can be tied to VIN
4 BOOT High side driver bootstrap voltage
5, 6 PHASE Return path of high side gate driver
7, 8, 29 VIN Power stage input voltage. Drain of high side MOSFET
9, 10, 11, 17, 30 PGND Power ground
12, 13, 14 SW Power stage switch node
15 GL Low side MOSFET gate signal
16 VDRV Supply voltage for internal gate driver. When using the internal LDO as a bias power supply, VDRV is
the LDO output. Connect a 4.7 µF decoupling capacitor to PGND
18 ULTRASONIC
Float to disable ultrasonic mode, connect to VDD to enable. Depending on the operation mode set by
the mode pin, power save mode or forced continuous mode will be enabled when the ultrasonic
mode is disabled
19 SS Set the soft start ramp by connecting a capacitor to AGND. An internal current source will charge the
capacitor
20 VSNS Power inductor signal feedback pin for system stability compensation
21 COMP Output of the internal error amplifier. The feedback loop compensation network is connected from
this pin to the AGND pin
22 VFB Feedback input for switching regulator used to program the output voltage - connect to an external
resistor divider from VOUT to AGND
23, 28 AGND Analog ground
24 fSW Set the on-time by connecting a resistor to AGND
25 ILIMIT Set the current limit by connecting a resistor to AGND
26 VDD Bias supply for the IC. VDD is an LDO output, connect a 1 µF decoupling capacitor to AGND
27 MODE Set various operation modes by connecting a resistor to AGND. See specification table for details
ķ
SS 19
ULTRASONIC 18
PGND 17
VDRV 16
GL 15
SW 14
SW 13
SW 12
PGND 11
PGND 10
PGND 9
VIN 8
VIN 7
1 VCIN
2 PGOOD
3 EN
4 BOOT
5 PHASE
6 PHASE
19 SS
18 ULTRASONIC
17 PGND
16 VDRV
15 GL
14 SW
13 SW
12 SW
VCIN 1
PGOOD 2
EN 3
BOOT 4
PHASE 5
PHASE 6
27 MODE
26 VDD
25 ILIM
24 fSW
23 AGND
22 VFB
21 COMP
20 VSNS
28 AGND
30
VIN 29 PGND
PGND 11
PGND 10
PGND 9
VIN 8
VIN 7
IJ
ķ
27 MODE
26 VDD
25 ILIM
24 fSW
23 AGND
22 VFB
21 COMP
20 VSNS
28 AGND
29
VIN
30 PGND
SiC471, SiC472, SiC473, SiC474
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PART MARKING INFORMATION
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation
of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum
rating/conditions for extended periods may affect device reliability.
ORDERING INFORMATION
PART NUMBER PACKAGE MARKING CODE
SiC471ED-T1-GE3 PowerPAK® MLP55-27L SiC471
SiC471EVB Reference board
SiC472ED-T1-GE3 PowerPAK® MLP55-27L SiC472
SiC472EVB Reference board
SiC473ED-T1-GE3 PowerPAK® MLP55-27L SiC473
SiC473EVB Reference board
SiC474ED-T1-GE3 PowerPAK® MLP55-27L SiC474
SiC474EVB Reference board
ABSOLUTE MAXIMUM RATINGS (TA = 25 °C, unless otherwise noted)
ELECTRICAL PARAMETER CONDITIONS LIMITS UNIT
EN, VCIN, VIN Reference to PGND -0.3 to +60
V
SW / PHASE Reference to PGND -0.3 to +60
VDRV Reference to PGND -0.3 to +6
VDD Reference to AGND -0.3 to +6
SW / PHASE (AC) Reference to PGND; 100 ns -10 to +66
BOOT -0.3 to VPHASE + VDRV
AGND to PGND -0.3 to +0.3
All other pins Reference to AGND -0.3 to VDD + 0.3
Temperature
Junction temperature TJ-40 to +150 °C
Storage temperature TSTG -65 to +150
Power Dissipation
Thermal resistance from junction-to-ambient 12 °C/W
Thermal resistance from junction-to-case 2
ESD Protection
Electrostatic discharge protection Human body model, JESD22-A114 2000 V
Charged device model, JESD22-A101 500
= pin 1 indicator
P/N = part number code
=Siliconix logo
=ESD symbol
F=assembly factory code
Y = year code
WW = week code
LL = lot code
F Y W W
P/N
LL
SiC471, SiC472, SiC473, SiC474
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Note
(1) For input voltages below 5 V, provide a separate supply to VCIN of at least 5 V to prevent the internal VDD rail UVLO from triggering
RECOMMENDED OPERATING CONDITIONS (all voltages referenced to GND = 0 V)
PARAMETER MIN. TYP. MAX. UNIT
Input voltage (VIN)4.5-55
V
Control input voltage (VCIN) (1) 4.5 - 55
Enable (EN) 0 - 55
Bias supply (VDD) 4.75 5 5.25
Drive supply voltage (VDRV) 4.75 5.3 5.55
Output voltage (VOUT) 0.8 - 0.92 x VIN
Temperature
Recommended ambient temperature -40 to +105 °C
Operating junction temperature -40 to +125
ELECTRICAL SPECIFICATIONS (VIN = VCIN = 48 V, VEN = 5 V, TJ = -40 °C to +125 °C, unless otherwise stated)
PARAMETER SYMBOL TEST CONDITIONS MIN. TYP. MAX. UNIT
Power Supplies
VDD supply VDD
VIN = VCIN = 6 V to 55 V 4.75 5 5.25 V
VIN = VCIN = 5 V 4.7 5 -
VDD dropout VDD_DROPOUT VIN = VCIN = 5 V, IVDD = 1 mA - 70 - mV
VDD UVLO threshold, rising VDD_UVLO 4 4.25 4.5 V
VDD UVLO hysteresis VDD_UVLO_HYST - 225 - mV
Maximum VDD current IDD VIN = VCIN = 6 V to 55 V 3 - - mA
VDRV supply VDRV
VIN = VCIN = 6 V to 55 V 5.1 5.3 5.55 V
VIN = VCIN = 5 V 4.8 5 5.2
VDRV dropout VDRV_DROPOUT VIN = VCIN = 5 V, IVDD = 10 mA - 160 - mV
Maximum VDRV current VDRV VIN = VCIN = 6 V to 55 V 50 - - mA
VDRV UVLO threshold, rising VDRV_UVLO 4 4.25 4.5 V
VDRV UVLO hysteresis VDRV_UVLO_HYST - 295 - mV
Input current IVCIN Non-switching, VFB > 0.8 V - 235 325 µA
Shutdown current IVCIN_SHDN VEN = 0 V - 4 8
Controller and Timing
Feedback voltage VFB
TJ = 25 °C 796 800 804 m/V
TJ = -40 °C to +125 °C (1) 792 800 808
VFB input bias current IFB -2-pA
Transconductance gm-0.3-mS
COMP source current ICOMP_SOURCE 15 20 - µA
COMP sink current ICOMP_SINK 15 20 -
Minimum on-time tON_MIN. - 90 110 ns
tON accuracy tON_ACCURACY -10 - 10 %
On-time range tON_RANGE 110 - 8000 ns
Frequency range fsw
Ultrasonic mode enabled 20 - 2000 kHz
Ultrasonic mode disabled 0 - 2000
Minimum off-time tOFF_MIN. 190 250 310 ns
Soft start current ISS 357µA
Soft start voltage VSS When VOUT reaches regulation - 1.5 - V
SiC471, SiC472, SiC473, SiC474
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Notes
(1) Guaranteed by design
(2) Guaranteed by design for SiC473 OCP measurements
Fault Protections
Valley current limit IOCP
SiC471 (12 A),
RILIM = 60 k, TJ = -10 °C to +125 °C 12 15 18
A
SiC472 (8 A),
RILIM = 60 k, TJ = -10 °C to +125 °C 81012
SiC473 (5 A),
RILIM = 43 k, TJ = -10 °C to +125 °C (2) 5.6 7 8.4
SiC474 (3 A),
RILIM = 60 k, TJ = -10 °C to +125 °C 456
Output OVP threshold VOVP VFB with respect to 0.8 V reference -20-%
Output UVP threshold VUVP --80-
Over temperature protection TOTP_RISING Rising temperature - 150 - °C
TOTP_HYST Hysteresis - 35 -
Power Good
Power good output threshold VFB_RISING_VTH_OV VFB rising above 0.8 V reference - 20 - %
VFB_FALLING_VTH_UV VFB falling below 0.8 V reference - -10 -
Power good hysteresis VFB_HYST -50-mV
Power good on resistance RON_PGOOD -7.515
Power good delay time tDLY_PGOOD 15 25 35 µs
EN / MODE / Ultrasonic Threshold
EN logic high level VEN_H -1.35-
VEN logic low level VEN_L -1.2-
EN hysteresis VHYST -0.15-
EN pull down resistance REN -5-M
Ultrasonic mode high Level VULTRASONIC_H 2--V
Ultrasonic mode low level VULTRASONIC_L --0.8
Mode pull up current IMODE 3.75 5 6.25 µA
Mode 1
RMODE
Power save mode enabled, VDD, VDRV
Pre-reg on 0 2 100
k
Mode 2 Power save mode disabled, VDD, VDRV
Pre-reg on 298 301 304
Mode 3 Power save mode disabled, VDRV Pre-reg
off, VDD Pre-reg on, provide external VDRV 494 499 504
Mode 4 Power save mode enabled, VDRV Pre-reg off,
VDD Pre-reg on, provide external VDRV 900 1000 1100
ELECTRICAL SPECIFICATIONS (VIN = VCIN = 48 V, VEN = 5 V, TJ = -40 °C to +125 °C, unless otherwise stated)
PARAMETER SYMBOL TEST CONDITIONS MIN. TYP. MAX. UNIT
SiC471, SiC472, SiC473, SiC474
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FUNCTIONAL BLOCK DIAGRAM
Fig. 4 - SiC47x Functional Block Diagram
OPERATIONAL DESCRIPTION
Device Overview
SiC47x is a high efficiency synchronous buck regulator
family capable of delivering up to 12 A continuous current.
The device has programmable switching frequency of
100 kHz to 2 MHz. The voltage mode, constant on time
control scheme delivers fast transient response, minimizes
the number of external components and enables loop
stability regardless of the type of output capacitor used,
including low ESR ceramic capacitors. The device also
incorporates a power saving feature that enables diode
emulation mode and frequency fold back as the load
decreases.
SiC47x has a full set of protection and monitoring features:
• Over current protection in pulse-by-pulse mode
• Output overvoltage protection
• Output undervoltage protection with auto retry
• Over temperature protection with hysteresis
• Dedicated enable pin for easy power sequencing
• Power good open drain output
• This device is available in MLP55-27L package to deliver
high power density and minimize PCB area
Power Stage
SiC47x integrates a high performance power stage with a
n-channel high side MOSFET and a n-channel low side
MOSFET optimized to achieve up to 98 % efficiency.
The power input voltage (VIN) can go up to 55 V and down
as low as 4.5 V for power conversion.
Control Scheme
SiC47x employs a voltage mode COT control mechanism in
conjunction with adaptive zero current detection which
allows for power saving in discontinuous conduction mode
(DCM). The switching frequency, fSW, is set by an external
resistor to AGND, Rfsw. The SiC47x operates between
100 kHz to 2 MHz depending on VIN and VOUT conditions.
Note, as long as VIN and VCIN are connected together, fSW
has no dependency on VIN as the on time is adjusted as VIN
varies. During steady-state operation, feedback voltage
(VFB) is compared with internal reference (0.8 V typ.) and the
amplified error signal (VCOMP) is generated at the comp node
by the external compensation components, RCOMP and
CCOMP. An externally generated ramp signal and VCOMP feed
into a comparator. Once VRAMP crosses VCOMP, an on-time
OTA
0.8 V
5 µA
PHASE
PHASE
A
GND
P
GND
Over
current
Over
temperature
Power good
Zero
crossing
I
LIMIT
V
FB
SS
Over voltage
under voltage
V
SNS
V
DRV
V
DD
EN
f
SW
ULTRASONIC
MODE
COMP
V
FB
V
DD
V
DD
5 µA
V
CIN
BOOT V
IN
PHASE
SW
P
GOOD
GL
LS
driver
HS
driver
Control
logic V
DRV
Ramp
PWM
COMP
Reference
MODE
Enable
On time
generator
V
DRV
regulator
V
DD
UVLO
V
DD
regulator
t
ON
Min. t
OFF
Sync
rectier
HS UVLO
Rfsw
VOUT
fsw 190 10-12
---------------------------------------------
=
SiC471, SiC472, SiC473, SiC474
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pulse is generated for a fixed time. During the on-time pulse,
the high side MOSFET will be turned on. Once the on-time
pulse expires, the low side MOSFET will be turned on after
a dead time period. The low side MOSFET will stay on for a
minimum duration equal to the minimum off-time (tOFF_MIN.)
and remains on until VRAMP crosses VCOMP. The cycle is then
repeated.
Fig. 6 illustrates the basic block diagram for voltage mode,
constant on time architecture with external ripple injection,
VRAMP, while Fig. 5 illustrates the basic operational principle.
Fig. 5 - SiC47x Operational Principle
The need for ripple injection in this architecture is explained
below. First, let us understand the basic principles of this
control architecture:
• The reference of a basic voltage mode COT regulator
is replaced with a high gain error amplifier loop. The loop
ensures the DC component of the output voltage follows
the internal accurate reference voltage, providing
excellent regulation
• A second voltage feedback path via VSNS with a VRAMP
scheme ensures rapid correction of the transient
perturbation
• This establishes two voltage loops, one is the steady state
voltage feedback path (via the FB pin) and the other is the
feed forward path (via the VSNS pin). The scheme gives the
user the fast transient response of a COT regulator and
the stable, jitter free, line and load regulation performance
of a PWM controller
Choosing the Ripple Injection Component Values
For stability purposes the SiC47x requires adequate ripple
injection amplitude. Adequate ripple amplitude is required
for two main reasons:
1. To reduce jitter due to noise coupled into the system
2. To provide stable operation. Sub harmonic oscillation
can occur with constant on time ripple control if below
condition is not met
Therefore, when the converter design uses an all ceramic
output capacitor or other low ESR output capacitors,
instability can occur. In order to avoid this, a VRAMP network
is used to increase the equivalent RESR in order to satisfy the
above condition. The VRAMP amplitude must be large
enough to avoid instability or noise sensitivity but not too
large that it degrades transient performance. To ensure
stable operation under CCM, DCM and ultrasonic mode,
minimum VRAMP amplitude of 100 mV is recommended for
the SiC47x family of regulators. A maximum VRAMP of
900 mV is recommended so as not to degrade transient
response.
Fig. 6 - SiC47x Control Block Diagram
Below is the equation for calculating the VRAMP amplitude.
VRAMP amplitude is a function of VIN, VOUT, and switching
frequency and should be adjusted whenever VIN, VOUT, or
switching frequency is changed.
For a given buck regulator design, VOUT and switching
frequency is typically fixed, while the converter may be
expected to work for a wide VIN range. The VRAMP amplitude
will increase as VIN is increased and increase the power
dissipated by Rx. A proper selection of RX, package size and
value, should take into account the maximum power
dissipation at the expected operating conditions.
In order to optimize the VRAMP amplitude over a desired VIN
range use the following procedure to calculate Rx, Cx, and
Cy.
1. The equation below calculates RX as a function of VIN,
VOUT, and maximum allowable power dissipated by RX.
where PRX_MAX. is the maximum allowed power
dissipation in Rx. Note, the maximum power dissipation
of a 0603 sized resistor is typically 25 mW. Power
dissipation derating must be taken into account for high
ambient temperatures
2. The equation below calculates CX_MIN. as a function of
VIN and maximum allowed VRAMP amplitude.
where VRAMP_MAX. = 900 mV
3. Using VRAMP equation, calculate VRAMP_MIN. at minimum
VIN based on the Rx and the minimum Cx value
calculated above
4. If VRAMP_MIN. is > 200 mV, set Cx to CX_MIN., otherwise set
Cx to (Cx_MIN. x VRAMP_MIN./200 mV). If VRIPPLE_MIN. is
< 100 mV, increase PRX_MAX. and recalculate RX and CX
5. Cy should be large enough not to distort the VRAMP and
small enough not to load excessively the VRAMP network
(Rx and Cx). Please use the follow formula:
Cy = 1/(0.82 x fsw)
This procedure allows for a maximum range of operation. In
order to simplify the procedure for calculating VRAMP and
compensation components, a calculator is provided
(visit www.vishay.com/doc?65124).
Fixed on-time
VRAMP
VCOMP
PWM
ESR COUT
tON
2
---------
Cx
Rx
L
Cy
EA
Ripple
based
controller
R_FB_H
R_FB_L
REF
RCOMP
CCOMP
Load
Q1
Q2
VIN
COUT
CIN
VRAMP
VIN VOUT
–VOUT
VIN fsw
Cx
Rx

------------------------------------------------------
=
Rx
VIN_MAX. VOUT 1D–
PRX_MAX.
--------------------------------------------------------------------
=
CX_MIN.
PRX _MAX.
VIN_MAX. fsw VRAMP_MAX.
---------------------------------------------------------------------------
=
SiC471, SiC472, SiC473, SiC474
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Error Amplifier Compensation Value Selection (for reference only)
RCOMP and CCOMP in the Fig. 6 are the components used to compensate the control loop.
For optimal transient response, the crossover frequency should be:
• Set typically at 1/10th to 1/5th of the converter switching frequency (Vishay’s component calculator tool uses 1/10th the
converter switching frequency)
• Be above the LC filter resonance frequency which is 1/2
The procedure to select the RCOMP and CCOMP such that the above conditions are met is as follows:
1. Plot the magnitude and phase of the control to output transfer function using the equation below.
Control to output transfer function.
Where A = (2VIN x Rx x Cx x f)/VOUT, Rx, Cx, Cy are components for ripple injection as shown in Fig. 6 and Ry is the internal
impedance of the VSNS pin and is = 65 k.
Co - output capacitance
Rc - output capacitor ESR
2. From the plot of the control to output transfer function, determine the gain and phase at the crossover frequency
3. Calculate the RCOMP using the equation
where GH is the gain of the transfer function at cross over frequency, “gm” is the transconductance of the error amplifier
(300 µS) and rFB is the ratio of the feedback divider, rFB = R_FB_L/(R_FB_L + R_FB_H)
4. Select CCOMP based on the placement of the zero such that phase margin is sufficient at the cross over frequency. A phase
margin of over 60° is sufficient for converter stability. A good starting point is to place the compensation zero at 1/5th of the
LC pole
Once the component values are calculated, it is now possible to calculate the total loop gain. The total loop gain is the product
of the control to output transfer function and the error amplifier transfer function.
The transfer function of the error amplifier is given by the equation below.
Where Ro = 40 M is the output resistance of the transconductance amplifier.
Total loop transfer function = H(s)G(s)
An automated calculator (visit www.vishay.com/doc?75760) is provided to assist the user to determine VRAMP components as
well as error amplifier compensation components using user selected operating conditions.
LC
H(s) A 1sR
CCo
+1sR
xCx
+1sR
yCy
+
1sL
Ro
-------s2LCo
++


1sR
xCx
+1sR
yCy
+ARyCys1sR
xCx
L
Ro
-------
+


s2RxRcCxCoLCo
++++
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
=
RCOMP
1
GHgmrFB
--------------------------------------
=
CCOMP
5LC
RCOMP
-------------------
=
SiC471, SiC472, SiC473, SiC474
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For technical questions, contact: powerictechsupport@vishay.com
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
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Power-Save Mode, Mode Pin, and Ultrasonic Pin Operation
To improve efficiency at light-loads, SiC47x provides a set
of innovative implementations to reduce low side
re-circulating current and switching losses. The internal zero
crossing detector monitors SW node voltage to determine
when inductor current starts to flow negatively. In power
saving mode, as soon as inductor current crosses zero, the
device first deploys diode mode by turning off the low side
MOSFET. If load further decreases, switching frequency is
reduced proportional to the load condition to save switching
losses while keeping output ripple within tolerance. If the
ultrasonic pin is tied to VDD, the minimum switching
frequency in discontinuous mode is > 20 kHz to avoid
switching frequencies in the audible range. If this feature is
not required ultrasonic mode can be disabled by floating the
ULTRASONIC pin. When ultrasonic mode is disabled, the
regulator will operate in forced continuous mode or power
save mode where there is no limit to the lower frequency
limit. In this state, at zero load, switching frequency can go
as low as hundreds of hertz.
To improve the converter efficiency, the user can choose to
disable the internal VDRV regulator by picking either mode 3
or mode 4 and connecting a 5 V supply to the VDRV pin. This
reduces power dissipation in the SiC47x by eliminating the
VDRV linear regulator losses.
The mode pin supports several modes of operation as
shown in table 1. An internal current source is used to set
the voltage on this pin using an external resistor:
Note
(1) Connect a 5 V (± 5 %) supply to the VDRV pin
The mode pin is not latched to any state and can be
changed on the fly.
OUTPUT MONITORING AND PROTECTION FEATURES
Output Over-Current Protection (OCP)
SiC47x has pulse-by-pulse over current limit control. The
inductor current is monitored during low side MOSFET
conduction time through RDS(on) sensing. After a pre-defined
blanking time, the inductor current is compared with an
internal OCP threshold. If inductor current is higher than
OCP threshold, high side MOSFET is kept off until the
inductor current falls below OCP threshold.
OCP is enabled immediately after VDD passes UVLO level.
OCP is set by an external resistor, RLIM to AGND. (See table 2)
Fig. 7 - Over-Current Protection Illustration
Output Undervoltage Protection (UVP)
UVP is implemented by monitoring the FB pin. If the voltage
level at FB drops below 0.16 V for more than 25 µs, a UVP
event is recognized and both high side and low side
MOSFETs are turned off. After a duration equivalent to
20 soft start periods, the IC attempts to re-start. If the fault
condition still exists, the above cycle will be repeated.
UVP is only active after the completion of soft-start
sequence.
Output Over Voltage Protection (OVP)
OVP is implemented by monitoring the FB pin. If the voltage
level at FB rising above 0.96 V, a OVP event is recognized
and both high side and low side MOSFETs are turned off.
Normal operation is resumed once FB voltage drop below
0.91 V.
Over Temperature Protection (OTP)
OTP is implemented by monitoring the junction
temperature. If the junction temperature rises above 150 °C,
a OTP event is recognized and both high side and low
MOSFETs are turned off. After the junction temperature falls
below 115 °C (35 °C hysteresis), the device restarts by
initiating a soft start sequence.
Sequencing of Input / Output Supplies
SiC47x has no sequencing requirements on its supplies or
enables (VIN, VCIN, VDD, VDRV, EN).
Enable
The SiC47x has an enable pin to turn the part on and off.
Driving this pin above 1.4 V enables the device, while driving
the pin below 0.4 V disables the device.
The EN pin is internally pulled to AGND by a 5 M resistor to
prevent unwanted turn on due to a floating GPIO.
Soft-Start
During soft start time period, inrush current is limited and the
output voltage is ramped gradually. The following control
scheme is implemented:
Once the VDD voltage reaches the UVLO trip point, an
internal “Soft start Reference” (SR) begins to ramp up. The
SR ramp rate is determined by the external soft start
capacitor and an internal 5 µA current source tied to the soft
start pin.
The internal SR signal is used as a reference voltage to the
error amplifier (see functional block diagram). The control
scheme guarantees that the output voltage during the soft
start interval will ramp up coincidently with the SR voltage.
The soft-start time, tSS, is adjustable by calculating a
capacitor value from the following equation.
During soft-start period, OCP is activated. Short circuit
protection is not active until soft-start is complete.
TABLE 1 - OPERATION MODES
MODE RANGE (k)POWER SAVE
MODE
INTERNAL VDRV
REGULATOR
1 0 to 100 Enabled ON
2 298 to 304 Disabled ON
3 494 to 504 Disabled OFF (1)
4 900 to 1100 Enabled OFF (1)
Iload
OCPthreshold
Iinductor
GH
tss
Css x 0.8 V
5 µA
------------------------------
=
SiC471, SiC472, SiC473, SiC474
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S18-0939-Rev. C, 17-Sep-2018 10 Document Number: 75786
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Pre-Bias Start-Up
In case of pre-bias startup, output is monitored through FB
pin. If the sensed voltage on FB is higher than the internal
reference ramp value, control logic prevents high side and
low side MOSFETs from switching to avoid negative output
voltage spike and excessive current sinking through low
side MOSFET.
Fig. 8 - Pre-Bias Start-Up
Power Good
SiC47x’s power good is an open-drain output. Pull PGOOD
pin high through a > 10K resistor to use this signal. Power
good window is shown in Fig. 9. If voltage on FB pin is out
of this window, PGOOD signal is de-asserted by pulling down
to AGND. To prevent false triggering during transient events,
PGOOD has a 25 µs blanking time.
Fig. 9 - PGOOD Window
EXAMPLE SCHEMATIC OF SiC472
Fig. 10 - SiC472 Configured for 6 V to 55 V Input, 5 V Output at 6 A, 500 kHz Operation with Ultrasonic Power Save Mode Enabled
all Ceramic Output Capacitance Design
Vref (0.8 V)
VFB
VFB_Rising_Vth_OV
(typ. = 0.96 V) VFB_Falling_Vth_OV
(typ. = 0.91 V)
VFB_Falling_Vth_UV
(typ. = 0.72 V) VFB_Rising_Vth_UV
(typ. = 0.77 V)
PG
Pull-high
Pull-low
Notes in small black text near
component values refer to Vishay
SiC47x spreadsheet calcualtor
references.
Analog ground (AGND), and
power ground (PGND) are
tied internally in the SiC47x
Rmode
Cdd
Rlim
R_ f sw
R_ F B_L
Rcomp Ccomp
Mode
VDD
ILIMIT
FSW
AGND
VFB
COMP
VCIN
VIN-PAD
VIN1
VIN2
AGND - PA D
PGND - PAD
PGND 1
PGND2
PGND3
PGND
EN
PHASE2
PHASE1
BOOT
ULTRASONIC
PGOO D
SS
GL
VDRV
SW1
SW2
SW3
VSNS
SiC472
+Vout
R_ F B_H
Cout_B
PGND
AGND
Cout_D
Cx
Rx
L
Cdrv
+VIN
Cin_D
Cin
R_ E N_ H
R
_boot
C_ b o o t
R_ E N_ L
Css
R_ P GD
R_ U_ SON IC
EN
P
GOO D
Cy
Cout_C
1
29
7
8
28
30
9
10
11
17
15
16
12
13
14
20
21
22
23
24
25
26
27
19
2
18
4
5
6
3
4.7 µF 0.1 µF 64 µF 64 µF
1.8 nF
2.2 nF
4.7 µH
8.66 K
52.3 k
470pF
232K
10K
52.3K
60.4K
1µF
2K
33nF102K
DNP
Zero Ohm ultra sonic select
0.1µF
3.3
560K
0.1 µF
47µF
6V to 55 V
= 5 V
SiC471, SiC472, SiC473, SiC474
www.vishay.com Vishay Siliconix
S18-0939-Rev. C, 17-Sep-2018 11 Document Number: 75786
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ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000
EXTERNAL COMPONENT SELECTION FOR THE SiC47x
This section explains external component selection for the
SiC47x family of regulators. Component reference
designators in any equation refer to the schematic shown in
Fig. 10.
An excel based calculator is available on the website to
make external component calculation simple. The user
simply needs to enter required operating conditions.
Output Voltage Adjustment
If a different output voltage is needed, simply change the
value of VOUT and solve for R_FB_H based on the following
formula:
where VFB is 0.8 V. R_FB_L should be a maximum of 10 k to
prevent VOUT from drifting at no load.
Switching Frequency Selection
The following equation illustrates the relationship between
frequency, VIN, VOUT, and Rfsw value:
Inductor Selection
In order to determine the inductance, the ripple current must
first be defined. Low inductor values allow for the use of
smaller package sizes but create higher ripple current which
can reduce efficiency. Higher inductor values will reduce the
ripple current and, for a given DC resistance, are more
efficient. However, larger inductance translates directly into
larger packages and higher cost. Cost, size, output ripple,
and efficiency are all used in the selection process.
The ripple current will also set the boundary for power save
operation. The SiC47x will typically enter power save mode
when the load current decreases to 1/2 of the ripple current.
For example, if ripple current is 1.8 A, power save operation
will be active for loads less than 0.9 A. If ripple current is set
at 30 % of maximum load current, power save will typically
start at a load which is 15 % of maximum current.
The inductor value is typically selected to provide ripple
current of 25 % to 50 % of the maximum load current. This
provides an optimal trade-off between cost, efficiency, and
transient performance. During the on-time, voltage across
the inductor is (VIN - VOUT). The equations for determining
inductance are shown below.
and
where, K is the maximum percentage of ripple current. The
designer can quickly make a choice of inductor if the ripple
percentage is decided, usually no more than 30 % however
higher or lower percentages of IOUT can be acceptable
depending on application. This device allows choices larger
than 30 %.
Other than the inductance the DCR and saturation current
parameters are key values. The DCR causes an I2R loss
which will decrease the system efficiency and generate
heat. The saturation current has to be higher than the
maximum output current plus ½ of the ripple current. In an
over current condition the inductor current may be very high.
All this needs to be considered when selecting the inductor.
Output Capacitor Selection
The SiC47x is stable with any type of output capacitors by
choosing the appropriate VRAMP components. This allows
the user to choose the output capacitance based on the
best trade off of board space, cost and application
requirements.
The output capacitors are chosen based upon required ESR
and capacitance. The maximum ESR requirement is
controlled by the output ripple voltage requirement and the
DC tolerance. The output voltage has a DC value that is
equal to the valley of the output ripple plus half of the
peak-to-peak ripple. A change in the output ripple voltage
will lead to a change in DC voltage at the output. The
relationship between output voltage ripple, output
capacitance and ESR of the output capacitor is shown by
the following equation:
(1)
Where VRIPPLE is the maximum allowed output ripple
voltage; IRIPPLE(MAX.) is the maximum inductor ripple current;
fsw is the switching frequency of the converter; Co is the total
output capacitance; ESR is the equivalent series resistance
of the total output capacitors.
In addition to the output ripple voltage requirement, the
output capacitors need to meet transient requirements. A
worst case load release condition (from maximum load to no
load at the exact moment when inductor current is at the
peak) determines the required capacitance. If the load
release is instantaneous (load changes from maximum to
zero within 1 µs), the output capacitor must absorb all the
energy stored in the inductor. The peak voltage on the
capacitor, VPK, under this worst case condition can be
calculated by following equation:
(2)
During the load release time, the voltage across the inductor
is approximately -VOUT. This causes a down-slope or falling
di/dt in the inductor. If the load di/dt is not much faster than
the di/dt of the inductor, then the inductor current will tend
to track the falling load current. This will reduce the excess
inductive energy that must be absorbed by the output
capacitor; therefore a smaller capacitance can be used. The
following can be used to calculate the required capacitance
for a given diLOAD/dt.
R_FB_H
R_FB_L VOUT - VFB

VFB
-----------------------------------------------------
=
Rfsw
VOUT
fsw x 190 x 10 12–

----------------------------------------------------
=
tON
VOUT
VIN x fsw
------------------------
=
LVIN - VOUT
 x tON
IOUT_MAX. x K
--------------------------------------------------
=
VRIPPLE IRIPPLE MAX.
x 1
8 x Co x fsw
---------------------------------ESR+


=
COUT_MIN.
L x IOUT + 1
2
--- x IRIPPLE(MAX.)


2
VPK

2 - VOUT

2
--------------------------------------------------------------------------------
=
SiC471, SiC472, SiC473, SiC474
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S18-0939-Rev. C, 17-Sep-2018 12 Document Number: 75786
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Peak inductor current, ILPK, is shown by the next equation:
The slew rate of load current =
(3)
Based on application requirement, either equation (2) or
equation (3) can be used to calculate the ideal output
capacitance to meet transition requirement. Compare this
calculated capacitance with the result from equation (1) and
choose the larger value to meet both ripple and transition
requirement.
Enable Pin Voltage
The EN pin has an internal 5 M pull down resistor
connected to AGND. In order to enable the device, an
external signal greater than 1.4 V is required. The enable can
also be used to set the minimum VCIN, VIN startup voltage by
connecting a voltage divider between VIN, EN, and PGND. An
automated calculator is available to assist in component
selection.
Current Limit Resistor
The current limit is set by placing a resistor between ILIM and
AGND. The values can be found using the following equation:
Where
•I
OUT_MAX. is desired DC current limit level
•K
LIM is determined by Table 2
Note
• It is suggested that the current limit setting not be higher than
2 times the rated current of the part. Be sure max. current limit
is within the saturation current of the inductor
Input Capacitance
In order to determine the minimum capacitance the input
voltage ripple needs to be specified; VIN_PK-PK 500 mV is a
suitable starting point. This magnitude is determined by the
final application specification. The input current needs to be
determined for the lowest operating input voltage,
The minimum input capacitance can then be found,
If high ESR capacitors are used, it is good practice to also
add low ESR ceramic capacitance. A 4.7 µF ceramic input
capacitance is a suitable starting point.
Note, account for voltage derating of capacitance when
using all ceramic input capacitors.
Efficiency Measurement
Fig. 11 to 39 in the following pages are the efficiency data
for the SiC471, SiC472, SiC473, and SiC474.
The measurements are taken based on the Vishay 6 layers,
2 ounce copper evaluation board.
The inductors used in the measurement are tabulated
below.
TABLE 2 - KLIM VALUE AND RLIM RANGE
PART NUMBER KLIM RLIM MIN. / MAX.
VALUE
SiC471 900K 30K / 900K
SiC472 600K 30K / 600K
SiC473 300K 30K / 420K
SiC474 300K 30K / 300K
ILPK IMAX.
1
2
--- x IRIPPLE(MAX.)
+=
diLOAD
dt
-------------------
COUT_MIN. ILPK x
L x ILPK
VOUT
-------------- - IMAX.
dILOAD
------------------- x dt
2V
PK - VOUT

---------------------------------------------------------------
=
RLIM (k KLIM
IOUT_MAX.
VIN VOUT
–VOUT
2f
sw
VIN
L
------------------------------------------------------
–
----------------------------------------------------------------------------------------
=
TABLE 3 - INDUCTOR VALUES
DEVICE
PART
INDUCTANCE
(μH)
INDUCTOR PART
NUMBER
DCR
(m)
SiC471
3.3 IHLP6767GZER3R3M11 2.79
4.7 IHLP6767GZER4R7M11 3.98
6.8 IHLP6767GZER6R8M11 5.86
8.2 IHLP6767GZER8R2M11 7.71
10 IHLP6767GZER100M11 8.89
SiC472
5.6 IHLP5050FDER5R6M51 8.51
6.8 IHLP5050FDER6R8M51 11.30
8.2 IHLP5050FDER8R2M51 13.20
10 IHLP5050FDER100M51 16.60
15 IHLP5050FDER150M51 24.00
SiC473
10 IHLP5050FDER100M51 16.60
15 IHLP5050FDER150M51 24.00
22 IHLP5050FDER220M51 31.30
SiC474
10 IHLP5050FDER100M51 16.60
15 IHLP5050FDER150M51 24.00
22 IHLP5050FDER220M51 31.30
IVCIN RMS
=
IO x D x 1 D–
1
12
------
VOUT
Lƒ
sw IOUT
-------------------------------------


2
1D–
2
D+
CVIN_MIN. IOUT x D x 1 - D
VIN_PK-PK x fsw
-----------------------------------------
=
SiC471, SiC472, SiC473, SiC474
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S18-0939-Rev. C, 17-Sep-2018 13 Document Number: 75786
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ELECTRICAL CHARACTERISTICS (VIN = 48 V, VOUT = 5 V, fsw = 300 kHz, SiC471 (12 A), unless otherwise noted)
Fig. 11 - SiC471 Efficiency vs. Output Current,
VOUT = 5 V
Fig. 12 - SiC471 Efficiency vs. Output Current,
VOUT = 12 V
Fig. 13 - SiC471 Load Current vs. Case Temperature,
VIN = 48 V, VOUT = 5 V
Fig. 14 - SiC471 Efficiency vs. Output Current - Light Load,
VOUT = 5 V
Fig. 15 - SiC471 Efficiency vs. Output Current - Light Load,
VOUT = 12 V
Fig. 16 - SiC471 Load Current vs. Case Temperature,
VIN = 48 V, VOUT = 12 V
80
82
84
86
88
90
92
94
96
98
100
0123456789101112
Efciency (%)
Output Current, IOUT (A)
VIN = 48 V, L = 4.7 µH
VIN = 24 V, L = 4.7 µH
VIN = 12 V, L = 3.3 µH
VIN = 36 V, L = 4.7 µH
80
82
84
86
88
90
92
94
96
98
100
0123456789101112
Efciency (%)
Output Current, IOUT (A)
VIN = 48 V, L = 10 µH
VIN = 24 V, L = 6.8 µH
VIN = 36 V, L = 8.2 µH
10
100
1000
10000
20
30
40
50
60
70
80
90
100
0123456789101112
Axis Title
1st line
2nd line
2nd line
TC- Case Temperature (°C)
IOUT - Output Current (A)
70
73
76
79
82
85
88
91
94
97
100
0.01 0.1 1
Efciency (%)
Output Current, I
OUT
(A)
V
IN
= 48 V, L = 4.7 µH
V
IN
= 24 V, L = 4.7 µH
V
IN
= 12 V, L = 3.3 µH
V
IN
= 36 V, L = 4.7 µH
70
73
76
79
82
85
88
91
94
97
100
0.01 0.1 1
Efciency (%)
Output Current, IOUT (A)
V
IN
= 48 V, L = 10 µH
V
IN
= 24 V, L = 6.8 µH
V
IN
= 36 V, L = 8.2 µH
10
100
1000
10000
20
30
40
50
60
70
80
90
100
0123456789101112
Axis Title
1st line
2nd line
2nd line
TC- Case Temperature (°C)
IOUT - Output Current (A)
SiC471, SiC472, SiC473, SiC474
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ELECTRICAL CHARACTERISTICS (VIN = 48 V, VOUT = 5 V, fsw = 300 kHz, SiC472 (8 A), unless otherwise noted)
Fig. 17 - SiC472 Efficiency vs. Output Current,
VOUT = 5 V
Fig. 18 - SiC472 Efficiency vs. Output Current,
VOUT = 12 V
Fig. 19 - SiC472 Load Current vs. Case Temperature,
VIN = 48 V, VOUT = 5 V
Fig. 20 - SiC472 Efficiency vs. Output Current - Light Load,
VOUT = 5 V
Fig. 21 - SiC472 Efficiency vs. Output Current - Light Load,
VOUT = 12 V
Fig. 22 - SiC472 Load Current vs. Case Temperature,
VIN = 48 V, VOUT = 12 V
80
82
84
86
88
90
92
94
96
98
100
012345678
Efciency (%)
Output Current, IOUT (A)
V
IN
= 48 V, L = 8.2 µH
V
IN
= 24 V, L = 6.8 µH
V
IN
= 12 V, L = 5.6 µH
V
IN
= 36 V, L = 8.2 µH
80
82
84
86
88
90
92
94
96
98
100
012345678
Efciency (%)
Output Current, IOUT (A)
V
IN
= 48 V, L = 15 µH
V
IN
= 24 V, L = 10 µH
V
IN
= 36 V, L = 15 µH
10
100
1000
10000
20
30
40
50
60
70
80
90
100
012345678
Axis Title
1st line
2nd line
2nd line
TC- Case Temperature (°C)
IOUT - Output Current (A)
70
73
76
79
82
85
88
91
94
97
100
0.01 0.1 1
Efciency (%)
Output Current, IOUT (A)
VIN = 48 V, L = 8.2 µH
VIN = 24 V, L = 6.8 µH
VIN = 12 V, L = 5.6 µH
VIN = 36 V, L = 8.2 µH
70
73
76
79
82
85
88
91
94
97
100
0.01 0.1
Efciency (%)
Output Current, I
OUT
(A)
V
IN
= 48 V, L = 15 µH
V
IN
= 24 V, L = 10 µH
V
IN
= 36 V, L = 15 µH
1
10
100
1000
10000
20
30
40
50
60
70
80
90
100
012345678
Axis Title
1st line
2nd line
2nd line
TC- Case Temperature (°C)
IOUT - Output Current (A)
SiC471, SiC472, SiC473, SiC474
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ELECTRICAL CHARACTERISTICS (VIN = 48 V, VOUT = 5 V, fsw = 300 kHz, SiC473 (5 A), unless otherwise noted)
Fig. 23 - SiC473 Efficiency vs. Output Current,
VOUT = 5 V
Fig. 24 - SiC473 Efficiency vs. Output Current,
VOUT = 12 V
Fig. 25 - SiC473 Load Current vs. Case Temperature,
VIN = 48 V, VOUT = 5 V
Fig. 26 - SiC473 Efficiency vs. Output Current - Light Load,
VOUT = 5 V
Fig. 27 - SiC473 Efficiency vs. Output Current - Light Load,
VOUT = 12 V
Fig. 28 - SiC473 Load Current vs. Case Temperature,
VIN = 48 V, VOUT = 12 V
80
82
84
86
88
90
92
94
96
98
100
0123456
Efciency (%)
Output Current, I
OUT
(A)
VIN = 48 V, L = 15 µH
VIN = 24 V, L = 15 µH
VIN = 12 V, L = 10 µH
VIN = 36 V, L = 15 µH
80
82
84
86
88
90
92
94
96
98
100
0123456
Efciency (%)
Output Current, I
OUT
(A)
V
IN
= 48 V, L = 22 µH
V
IN
= 24 V, L = 15 µH
V
IN
= 36 V, L = 22 µH
10
100
1000
10000
20
30
40
50
60
70
80
90
100
012345
Axis Title
1st line
2nd line
2nd line
TC- Case Temperature (°C)
IOUT - Output Current (A)
70
73
76
79
82
85
88
91
94
97
100
0.01 0.1 1
Efciency (%)
Output Current, I
OUT
(A)
V
IN
= 48 V, L = 15 µH
V
IN
= 24 V, L = 15 uH
V
IN
= 12 V, L = 10 µH
V
IN
= 36 V, L = 15 µH
70
73
76
79
82
85
88
91
94
97
100
0.01 0.1 1
Efciency (%)
Output Current, I
OUT
(A)
V
IN
= 48 V, L = 22 µH
V
IN
= 24 V, L = 15 µH
V
IN
= 36 V, L = 22 µH
10
100
1000
10000
20
30
40
50
60
70
80
90
100
012345
Axis Title
1st line
2nd line
2nd line
TC- Case Temperature (°C)
IOUT - Output Current (A)
SiC471, SiC472, SiC473, SiC474
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ELECTRICAL CHARACTERISTICS (VIN = 48 V, VOUT = 5 V, fsw = 300 kHz, SiC474 (3 A), unless otherwise noted)
Fig. 29 - SiC474 Efficiency vs. Output Current,
VOUT = 5 V
Fig. 30 - SiC474 Efficiency vs. Output Current,
VOUT = 12 V
Fig. 31 - SiC474 Load Current vs. Case Temperature,
VIN = 48 V, VOUT = 5 V
Fig. 32 - SiC474 Efficiency vs. Output Current - Light Load,
VOUT = 5 V
Fig. 33 - SiC474 Efficiency vs. Output Current - Light Load,
VOUT = 12 V
Fig. 34 - SiC474 Load Current vs. Case Temperature,
VIN = 48 V, VOUT = 12 V
80
82
84
86
88
90
92
94
96
98
100
01234
Efciency (%)
Output Current, IOUT (A)
VIN = 48 V, L = 15 µH
VIN = 24 V, L = 15 µH
VIN = 12 V, L = 10 µH
VIN = 36 V, L = 15 µH
80
82
84
86
88
90
92
94
96
98
100
01234
Efciency (%)
Output Current, I
OUT
(A)
V
IN
= 48 V, L = 22 µH
V
IN
= 24 V, L = 15 µH
V
IN
= 36 V, L = 22 µH
10
100
1000
10000
20
30
40
50
60
70
80
90
100
0123
Axis Title
1st line
2nd line
2nd line
TC- Case Temperature (°C)
IOUT - Output Current (A)
70
73
76
79
82
85
88
91
94
97
100
0.01 0.1 1
Efciency (%)
Output Current, I
OUT
(A)
V
IN
= 48 V, L = 15 µH
V
IN
= 24 V, L = 15 µH
V
IN
= 12 V, L = 10 µH
V
IN
= 36 V, L = 15 µH
70
73
76
79
82
85
88
91
94
97
100
0.01 0.1 1
Efciency (%)
Output Current, IOUT (A)
VIN = 48 V, L = 22 µH
VIN = 24 V, L = 15 µH
VIN = 36 V, L = 22 µH
10
100
1000
10000
20
30
40
50
60
70
80
90
100
0123
Axis Title
1st line
2nd line
2nd line
TC- Case Temperature (°C)
IOUT - Output Current (A)
SiC471, SiC472, SiC473, SiC474
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ELECTRICAL CHARACTERISTICS (VIN = 48 V, VOUT = 5 V, fsw = 300 kHz, SiC472 (8 A), unless otherwise noted)
Fig. 35 - SiC471 Efficiency vs. Switching Frequency
Fig. 36 - SiC473 Efficiency vs. Switching Frequency
Fig. 37 - RDS(ON) vs. Temperature
Fig. 38 - SiC472 Efficiency vs. Switching Frequency
Fig. 39 - SiC474 Efficiency vs. Switching Frequency
Fig. 40 - Voltage Reference vs. Temperature
10
100
1000
10000
0.96
0.97
0.98
0.99
1.00
1.01
1.02
1.03
1.04
0 100 200 300 400 500 600 700 800 900 1000
Axis Title
1st line
2nd line
2nd line
Normalized Efficiency
fsw - Switching Frequency (kHz)
10
100
1000
10000
0.96
0.97
0.98
0.99
1.00
1.01
1.02
1.03
1.04
0 100 200 300 400 500 600 700 800 900 1000
Axis Title
1st line
2nd line
2nd line
Normalized Efficiency
fsw - Switching Frequency (kHz)
0.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
-60 -40 -20 0 20 40 60 80 100 120 140
Normalized On-State Resistance, R
DSON
Temperature (°C)
10
100
1000
10000
0.95
0.96
0.97
0.98
0.99
1.00
1.01
1.02
1.03
1.04
0 100 200 300 400 500 600 700 800 900 1000
Axis Title
1st line
2nd line
2nd line
Normalized Efficiency
fsw - Switching Frequency (kHz)
10
100
1000
10000
0.96
0.97
0.98
0.99
1.00
1.01
1.02
1.03
1.04
0 100 200 300 400 500 600 700 800 900 1000
Axis Title
1st line
2nd line
2nd line
Normalized Efficiency
fsw - Switching Frequency (kHz)
792
794
796
798
800
802
804
806
808
-60 -40 -20 0 20 40 60 80 100 120 140
Voltage Reference, VFB (mv)
Temperature (°C)
SiC471, SiC472, SiC473, SiC474
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ELECTRICAL CHARACTERISTICS (VIN = 48 V, VOUT = 5 V, fsw = 300 kHz, SiC472 (8 A), unless otherwise noted)
Fig. 41 - Line Regulation
Fig. 42 - Shutdown Current vs. Input Voltage
Fig. 43 - Input Current vs. Input Voltage
Fig. 44 - Load Regulation
Fig. 45 - Shutdown Current vs. Junction Temperature
Fig. 46 - Input Current vs. Junction Temperature
10
100
1000
10000
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
0 6 12 18 24 30 36 42 48 54 60
Axis Title
1st line
2nd line
2nd line
Line Regulation (%)
VIN - Input Voltage (V)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
5 10152025303540455055
Shutdown Current, I
VCIN_SHDN
+ I
VIN_SHDN
(uA)
Input Voltage, V
CIN
/ V
IN
(V)
140
160
180
200
220
240
260
280
300
5 10152025303540455055
Input Current, IVCIN + IVIN (uA)
Input Voltage, VCIN / VIN (V)
10
100
1000
10000
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
012345678
Axis Title
1st line
2nd line
2nd line
Load Regulation (%)
IOUT - Output Current (A)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
-60 -40 -20 0 20 40 60 80 100 120 140
Shutdown Current, IVCIN_SHDN + IVIN_SHDN (uA)
Temperature (°C)
140
160
180
200
220
240
260
280
300
-60 -40 -20 0 20 40 60 80 100 120 140
Input Current, I
VCIN
+ I
VIN
(uA)
Temperature (°C)
SiC471, SiC472, SiC473, SiC474
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ELECTRICAL CHARACTERISTICS (VIN = 48 V, VOUT = 5 V, fsw = 300 kHz, SiC472 (8 A), unless otherwise noted)
Fig. 47 - EN Logic Threshold vs. Junction Temperature
Fig. 48 - Load Transient (3 A to 6 A), Time = 100 μs/div
Fig. 49 - Start-Up with EN, Time = 1 ms/div
Fig. 50 - EN Current vs. Junction Temperature
Fig. 51 - Line Transient (8 V to 48 V), Time = 10 ms/div
Fig. 52 - Start-up with VIN, Time = 5 ms/div
10
100
1000
10000
1
1.1
1.2
1.3
1.4
1.5
-60 -40 -20 0 20 40 60 80 100 120 140
Axis Title
1st line
2nd line
2nd line
VEN - EN Logic Threshold (V)
T - Temperature (°C)
V
IH_EN
VIL_EN
10
100
1000
10000
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
-60 -40 -20 0 20 40 60 80 100 120 140
Axis Title
1st line
2nd line
2nd line
EN Current, IEN (µA)
T - Temperature (°C)
VEN = 5.0 V
SiC471, SiC472, SiC473, SiC474
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ELECTRICAL CHARACTERISTICS (VIN = 48 V, VOUT = 5 V, fsw = 300 kHz, SiC472 (8 A), unless otherwise noted)
Fig. 53 - Output Ripple 2 A, Time = 5 μs/div
Fig. 54 - Output Ripple PSM, Time = 10 ms/div
Fig. 55 - Output Ripple 300 mA, Time = 5 μs/div
SiC471, SiC472, SiC473, SiC474
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PCB LAYOUT RECOMMENDATIONS
Step 1: VIN/GND Planes and Decoupling
Fig. 56
1. Layout VIN and PGND planes as shown above
2. Ceramic capacitors should be placed between VIN and
PGND, and very close to the device for best decoupling
effect
3. Various ceramic capacitor values and package sizes
should be used to cover entire coupling spectrum
e.g. 1210 and 0603
4. Smaller capacitance values, closer to VIN pin(s), provide
better high frequency response
Step 2: VCIN Pin
Fig. 57
1. VCIN is the input pin for both internal LDO and tON block.
tON varies with input voltage and it is necessary to put a
decoupling capacitor close to this pin
2. The connection can be made through a via and the
capacitor can be placed at bottom layer
Step 3: SW Plane
Fig. 58
1. Connect output inductor to device with large plane to
lower resistance
2. If any snubber network is required, place the
components on the bottom side as shown above
Step 4: VDD/VDRV Input Filter
Fig. 59
1. CVDD cap should be placed between VDD and AGND to
achieve best noise filtering
2. CVDRV cap should be placed close to VDRV and PGND pins
to reduce effects of trace impedance and provide
maximum instantaneous driver current for low side
MOSFET during switching cycle
VIN
VSWH
VIN Plane
PGND Plane
Vcin decouple cap
AGND Plane
PGND Plane
VSWH
Snubber
AGND
P
G
N
D
SiC471, SiC472, SiC473, SiC474
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Step 5: BOOT Resistor and Capacitor Placement
Fig. 60
1. CBOOT and RBOOT need to be placed very close to the
device, between PHASE and BOOT pins
2. In order to reduce parasitic inductance, it is
recommended to use 0402 chip size for the resistor and
the capacitor
Step 6: Signal Routing
Fig. 61
1. Separate the small analog signal from high current path.
As shown above, the high current paths with high dv/dt,
di/dt are placed on the left side of the IC, while the small
control signals are placed on the right side of the IC. All
the components for small analog signal should be
placed closer to IC with minimum trace length
2. IC analog ground (AGND), pin 23, should have a single
connection to PGND. The AGND ground plane connected
to pin 23 helps to keep AGND quiet and improves noise
immunity
3. Feedback signal can be routed through inner layer. Make
sure this signal is far from SW node and shielded by
inner ground layer
4. Ripple injection circuit can be placed next to inductor.
Kelvin connection as shown above is recommended
PGND
AGND
plane
F
B
s
i
g
n
a
l
Ripple
injection
circuit
SiC471, SiC472, SiC473, SiC474
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Step 7: Adding Thermal Relief Vias and Duplicate Power
Path Plane
Fig. 62
1. Thermal relief vias can be added on the VIN and PGND
pads to utilize inner layers for high current and thermal
dissipation
2. To achieve better thermal performance, additional vias
can be placed on VIN and PGND planes. It is also
necessary to duplicate the VIN and ground plane at
bottom layer to maximize the power dissipation
capability of the PCB
3. SW pad is a noise source and it is not recommended to
place vias on this pad
4. 8 mil vias on pads and 10 mil vias on planes are ideal via
sizes. The vias on pad may drain solder during assembly
and cause assembly issues. Please consult with the
assembly house for guideline
Step 8: Ground Layer
Fig. 63
1. It is recommended to make the entire inner layer (next to
top layer) ground plane
2. This ground plane provides shielding between noise
source on top layer and signal trace within inner layer
3. The ground plane can be broken into two sections, PGND
and AGND
VIN Plane
PGND Plane
VSWH
PGND Plane AGND Plane
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Vishay Siliconix maintains worldwide manufacturing capability. Products may be manufactured at one of several qualified locations. Reliability data for Silicon
Technology and Package Reliability represent a composite of all qualified locations. For related documents such as package / tape drawings, part marking, and
reliability data, see www.vishay.com/ppg?75786.
PRODUCT SUMMARY
Part number SiC471 SiC472 SiC473 SiC474
Description
12 A, 4.5 V to 55 V input,
100 kHz to 2 MHz,
synchronous microBUCK
regulator
8 A, 4.5 V to 55 V input,
100 kHz to 2 MHz,
synchronous microBUCK
regulator
5 A, 4.5 V to 55 V input,
100 kHz to 2 MHz,
synchronous microBUCK
regulator
3 A, 4.5 V to 55 V input,
100 kHz to 2 MHz,
synchronous microBUCK
regulator
Input voltage min. (V) 4.5 4.5 4.5 4.5
Input voltage max. (V) 55 55 55 55
Output voltage min. (V) 0.8 0.8 0.8 0.8
Output voltage max. (V) 0.92 x VIN 0.92 x VIN 0.92 x VIN 0.92 x VIN
Continuous current (A) 12 8 5 3
Switch frequency min. (kHz) 100 100 100 100
Switch frequency max. (kHz) 2000 2000 2000 2000
Pre-bias operation (yes / no) Yes Yes Yes Yes
Internal bias reg. (yes / no) Yes Yes Yes Yes
Compensation External External External External
Enable (yes / no) Yes Yes Yes Yes
PGOOD (yes / no) Yes Yes Yes Yes
Over current protection Yes Yes Yes Yes
Protection OVP, OCP, UVP/SCP,
OTP, UVLO
OVP, OCP, UVP/SCP,
OTP, UVLO
OVP, OCP, UVP/SCP,
OTP, UVLO
OVP, OCP, UVP/SCP,
OTP, UVLO
Light load mode Selectable powersave /
ultrasonic
Selectable powersave /
ultrasonic
Selectable powersave /
ultrasonic
Selectable powersave /
ultrasonic
Peak efficiency (%) 98 98 98 98
Package type PowerPAK MLP55-27L PowerPAK MLP55-27L PowerPAK MLP55-27L PowerPAK MLP55-27L
Package size (W, L, H) (mm) 5 x 5 x 0.75 5 x 5 x 0.75 5 x 5 x 0.75 5 x 5 x 0.75
Status code 1111
Product type microBUCK
(step down regulator)
microBUCK
(step down regulator)
microBUCK
(step down regulator)
microBUCK
(step down regulator)
Applications
Computing, consumer,
industrial, healthcare,
networking
Computing, consumer,
industrial, healthcare,
networking
Computing, consumer,
industrial, healthcare,
networking
Computing, consumer,
industrial, healthcare,
networking
Package Information
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PowerPAK® MLP55-27 Case Outline
DIM. MILLIMETERS INCHES
MIN. NOM. MAX. MIN. NOM. MAX.
A (8) 0.70 0.75 0.80 0.027 0.029 0.031
A1 0.00 - 0.05 0.000 - 0.002
A2 0.20 ref. 0.008 ref.
b (4) 0.20 0.25 0.30 0.008 0.010 0.012
b1 0.15 0.20 0.25 0.006 0.008 0.010
D 5.00 BSC 0.197 BSC
e 0.50 BSC 0.020 BSC
e1 0.65 BSC 0.026 BSC
e2 1.00 BSC 0.039 BSC
e3 1.13 BSC 0.044 BSC
E 5.00 BSC 0.197 BSC
L 0.35 0.40 0.45 0.014 0.016 0.018
N (3) 28 28
D2-1 3.25 3.30 3.35 0.128 0.130 0.132
D2-2 0.95 1.00 1.05 0.037 0.039 0.041
D2-3 1.95 2.00 2.05 0.077 0.079 0.081
D2-4 1.37 1.42 1.47 0.054 0.056 0.058
E2-1 0.95 1.00 1.05 0.037 0.039 0.041
E2-2 2.55 2.60 2.65 0.100 0.102 0.104
E2-3 2.55 2.60 2.65 0.100 0.102 0.104
E2-4 1.58 1.63 1.68 0.062 0.064 0.066
F1 0.20 - 0.25 0.008 - 0.010
F2 min. 0.20 min. 0.008
MLP55-27L
(5 mm x 5 mm)
Top view Side view
Bottom view
e3e x 2K7 K8
e x 7K4 K4
(4)
B
A
E
e x 2
K6 K4e x 4
C
0.10 A
C
C
0.10 C0.08
A
B
M
e1
e1
b
b1
7
11
11
19
Pin 1 dot
by marking
2 x A
A1
A2
D
12
1
6
20
277
20
27
D2-2
E2-2 E2-1
K
K3
K1
6
12
19
L
1
ee2 K5K4 e1 x 3
K2
D2-3
D2-4
D2-1
E2-4
E2-3
F1
F2
Package Information
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Notes
(1) Use millimeters as the primary measurement
(2) Dimensioning and tolerances conform to ASME Y14.5M. - 1994
(3) N is the number of terminals
Nd is the number of terminals in x-direction
Ne is the number of terminals in y-direction
(4) Dimension b applies to plated terminal and is measured between 0.20 mm and 0.25 mm from terminal tip
(5) The pin #1 identifier must be existed on the top surface of the package by using indentation mark or other feature of package body
(6) Exact shape and size of this feature is optional
(7) Package warpage max. 0.08 mm
(8) Applied only for terminals
K 0.40 BSC 0.016 BSC
K1 0.70 BSC 0.028 BSC
K2 0.70 BSC 0.028 BSC
K3 0.30 BSC 0.012 BSC
K4 0.75 BSC 0.030 BSC
K5 0.80 BSC 0.0315 BSC
K6 0.60 BSC 0.024 BSC
K7 1.25 BSC 0.049 BSC
K8 0.975 BSC 0.038 BSC
ECN: T18-0594-Rev. C, 03-Dec-2018
DWG: 6056
DIM. MILLIMETERS INCHES
MIN. NOM. MAX. MIN. NOM. MAX.
PAD Pattern
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Recommended Land Pattern
PowerPAK® MLP55-27L
All dimensions in millimeters
Land pattern for MLP55-27L
Component for MLP55-27L
1.25 0.5 x 7 = 3.5 1.25
0.35
0.953.4
0.35
0.95
0.5 0.5
1.52 0.88
0.58
0.5
0.95
0.3
1.1
0.3
2.1
0.3
0.95
0.5
1
6
711
12
19
2027
5
0.75 0.5 1 0.65 x 3 = 1.95 0.8
0.35
0.3
2.7 1.1
0.3
1.73 0.97
0.15
0.6 0.5 x 2 = 1 0.65 0.5 x 4 = 2
0.35
0.75
1.02
0.98 0.65 1.13 0.5 0.5
0.5
5
Legal Disclaimer Notice
www.vishay.com Vishay
Revision: 08-Feb-17 1Document Number: 91000
Disclaimer
ALL PRODUCT, PRODUCT SPECIFICATIONS AND DATA ARE SUBJECT TO CHANGE WITHOUT NOTICE TO IMPROVE
RELIABILITY, FUNCTION OR DESIGN OR OTHERWISE.
Vishay Intertechnology, Inc., its affiliates, agents, and employees, and all persons acting on its or their behalf (collectively,
“Vishay”), disclaim any and all liability for any errors, inaccuracies or incompleteness contained in any datasheet or in any other
disclosure relating to any product.
Vishay makes no warranty, representation or guarantee regarding the suitability of the products for any particular purpose or
the continuing production of any product. To the maximum extent permitted by applicable law, Vishay disclaims (i) any and all
liability arising out of the application or use of any product, (ii) any and all liability, including without limitation special,
consequential or incidental damages, and (iii) any and all implied warranties, including warranties of fitness for particular
purpose, non-infringement and merchantability.
Statements regarding the suitability of products for certain types of applications are based on Vishay’s knowledge of
typical requirements that are often placed on Vishay products in generic applications. Such statements are not binding
statements about the suitability of products for a particular application. It is the customer’s responsibility to validate that a
particular product with the properties described in the product specification is suitable for use in a particular application.
Parameters provided in datasheets and / or specifications may vary in different applications and performance may vary over
time. All operating parameters, including typical parameters, must be validated for each customer application by the customer’s
technical experts. Product specifications do not expand or otherwise modify Vishay’s terms and conditions of purchase,
including but not limited to the warranty expressed therein.
Except as expressly indicated in writing, Vishay products are not designed for use in medical, life-saving, or life-sustaining
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Please contact authorized Vishay personnel to obtain written terms and conditions regarding products designed for
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