SP7663
PowerbloxTM
6A 600KHz Synchronous Step Down Regulator
August 2012
Rev. 2.2.0
GENERAL DESCRIPTION
APPLICATIONS
The SP7663 is a synchronous voltage mode
PWM step down (buck) regulator capable of a
constant output current up to 6 Amps. A wide
5V to 22V single input voltage range allows for
single supply operations from industry
standard 5V, 12V and 18V power rails.
Operations down to 3V are supported with an
additional biasing voltage.
Distributed Power Architectures
Point of Load Converters
Power Supply Modules
FPGAs, DSPs and Processors Supplies
FEATURES
With a 600kHz constant operating frequency
and integrated high and low side switch, the
SP7663 reduces the overall component count
and solution footprint. In addition to a 1%
output setpoint accuracy, this device provides
high efficiency, low ripple and excellent line
and load regulation. An enable function and
soft start feature allow for controlled power up
sequencing implementation.
6A Continuous Current
Built-in current limiting, UVLO, output shortcircuit and over temperature protection insure
safe operation under abnormal operating
conditions.
Type II & III Compensations Support
The SP7663 is offered in a RoHS compliant,
lead free 26-pin 7mmx4mm DFN package.
5V-22V Single Input Voltage Rail
3V-22V Input Voltage with 5V Bias
PWM Voltage Mode Control
600kHz Fixed Synchronous Operations
Low RDSON Power Switches
0.8V Min. Output Voltage – 1% Accuracy
Programmable Soft Start
Over Temperature & Short Circuit
Protection/Auto-Restart
Current Limiting
RoHS Compliant Lead Free 26-Pin DFN
US Patent #6,922,041
TYPICAL APPLICATION DIAGRAM
Fig. 1: SP7663 Application Diagram
Exar Corporation
48720 Kato Road, Fremont CA 94538, USA
www.exar.com
Tel. +1 510 668-7000 – Fax. +1 510 668-7001
SP7663
PowerbloxTM
6A 600KHz Synchronous Step Down Regulator
ABSOLUTE MAXIMUM RATINGS
OPERATING RATINGS
These are stress ratings only and functional operation of
the device at these ratings or any other above those
indicated in the operation sections of the specifications
below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may affect
reliability.
Input Voltage Range VCC .............................. 4.5V to 5.5V
Input Voltage Range VIN .................................. 3V to 22V
Junction Temperature Range ....................-40°C to 125°C
Thermal Resistance θJC ........................................ 5°C/W
Thermal Resistance θJA ...................................... 36°C/W
VCC ...................................................................... 7.0V
VIN ........................................................................ 25V
BST ...................................................................... 30V
LX-BST..................................................... -0.3V to 7.0V
LX ............................................................... -1V to 30V
All other pins ................................... -0.3V to (VCC+0.3)V
Storage Temperature .............................. -65°C to 150°C
Power Dissipation .....................Internally Limited via OTP
Lead Temperature (Soldering, 10 sec).................... 300°C
ESD Rating (HBM - Human Body Model) ..........................
LX, VINP, PGND................................................... 400V
All other pins ....................................................... 2kV
ELECTRICAL SPECIFICATIONS
Specifications with standard type are for an Operating Junction Temperature of TJ = 25°C only; limits applying over the full
Operating Junction Temperature range are denoted by a “•”. Minimum and Maximum limits are guaranteed through test,
design, or statistical correlation. Typical values represent the most likely parametric norm at T J = 25°C, and are provided for
reference purposes only. Unless otherwise indicated, 4.5V < VCC < 5.5V, 3V < VIN < 22V, UVIN = 3V, CVCC = 1µF, CCOMP =
0.1µF, CSS = 50nF.
Parameter
Min.
Typ.
Max.
Units
VIN Supply Current
(No switching)
1.5
3.0
mA
VIN Supply Current
(Switching)
8
20
mA
BST Supply Current
(No switching)
0.2
0.4
mA
3
6
mA
Conditions
Quiescent Current
BST Supply Current (switching)
•
VFB= 0.9V
•
VFB= 0.9V
Protection: UVLO
VCC UVLO Start Threshold
VCC UVLO Hysteresis
4.00
4.25
4.5
V
•
300
mV
•
100
200
UVIN Start Threshold
2.30
2.50
2.65
V
•
UVIN Hysteresis
200
300
400
mV
•
150
µA
•
UVIN Input Current
UVIN=3.0V
Error Amplifier Reference
Error Amplifier Reference
0.792
0.800
0.808
V
Error Amplifier Reference Over
Line
0.784
0.800
0.816
V
•
70
150
230
µA
•
VFB=0.9V, COMP=0.9V
-230
-150
-70
µA
•
VFB=0.9V, COMP=0.9V
VFB Input Bias Current
50
200
nA
•
VFB=0.8V
COMP Clamp
3.5
3.8
V
COMP Sink Current
COMP Source Current
COMP Clamp Temp.
Coefficient
© 2012 Exar Corporation
3.2
-2.0
2X Gain Config., Measure V FB; VCC=5V
VFB=0.7V, TA=25°C
mV/°C
2/18
Rev. 2.2.0
SP7663
PowerbloxTM
6A 600KHz Synchronous Step Down Regulator
Parameter
Min.
Typ.
Max.
5.3
Units
Conditions
VCC Linear Regulator
VCC output Voltage
Dropout Voltage
•
VIN=6 to 23V, ILOAD=0mA to 30mA
•
VIN=5V, ILOAD=20mA
mV
•
VIN-VOUT=Dropout voltage when VCC
regulated drops by 2%, IV CC=30mA
1.20
V
•
2.3
V
•
4.7
5.0
4.51
4.73
250
500
750
0.80
1.00
1.7
2.0
V
Control Loop
Ramp Amplitude
RAMP Offset
Ramp offset Temperature
Coefficient
-2
GH Minimum Pulse Width
150
Maximum Controllable Duty
Ratio
Maximum Duty Ratio
92
mV/°C
•
180
97
100
%
•
%
•
Valid for 20 cycles
600
690
KHz
510
Soft-start, Short Circuit, Current Limit and Thermal Protection
•
SS Charge Current
-16
-10
-4
µA
•
SS Discharge Current
1.0
2.0
3.0
mA
•
Short Circuit Threshold Voltage
0.2
0.25
0.3
V
•
Hiccup Timeout
85
110
135
ms
•
Overcurrent Threshold Voltage
54
60
66
mV
ISP, ISN Common Mode Range
0
3.6
V
155
°C
Guaranteed by design
°C
Thermal recovery, decreasing
temperature
Oscillator Frequency
Thermal Shutdown Temperature
135
Thermal Hysteresis
145
10
Fault Present, SS=0.2V
VFB=0.5V
Measured ISP - ISN
Output Power Stage
High Side Switch RDSON
21
25
m
VGS=4.5V, IDRAIN=5A, TA=25°C
Synchronous Low Side Switch
RDSON
21
25
m
VGS=4.5V, IDRAIN=5A, TA=25°C
Maximum Output Current
© 2012 Exar Corporation
A
6
3/18
•
Rev. 2.2.0
SP7663
PowerbloxTM
6A 600KHz Synchronous Step Down Regulator
BLOCK DIAGRAM
Fig. 2: SP7663 Block Diagram (Exar’s SP6136 controller based)
PIN ASSIGNMENT
Fig. 3: SP7663 Pin Assignment
© 2012 Exar Corporation
4/18
Rev. 2.2.0
SP7663
PowerbloxTM
6A 600KHz Synchronous Step Down Regulator
PIN DESCRIPTION
Name
Pin Number
Description
PGND
1-4
GND
5,9,19,20
Ground Pin. The control circuitry of the IC and lower power driver are referenced to this
pin. Return separately from other ground traces to the (-) terminal of COUT.
VFB
6
Feedback Voltage and Short Circuit Detection pin. It is the inverting input of the Error
Amplifier and serves as the output voltage feedback point for the Buck Converter. The
output voltage is sensed and can be adjusted through an external resistor divider.
Whenever VFB drops 0.25V below the positive reference, a short circuit fault is detected
and the IC enters hiccup mode.
COMP
7
Output of the Error Amplifier. It is internally connected to the inverting input of the
PWM comparator. An optimal filter combination is chosen and connected to this pin and
either ground or VFB to stabilize the voltage mode loop.
SS
8
Soft Start. Connect an external capacitor between SS and GND to set the soft start rate
based on the 10μA source current. The SS pin is held low via a 1mA (min) current
during all fault conditions.
ISN
10
Current sense negative input. Rail-to-rail input for over current detection.
ISP
11
Current sense positive input. Rail-to-rail input for over current detection.
SWN
12
Lower supply rail for the GH high-side gate driver. Connect this pin to the switching
node as close as possible to pins 23- 27. Do not connect this pin to pins 14 – 16.
VINP
13
Input connection to the high side N-channel MOSFET.
LX
14-16, 23-26
BST
17
High side driver supply pin. Connect BST to the external boost diode and capacitor as
shown in the Typical Application Circuit on page 1. The high side driver is connected
between BST pin and SWN pin.
VIN
18
VIN connection for internal LDO and PWM Controller.
UVIN
21
UVLO input for VIN voltage. Connect a resistor divider between V IN and UVIN to set
minimum operating voltage. Use resistor values below 20kΩ to override internal resistor
divider.
VCC
22
Output of internal regulator. May be externally biased if V IN < 5V.
Ground connection for the synchronous rectifier.
Connect an inductor between this pin and V OUT.
ORDERING INFORMATION
Part Number
SP7663ER-L
SP7663ER-L/TR
SP7663EB
Junction
Temperature
Range
Marking
SP7663ER
YYWWL
X
SP7663ER
YYWWL
-40°C≤TJ≤+125°C
X
SP7663 Evaluation Board
-40°C≤TJ≤+125°C
Package
Packing
Quantity
26-pin DFN
Bulk
Lead Free
26-pin DFN
3K/Tape & Reel
Lead Free
Note 1
Note 2
“YY” = Year – “WW” = Work Week – “X” = Lot Number
© 2012 Exar Corporation
5/18
Rev. 2.2.0
SP7663
PowerbloxTM
6A 600KHz Synchronous Step Down Regulator
TYPICAL PERFORMANCE CHARACTERISTICS
All data taken at TJ = 25°C, unless otherwise specified - Schematic and BOM from Application Information section of this
datasheet.
Fig. 4: Output Ripple, No Load
Fig. 5: Output Ripple, IOUT=6A
Fig. 6: Startup Response, No Load
Fig. 7: Startup Response, IOUT=6A
Fig. 8: Load Step Response, IOUT=3A-6A
Fig. 9: Load Step Response, IOUT=0A-6A
© 2012 Exar Corporation
6/18
Rev. 2.2.0
SP7663
PowerbloxTM
6A 600KHz Synchronous Step Down Regulator
Fig. 10: Output Current Limit Response
Fig. 11: OCP Hiccup Response Time Dead Short
Fig. 12: Efficiency versus IOUT, VIN=16V
Fig. 13: Efficiency versus IOUT, VIN=12V
Fig. 14: Efficiency versus IOUT, VIN=5V
© 2012 Exar Corporation
7/18
Rev. 2.2.0
SP7663
PowerbloxTM
6A 600KHz Synchronous Step Down Regulator
THEORY OF OPERATION
SOFT START
“Soft Start” is achieved when a power converter ramps up the output voltage while
controlling the magnitude of the input supply
source current. In a modern step down
converter, ramping up the positive terminal of
the error amplifier controls soft start. As a
result, excess source current can be defined as
the current required to charge the output
capacitor.
GENERAL OVERVIEW
The SP7663 is a fixed frequency, voltage
mode, synchronous PWM regulator optimized
for high efficiency. The part has been
specifically
designed
for
single
supply
operation from a 5.5V to 22V input.
The heart of the SP7663 is a wide bandwidth
transconductance
amplifier
designed
to
accommodate
Type
II
and
Type
III
compensation schemes. A precision 0.8V
reference, present on the positive terminal of
the error amplifier, permits the programming
of the output voltage down to 0.8V via the VFB
pin. The output of the error amplifier, COMP, is
compared to a 1.1V peak-to-peak ramp, which
is responsible for trailing edge PWM control.
This voltage ramp and PWM control logic are
governed by the internal oscillator that
accurately sets the PWM frequency to 600kHz.
The SP7663 provides the user with the option
to program the soft start rate by tying a
capacitor from the SS pin to GND. The
selection of this capacitor is based on the
10μA pull up current present at the SS pin and
the 0.8V reference voltage. Therefore, the
excess source can be redefined as:
The SP7663 contains two unique control
features that are very powerful in distributed
applications. First, non-synchronous driver
control is enabled during startup, to prohibit
the low side switch from pulling down the
output until the high side switch has
attempted to turn on. Second, a 100% duty
cycle timeout ensures that the low side switch
is periodically enhanced during extended
periods at 100% duty cycle. This guarantees
the synchronized refreshing of the BST
capacitor during very large duty ratios.
UNDER VOLTAGE LOCK OUT (UVLO)
The SP7663 has two separate UVLO
comparators to monitor the bias (Vcc) and
Input (VIN) voltages independently. The Vcc
UVLO is internally set to 4.25V. The Vin UVLO
is programmable through UVIN pin. When
UVIN pin is greater than 2.5V the SP7663 is
permitted to start up pending the removal of
all other faults. A pair of internal resistors is
connected to UVIN as shown in Figure 16.
The SP7663 also contains a number of
valuable protection features. Programmable
VIN UVLO allows the user to set the exact
value at which the conversion voltage can
safely begin down-conversion, and an internal
VCC UVLO which ensures that the controller
itself has enough voltage to properly operate.
Other protection features include thermal
shutdown and short-circuit detection. In the
event that either a thermal, short-circuit, or
UVLO fault is detected, the SP7663 is forced
into an idle state where the output drivers are
held off for a finite period before a restart is
attempted.
© 2012 Exar Corporation
Fig. 15: Internal and External Bias of UVIN
Therefore without external biasing the VIN
start threshold is 9.5V. A small capacitor may
be required between UVIN and GND to filter
8/18
Rev. 2.2.0
SP7663
PowerbloxTM
6A 600KHz Synchronous Step Down Regulator
out noise. For applications with V IN of 5V or
3.3V, connect UVIN directly to VIN. To program
the VIN start threshold, use a pair of external
resistors as shown. If external resistors are an
order of magnitude smaller than internal
resistors, then the VIN start threshold is given
by:
Fig. 16: Over Current Detection Circuit
For example, if it is required to have a V IN
start threshold of 7V, then let R7 = 5kΩ and
using the VIN start threshold equation we get
R6 = 9.09kΩ.
Inputs
to
an
over-current
detection
comparator, set to trigger at 60mV nominal,
are connected to the inductor as shown. Since
the average voltage sensed by the comparator
THERMAL AND SHORT-CIRCUIT PROTECTION
is equal to the product of inductor current and
inductor DC resistance (DCR), then:
Because the SP7663 is designed to drive large
output current, there is a chance that the
power converter will become too hot.
Therefore, an internal thermal shutdown
(145°C) has been included to prevent the IC
from malfunctioning at extreme temperatures.
Solving this equation for the specific inductor
in circuit 1, IMAX=9.2A. When IMAX is reached, a
120ms time-out is initiated, during which top
and bottom drivers are turned off. Following
the time-out, a restart is attempted. If the
fault condition persists, then the time-out is
repeated (referred to as hiccup).
A short-circuit detection comparator has also
been included in the SP7663 to protect against
an accidental short at the output of the power
converter.
This
comparator
constantly
monitors the positive and negative terminals
of the error amplifier, and if the VFB pin falls
more than 250mV (typical) below the positive
reference, a short-circuit fault is set. Because
the SS pin overrides the internal 0.8V
reference during soft start, the SP7663 is
capable of detecting short-circuit faults
throughout the duration of soft start as well as
in regular operation.
Increasing the Current Limit
If it is desired to set IMAX > (60mV/DCR) (in
this case larger than 14.6A), then a resistor R9
should be added as shown in Figure 18. R9
forms a resistor divider and reduces the
voltage seen by the comparator.
Since
OVER-CURRENT PROTECTION
The Over-current protection feature can only
be used on output voltages ≤ 3.3 volts. It is
limited by the common mode rating of the opamp used to sense the voltage across the
inductor.
Over-current
is
detected
by
monitoring a differential voltage across the
output inductor as shown in the Figure 16.
© 2012 Exar Corporation
Solving for R9 we get:
As an example: if desired IMAX is 9A, then
R9 = 26.4kΩ.
9/18
Rev. 2.2.0
SP7663
PowerbloxTM
6A 600KHz Synchronous Step Down Regulator
In the event of UVLO fault, the SP7663
remains in this idle state until the UVLO fault
is removed. Upon the detection of a thermal or
short-circuit fault, an internal 120ms timer is
activated. In the event of a short-circuit fault,
a restart is attempted immediately after the
120ms timeout expires. Whereas, when a
thermal fault is detected the 100ms delay
continuously recycles and a restart cannot be
attempted until the thermal fault is removed
and the timer expires.
Fig. 17: Over Current Detection Circuit
for IMAX>60mV/DCR
Decreasing the Current Limit
ERROR AMPLIFIER AND VOLTAGE LOOP
If it is required to set IMAX