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PDF SC4510 Data sheet ( Hoja de datos )
| Número de pieza | SC4510 | |
| Descripción | High Performance Synchronous Buck Controller | |
| Fabricantes | Semtech Corporation | |
| Logotipo |  |
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POWER MANAGEMENT
SC4510
High Performance Synchronous Buck
Controller With Reference Tracking
Description
Features
The SC4510 can be configured as a synchronous buck
convertor capable of sourcing and sinking current from load
without losing output regulation. The output can be set to
track an internal reference or an external voltage. The
actual reference used by the error amplifier is buffered
and brought out as a reference. It is the ideal choice for
externally referenced or tracking buck convertors such as
those for DDR memory applications.
www.DataTShheeect4oUn.ctoromller is also designed for point of use DC-DC
convertors with 2.5-16V power sources with a Vcc of 4.5V
or higher. Soft start, current limit, programmable oscillator
and external compensation functions are provided to
ensure high degree of integration and low external
component count. Semetch’s patented Combi-Sense™
technique is utilised for lossless current sening and
maximising efficiency. Both high and low side MOSFET
drivers are built in and rated for substantial peak currents
to minimise switching losses. The SC4510 is offered in a
space saving TSSOP-20 package.
Typical Application Circuit
u Synchronous buck operation with current sink or
source without loss of regulation
u Output can track internal or external reference
u Buffered reference output from external reference
u Combi-Sense mode lossless current sensing
u 2.5V to 16V operation with 4.75V minimum VCC
u Direct drive for high side N-channel MOSFETs with
diode and capacitor bootstrap
u Undervoltage lockout, Soft Start, Enable and Power
Good functions
u Fast transient response with external compensation
u Current mode control with transconductance error
amplifier
u Programmable oscillator frequency with external sync
Applications
u Externally referenced buck convertors
u DDR memory terminators
u Point of use power supplies
VIN
15V MAX
RTN
C1
C2
D1
C4 C5
SYNC
R2 R3 C6
Q1
R1
L1
VOUT
C3
0.5V MIN
Q2
R4
C7
RTN
SC4510
C8
INT REF
IN+
EXT REF
C10
C11 C12
U1
C13
R5
R6
R7
C9
PGOOD
REFOUT
Revision: Jan 07, 2005
United States Patent #6,441,597
1
www.semtech.com
1 page  
SC4510
POWER MANAGEMENT
Pin Descriptions
Pin #
1
Pin Name
REF
Internal 0.5V bandgap reference
Pin Function
2 REFIN
3 REFOUT
4
www.DataSheet4U.com
5
CS+
CS-
6 PGOOD
7 AVCC
8 PVCC
9 GDL
10 PGND
11 GDH
12 BST
13 VPN
14 VIN
15 SS/EN
16 ROSC
17 IN-
18 COMP
19 SYNC
20 AGND
Non inverting input of the error amplifier. Can be connected to REF pin or an external voltage
such as VDDQ/2. Maximum input range is 3V
Buffered reference output fro external use. Tracks the REFIN voltage
Current sense input +ve
Current sense input -ve. Typically connected to the VOUT end of the output inductor.
Power Good output signal. Open collector output goes low under fault and sinks up to 5 mA.
Monitors the output at thresholds of + 12% with respect to REFIN voltage.
Supply voltage for internal analog circuits.
Supply voltage for output drivers. Bypass with a large ceramic capacitor to PGND.
Gate drive output for the low side N-Channel MOSFET.
Power ground for returning the drive currents.
Gate drive output for the high side N-Channel MOSFET.
Boost capacitor connection for the high side gate drive.
Connect an external capacitor and a diode as shown in the Typical Application Circuit.
Virtual Phase Node. Auxiliary pin used for virtual current sense.Connect an RC between this
pin and the VOUT end of the output inductor to sense the integrated current feedback signal.
Input supply for the virtual current sense circuit.
This should be at the same potential as the drain of the high side power MOSFET.
Soft Start and Enable pin. Grounding the pin shuts down the controller. Connect a capacitor to
soft start the output.The output will start switching when the SS pin voltage goes above 0.5V.
Connect a resistor to AGND to program the oscillator frequency.
Inverting feedback input for the error amplifier. Follows the reference input provided at the
REFIN pin. Maximum voltage range is 3V.
Error amplifier output for compensation.
Pin for external synchronisation signal input
Analog signal ground. Return the ground connections of noise sensitive components such as
ROSC, soft start capacitor, sync signal, feedback resistor chain and feedback compensation
components separately to this pin.
© 2004 Semtech Corp.
5
www.semtech.com
5 Page 
POWER MANAGEMENT
Functional Description
Alternately if an external 12V supply is available it can be
directly connected between BST and GND. The actual gate
to source voltage of the upper Mosfet will then be
approximately be equal to (12V - VIN). This technique is
useful if the input voltage is 5V but a 12V supply is also
available in the system.
POWER GOOD MONITOR
The PGOOD circuitry monitors the FB input of the convertor
www.DataeSrhreoert4aUm.cpomlifier. If the voltage on this input goes above +12%
or below -12% of the REFIN voltage the PGOOD pin is pulled
low. The PGOOD is an open drain output and can sink up
to 5 mA. The PGOOD pin is held low during the startup
sequence.
ERROR AMPLIFIER
The SC4510 is a current mode controller and operates by
matching the peak of the sensed inductor current to the
output of the voltage error amplifier. The error amplifier is
transconductance type and should be compensated
accordingly. It has a transconductance gain of 275 µΩ−1
in the source mode. Current is sensed losslessly by taking
the weighted average of both the MOSFET drops and adding
it to the DC voltage drop across the inductor. More
information on this patented Combi Sense technique is
provided in the next section.
Current mode controllers are inherently unstable at duty
ratios above 50% and need some form of slope
compensation to operate correctly. This slope
compensation is built into the architecture of SC4510 where
a portion of the ramp is internally added to the current
sense signal. The amount of added ramp is optimised and
varies with the operating duty cycle. Larger duty ratios result
in larger ramps being added to the current sense signal.
Note that the uncorrected current signal is used for
overcurrent comparator. The current limit point is
unaffected by the slope compensation.
© 2004 Semtech Corp.
11
SC4510
www.semtech.com
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet SC4510.PDF ] | |
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