sc4510 Semtech Corporation, sc4510 Datasheet

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sc4510

Manufacturer Part Number
sc4510
Description
Sc4510 High-performance Synchronous Buck Controller With Reference Tracking
Manufacturer
Semtech Corporation
Datasheet

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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.
The controller 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.
Revision: Jan 07, 2005
POWER MANAGEMENT
Description
Typical Application Circuit
C8
EXT REF
15V MAX
INT REF
VIN
RTN
SYNC
C10
C4
IN+
C1
C5
C2
SC4510
C11
R2
R3
C12
C6
United States Patent #6,441,597
D1
U1
C13
High Performance Synchronous Buck
Controller With Reference Tracking
1
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Features
Applications
Synchronous buck operation with current sink or
source without loss of regulation
Output can track internal or external reference
Buffered reference output from external reference
Combi-Sense mode lossless current sensing
2.5V to 16V operation with 4.75V minimum V
Direct drive for high side N-channel MOSFETs with
diode and capacitor bootstrap
Undervoltage lockout, Soft Start, Enable and Power
Good functions
Fast transient response with external compensation
Current mode control with transconductance error
amplifier
Programmable oscillator frequency with external sync
Externally referenced buck convertors
DDR memory terminators
Point of use power supplies
R1
C3
R4
R6
C9
Q1
Q2
L1
R5
R7
www.semtech.com
SC4510
0.5V MIN
C7
VOUT
PGOOD
REFOUT
RTN
CC

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sc4510 Summary of contents

Page 1

... 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 VIN ...

Page 2

... Test Conditions No load on GDL and GDH AVCC VIN > 2.5V PVCC VIN > 2.5V VIN AVCC MIN AVCC HYST I SSCHG I SSDIS V ENTH V SSTH 2 SC4510 Maximum -0 (steady state) -0 (for < 10ns @ freq. < 500kHz) -0 ±0.3 -0.3 to AVCC -0 3 -60 to +150 -40 to +125 260 2 Min Typ ...

Page 3

... With respect to V REFOUT REFIN (Greater of the two) I REFOUT Fosc Fosc ROSC = 221K Fosc = 1 MHz Fosc = 300 kHz Fosc = 100 kHz Fosc = 0 MHz Output source mode V CSLIM Output sink mode 10 mV Overdrive t CSDLY 3 SC4510 Min Typ Max 0.4 0.7 2.5 275 375 3 15 0.49 0.5 0.51 0.02 0.3 3.0 + 0 ...

Page 4

... Output under fault Source or sink I GDH Source or sink I GDL C = 1000 pF OUT C = 1000 pF OUT Pin Configuration Temp. Range ( -40°C to +85°C REFIN REFOUT PGOOD AVCC PVCC PGND 4 SC4510 Min Typ Max 2.8 2.2 1.5 0 120 20 20 TOP VIEW REF CS+ 4 ...

Page 5

... Pin for external synchronisation signal input 20 AGND 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. Pin Function + 12% with respect to REFIN voltage. 5 SC4510 www.semtech.com ...

Page 6

... Operating Frequency kHz 2004 Semtech Corp. 1000 900 800 700 600 500 400 300 200 100 700 850 1000 6 SC4510 Operating Frequency vs ROSC 100 200 300 400 500 600 ROSC in kOhm www.semtech.com 700 ...

Page 7

... Temperature (°C) 2004 Semtech Corp. Current Limit vs Temperature 74.50 74.00 73.50 73.00 72.50 72.00 71.50 71.00 -40 -30 -20 - Temperature (°C) Frequency vs Temperature @ ROSC = 220K 300.50 300.00 299.50 299.00 298.50 298.00 297.50 -40 -30 -20 - Temperature (°C) 7 SC4510 www.semtech.com ...

Page 8

... POWER MANAGEMENT Block Diagram 2004 Semtech Corp. 8 SC4510 www.semtech.com ...

Page 9

... POWER MANAGEMENT Application Schematic 2004 Semtech Corp. 9 SC4510 www.semtech.com ...

Page 10

... POWERING THE CONTROLLER Supplies VIN, PVCC and AVCC from the input source are used to power the SC4510. The AVCC and PVCC can be tied to VIN supply or can be from separate source to optimise efficiency. The AVCC supply provides the bias for the oscillator, PWM switcher, voltage feedback, current sense and the Power OK circuitry ...

Page 11

... 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 ...

Page 12

... This branch works with a small signal totem pole (Q3 and Q4) integrated in SC4510 in order to improve the signal-to-noise ratio. The base signals Vbe3 and Vbe4 are designed to closely follow the gate signals Vgs1 and Vgs2, respectively. ...

Page 13

... POWER MANAGEMENT Application Information (Contd.) In peak current mode control as in SC4510, the voltage ripple critical for PWM operation. In fact, the peak- s to-peak value of the voltage ripple across directly affects the signal-to-noise ratio of the PWM Cs operation. In general, smaller V Cs noise ratio and more noise sensitive operation ...

Page 14

... Similar steps and equations apply to the current limit setting and scaling for current sinking mode. OVERCURRENT PROTECTION AND HICCUP MODE In addition to the current limit capabilty, SC4510 provides overcurrent protection in case the convertor output is shorted to ground. If this fault condition happens, the controller senses the output voltage via voltage feedback pin IN- ...

Page 15

... This will improve the transient response to step loads. 2004 Semtech Corp. 5) The SC4510 is best placed over a quiet ground plane area. Avoid pulse currents of the Cin, Q this area. This analog ground plane should be connected to the power ground plane at a “quiet” point near the input capacitor ...

Page 16

... BSC 6.40 BSC .026 BSC 0.65 BSC .024 .030 0.45 0.60 0.75 (.039) (1. 0° 8° 0° 8° .004 0.10 .004 0.10 .008 0. 0. (L1) A DETAIL DIMENSIONS INCHES MILLIMETERS (.222) (5.65) .161 4.10 .026 0.65 .016 0.40 .061 1.55 .283 7.20 SC4510 www.semtech.com ...

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