SC2446A Datasheet, PDF(1/27 Page) Semtech Corporation – Dual-Phase, Single or Dual Output Synchronous Step-Down Controller

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SC2446A Datasheet, PDF (1/27 Pages) Semtech Corporation – Dual-Phase, Single or Dual Output Synchronous Step-Down Controller

SC2446A

Dual-Phase, Single or Dual Output

Synchronous Step-Down Controller

POWER MANAGEMENT

Description

The SC2446A is a high-frequency dual synchronous step-

down switching power supply controller. It provides out-

of-phase output gate signals. The SC2446A operates in

synchronous continuous-conduction mode. Both phases

are capable of maintaining regulation with sourcing or

sinking load currents, making the SC2446A suitable for

generating both VDDQ and the tracking VTT for DDR appli-

cations.

The SC2446A employs fixed frequency peak current-

mode control for the ease of frequency compensation

and fast transient response.

The dual-phase step-down controllers of the SC2446A

can be configured to provide two individually controlled

and regulated outputs or a single output with shared

current in each phase. The Step-down controllers oper-

ate from an input of at least 4.7V and are capable of

regulating outputs as low as 0.5V

The step-down controllers in the SC2446A have the pro-

vision to sense inductor RDC voltage drop for current-mode

control. This sensing scheme eliminates the need of the

current-sense resistor and is more noise-immune than

direct sensing of the high-side or the low-side MOSFET

voltage. Precise current-sensing with sense resistor is

optional.

Individual soft-start and overload shutdown timer is in-

cluded in each step-down controller. The SC2446A imple-

ments hiccup overload protection. In two-phase single-

output configuration, the master timer controls the soft-

start and overload shutdown functions of both control-

lers.

Typical Application Circuit

Features

Â 2-Phase synchronous continuous conduction mode

for high efficiency step-down converters

Â Out of phase operation for low input current ripples

Â Output source and sink currents

Â Fixed frequency peak current-mode control

Â 50mV/-75mV maximum current sense voltage

Â Inductive current-sensing for low-cost applications

Â Optional resistor current-sensing for precise cur-

rent-limit

Â Dual outputs or 2-phase single output operation

Â Excellent current sharing between individual phases

Â Wide input voltage range: 4.7V to 16V

Â Individual soft-start, overload shutdown and enable

Â Duty cycle up to 88%

Â 0.5V feedback voltage for low-voltage outputs

Â External reference input for DDR applications

Â Programmable frequency up to 1MHz per phase

Â External synchronization

Â Industrial temperature range

Â 28-lead TSSOP lead free package. This product is

fully WEEE and RoHS compliant

Applications

Â Telecommunication power supplies

Â DDR memory power supplies

Â Graphic power supplies

Â Servers and base stations

V IN (1 2 V )

V IN G N D

VO1

C 74

VO1GND

C 62

R 46

R 13

R CS-6

R 28

Figure 1

Revision: November 9, 2005

R 55

R 49

1 VDDO

U 10

VDDC 13

C 45

10 VO

11 CB

28 VSSO

VI 16

VSSC 9

C 68

R 53

In te gra te d M O S F E T /D rive r

REF OUT (0. 5V)

R 29

C 29

R 47

C 40

VIN

R 45

C72 C73

26 BST1

25 GDH 1

PVCC 23

BST2 19

GDH 2 20

24 GD L1

GD L2 21

22 PGND

27 VPN 1

VPN 2 18

1 CS1+

CS2+ 14

2 CS1-

CS2- 13

4 IN1-

IN2- 12

5 COMP1

COMP2 11

8 REF

REFIN 10

7 AGND

VIN 2 17

3 Rosc

SYNC 6

16 AVCC

SS1/EN 1 28

9 R EFOU T SS2/EN 2 15

C 67

R 52

13 VDDC

VDDO 1

16 VI

9 VSSC

VO 10 C 65

CB 11

VSSO 28

In te gra te d M O S F E T /D rive r

REF OUT (0. 5V)

TP11

C 70

C 71

R 48

C 63

C 64

SC2446A

REF OUT (0. 5V)

R14 C23

R CS-5

VO2

C 75

R 50

VO2GND

R 51

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