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Semtech Corporation

SC2446A Datasheet Preview

SC2446A Datasheet

Dual-Phase Single or Two Output Synchronous Step-Down Controller

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SC2446A
Dual-Phase, Single or Dual Output
Synchronous Step-Dwowww.DnataCShoeent4tUr.coomller
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
‹ 2-Phase synchronous continuous conduction mode
for high efficiency step-down converters
‹ Out of phase operation for low input current ripples
‹ Output source and sink currents
‹ Fixed frequency peak current-mode control
‹ 50mV/-75mV maximum current sense voltage
‹ Inductive current-sensing for low-cost applications
‹ Optional resistor current-sensing for precise cur-
rent-limit
‹ Dual outputs or 2-phase single output operation
‹ Excellent current sharing between individual phases
‹ Wide input voltage range: 4.7V to 16V
‹ Individual soft-start, overload shutdown and enable
‹ Duty cycle up to 88%
‹ 0.5V feedback voltage for low-voltage outputs
‹ External reference input for DDR applications
‹ Programmable frequency up to 1MHz per phase
‹ External synchronization
‹ Industrial temperature range
‹ 28-lead TSSOP lead free package. This product is
fully WEEE and RoHS compliant
Applications
‹ Telecommunication power supplies
‹ DDR memory power supplies
‹ Graphic power supplies
‹ Servers and base stations
V IN (1 2 V )
V IN G N D
VO1
C 74
VO1GND
L6
C 62
R 13
R CS-6
R 46
R 28
Figure 1
Revision: November 9, 2005
C6
R 55
R49 C7
1 VDDO
U 10
VDDC 13
C 45 10 VO
11 CB
28 VSSO
VI 16
VSSC 9
In te gra te d M O S F E T /D rive r
C 68
R 53
0
REF OUT (0. 5V)
R 29
C 29
C 40
VIN
R 47
R 45
C72 C73
26 BST1
25 GDH 1
PVCC
B ST2
GDH 2
23
19
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
0
U9
13 VDDC
VDDO 1
16 VI
9 VSSC
VO 10
CB 11
VSSO 28
C 65
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
U3
SC2446A
REF OUT (0. 5V)
L5
R14 C23
R CS-5
1
VO2
C 75
R 50
VO2GND
R 51
www.semtech.com




Semtech Corporation

SC2446A Datasheet Preview

SC2446A Datasheet

Dual-Phase Single or Two Output Synchronous Step-Down Controller

No Preview Available !

SC2446A
POWER MANAGEMENT
www.DataSheet4U.com
Absolute Maximum Rating
Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specified
in the Electrical Characteristics section is not implied. Exposure to Absolute Maximum rated conditions for extended periods of time may affect device
reliability.
Parameter
Symbol
Maximum Ratings Units
Supply Voltage
AVCC
-0.3 to 16
V
Gate Outputs GDH1, GDH2, GDL1, GDL2 voltages
VGDH1, VGDH2,VGDL1, VGDL2
-0.3 to 6
V
IN1-, IN2- Voltages
VIN1-,VIN2-
REFOUT Voltages
VREF ,VREFOUT
REF, REFIN Voltage
COMP1, COMP2 Voltages
CS1+, CS1-, CS2+ and CS2- Voltages
VREFIN
V VCOMP1, COMP2
V V V VCS1+, CS1-, CS2+, CS2-
SYNC Voltage
SS1/EN1 AND SS2/EN2 Voltages
Ambient Temperature Range
Thermal Resistance Junction to Case (TSSOP-28)
Thermal Resistance Junction to Ambient (TSSOP-28)
Storage Temperature Range
Lead Temperature (Soldering) 10 sec
Maximum Junction Temperature
VSYNC
VSS1,VSS2
TA
θJC
θJA
TSTG
TLEAD
TJ
Electrical Characteristics
Unless specified: AVCC = 12V, SYNC = 0, ROSC = 51.1k, -40°C < TA = TJ < 125°C
Parameter
Symbol
Conditions
Min
-0.3 to AVCC+0.3
-0.3 to 6
-0.3 to AVCC+0.3
-0.3 to AVCC+0.3
-0.3 to AVCC+0.3
-0.3 to AVCC+0.3
-0.3 to 6
-40 to 125
13
84
-60 to 150
260
150
Typ Max
V
V
V
V
V
V
V
°C
°C/W
°C/W
°C
°C
°C
Units
Undervoltage Lockout
AVCC Start Threshold
AVCC Start Hysteresis
AVCC Operating Current
AVCC Quiescent Current in UVLO
Channel 1 Error Amplifier
AVCCTH AVCC Increasing
AVCCHYST
ICC AVCC= 12V
AVCC = AVCCTH - 0.2V
4.5 4.7
V
0.2 V
8 15 mA
2.5 mA
Input Common-Mode Voltage Range
(Note 1)
0 3V
Inverting Input Voltage Range
(Note 1)
0
AVCC
V
Input Offset Voltage
0 ~ 70° C
1 ±3 mV
Non-Inverting Input Bias Current
Inverting Input Bias Current
Amplifier Transconductance
Amplifier Open-Loop Gain
Amplifier Unity Gain Bandwidth
IREF
IIN1-
GM1
aOL1
-100
-100
260
65
5
-250
-250
nA
nA
µΩ−1
dΒ
MHz
Minimum COMP1 Switching Threshold
VVCSSS11+In=crVeCaSs1-in=g0
2.2 V
2005 Semtech Corp.
2
www.semtech.com


Part Number SC2446A
Description Dual-Phase Single or Two Output Synchronous Step-Down Controller
Maker Semtech Corporation
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SC2446A Datasheet PDF






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