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SC2446 Datasheet Preview

SC2446 Datasheet

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

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SC2446
Dual-Phase Single or Two Output
Synchronous Step-Dowwwwn.DaCtaoShenett4rUo.collmers
POWER MANAGEMENT
Description
The SC2446 is a high-frequency dual synchronous step-
down switching power supply controller. It provides out-
of-phase high-current output gate drives to all N-chan-
nel MOSFET power stages. The SC2446 operates in syn-
chronous continuous-conduction mode. Both phases are
capable of maintaining regulation with sourcing or sink-
ing load currents, making the SC2446 suitable for gen-
erating both VDDQ and the tracking VTT for DDR applica-
tions.
The SC2446 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 SC2446 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 operate from an
input of at least 4.7V and are capable of regulating out-
puts as low as 0.5V
The step-down controllers in the SC2446 have the pro-
vision to sense a synthesized MOSFET RDS(ON) for cur-
rent-mode control. This sensing scheme (U.S. patent
6,441,597) eliminates the need of the current-sense re-
sistor and is more noise-immune than direct sensing of
the high-side or the low-side MOSFET voltage. Precise cur-
rent-sensing with sense resistor is optional.
Individual soft-start and overload shutdown timer is in-
cluded in each step-down controller. The SC2446 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
‹ 75mV/-110mV maximum current sense voltage
‹ Synthesized MOSFET RDS(ON) current-sensing for
low-cost applications
‹ Optional resistor current-sensing for precise current-
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
‹ Buffered VDDQ/2 output
‹ Programmable frequency up to 1 MHz per phase
‹ External synchronization
‹ Industrial temperature range
‹ 28-lead TSSOP - EDP package
Applications
‹ Telecommunication power supplies
‹ DDR memory power supplies
‹ Graphic power supplies
‹ Servers and base stations
VIN
Figure 1
VO2
C99 C95
+
R79
R81
L11
C96 R75
RCS+
Q21
Q23
CFILTER
RFILTER
C101
R83 C103
C92
D11 D12
R73
C93
PVCC
BST2
GDH2
BST1
GDH1
C94
Q22
R74
L12
R77
RCS-
REF
VIN
SYNC
C106
GDL2
GDL1
Q24
R78
PGND
VPN2
VPN1
CS2+
CS2-
CS1+
CS1-
RCS-
IN2-
COMP2
REFIN
IN1-
COMP1
REF
C104
C102
C105
VIN2
SYNC
SS1/EN1
AGND
Rosc
AVCC
R85
VIN
SS2/EN2 REFOUT
C107
C108
U1
SC2446
C109
CFILTER
RFILTER
R84
R76
C97
RCS+
Dual Independant Outputs
VO1
C98
+
R80
C100
R82
Revision: September 9, 2004
1 U.S. Patent No. 6,441,597, www.semtech.com




Semtech Corporation

SC2446 Datasheet Preview

SC2446 Datasheet

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

No Preview Available !

SC2446
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.
Parameter
Symbol
Maximum Ratings
Units
Supply Voltage For Step-Down Controllers
AVCC, PVCC
-0.3 to 20
V
Input Voltage For the Second Converter
High-Side Driver Supply Voltages
VIN2
V VBST1, BST2
-0.3 to 20
-0.3 to 32 (steady state)
-0.3 to 40
(for <10ns @ freq. < 500kHz)
V
V
VPN
VVPN
-0.3 to 20 (steady state)
-0.3 to 26
(for <10ns @ freq. < 500kHz)
V
IN1-, IN2- Voltages
REF, REFOUT Voltages
REFIN Voltage
COMP1, COMP2 Voltages
CS1+, CS1-, CS2+ and CS2- Voltages
SYNC Voltage
SS1/EN1 AND SS2/EN2 Voltages
Peak Gate Drive Currents
Peak VPN1 and VPN2 Output Currents
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
Electrical Characteristics
VIN1-,VIN2-
VREF ,VREFOUT
VREFIN
V VCOMP1, COMP2
V V V VCS1+, CS1-, CS2+, CS2-
VSYNC
VSS1,VSS2
IGDH1, IGDH2, IGDL1, IGDL2
IVPN1, IVPN2
TA
θJC
θJA
TSTG
TLEAD
TJ
-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
3
100
-40 to 85
13
84
-60 to 150
260
150
V
V
V
V
V
V
V
A
mA
°C
°C/W
°C/W
°C
°C
°C
Unless specified: AVCC = PVCC = VIN2 =12V, VBST1 = VBST2 = 12V, SYNC= 0, ROSC = 51.1k, -40°C < TA = TJ < 85°C
Parameter
Symbol
Conditions
Min
Typ Max Units
Undervoltage Lockout
AVCC Start Threshold
AVCC Start Hysteresis
AVCC Operating Current
AVCC Quiescent Current in UVLO
Channel 1 Error Amplifier
AVCCTH
AVCCHYST
ICC
AVCC Increasing
AVCC= 12V
AVCC = AVCCTH - 0.2V
4.5
0.17
12
1.7
4.7
16
V
V
mA
mA
Non-inverting Input Voltage
Non-inverting Input Line Regulation
Input Offset Voltage
Inverting Input Bias Current
Amplifier Transconductance
Amplifier Open-Loop Gain
Amplifier Unity Gain Bandwidth
Minimum COMP1 Switching Threshold
2004 Semtech Corp.
VIN1+
AVCCTH < AVCC< 15V
IIN1-
GM1
aOL1
VVCSSS11+In=cVreCaS1s-in=g0
2
0.490
0.500
1
-100
260
65
5
2.2
0.510
0.02
±3
-250
V
%/V
mV
nA
µΩ−1
dΒ
ΜΗz
V
www.semtech.com


Part Number SC2446
Description Dual-Phase Single or Two Output Synchronous Step-Down Controller
Maker Semtech Corporation
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SC2446 Datasheet PDF






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