SC2434 Datasheet, PDF (1/19 Pages) Semtech Corporation – TriPhase Current Mode Controller with Power Good

SC2434
TriPhase Current Mode Controller
with Power Good
POWER MANAGEMENT
Description
The SC2434, a tri-phase, current mode controller is
designed to work with Semtech smart synchronous
drivers, such as the SC1205, SC1206, and SC1207 to
provide the DC/DC converter solution for the most
demanding Microprocessor applications. Input current
sensing is used to guarantee precision phase to phase
current matching using a single sense resistor on the
input power line. This topology reduces the power loss
and complexity associated with output current sense
methods. Multi phase operation allows significant
reduction in input/output ripple while enhancing
transient response. Two or three phase operation is
selectable. The DAC step size and range are program-
mable with external components thus allowing compliance
with new and emerging VID ranges. A novel approach
implements active droop to minimize output capacitors
during load transients.
Typical Application Circuit
Features
! 12V input
! Input sensing current mode control
! Selectable 2 or 3 phase operation
! Precision, pulse by pulse phase current matching
! Active drooping allows for best transient response
! Programmable internal oscillator to 1.5 MHz
! Programmable DAC step size/offset allows compli-
ance with VRM9.0 and VRM9.2
! VID 11111 Inhibit (No CPU)
! Externally programmable soft-start
! 0% minimum duty cycle improves transient
response
! Cycle by cycle current limiting plus hiccup
! Power good signal
Applications
! Intel Pentium-4 microprocessors
! High performance desktop systems
+12V_ATX
L1
R1 3m
+12V
600nH
+
+
+
C1
C2
C3
2200uF/16v 2200uF/16v 2200uF/16v
C5
4.7uF
C6
4.7uF
VCCVID_PWRGD(Open Collector Input)
R29
100
VID4
VID3
VID2
VID1
VID0
+5V_ATX
+5V
V_PULL_UP
R13
5.1K
PWR_GOOD
C29
100nF
R_DRP
187K
R_COMP
75K
C_COMP
18pF
R3
2R2
C8
1uF
C15
C16
1uF
4.7uF
U2
1 _VID4
VCC ²⁰
2 _VID3
BGOUT ¹⁹
3 _VID2
OUT1 ¹⁸
4 _VID1
OUT2 ¹⁷
5
VID0
6
PGIN
16
OUT3
15
PC
7 _ERROUT
AGND ¹⁴
8 _PGOUT
OC- ¹³
9 _FB
OC+ ¹²
10
11
OSCREF DACREF
SC2434
R_OSC
31.6K
R_DAC
37.4K
R_OS
46.4K
R_FB
R19
R20
750
1K
10K
R5
20
Differential
Pair
R8
NO POP
C13
10nF
R2
2R2
R9
2R2
D1
1N4148
C4
1uF
C75 0.33uF
M1
L2
1
8
2 ^{DRN PGND} 7
3
4
TG
BST
CO
BG
VS
EN
6
5
U1
SC1205
R4
1R
D4
1N4148
M2
C9
1nF
600nH
R6
1
SM/R_1206
C11
2.2nF
C12 1uF
+12V
D2
1N4148
C17
1uF
C76 0.33uF
M3
L3
R10
1
2
DRN PGND
8
7
3
4
TG
BST
BG
VS
6
5
CO
EN
U3
SC1205
1R
D5
1N4148
M4
C22
1nF
600nH
R11
1
SM/R_1206
C23
2.2nF
C24 1uF
R15
1K
C31
470pF
+5V
R14
2R2
+12V
D3
1N4148
C27
1uF
C77 0.33uF
M5
L4
1
8
2
3
DRN PGND
TG
BG
7
6
4
BST
CO
VS
EN
5
U4
SC1205
R16
1R
D6
1N4148
M6
C33
1nF
600nH
R17
1
SM/R_1206
C34
2.2nF
C35 1uF
Differential
Pair
AGND
VOUT
C7
1500uF/6.3V
C10
1500uF/6.3V
C14
1500uF/6.3V
C18
1500uF/6.3V
C19
1500uF/6.3V
C20
1500uF/6.3V
C21
1500uF/6.3V
C25
1500uF/6.3V
C26
1500uF/6.3V
C28
1500uF/6.3V
C30
1500uF/6.3V
C32
1500uF/6.3V
PGND
May 18, 2005
1
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