LTC1629/LTC1629-PG
PolyPhase, High Efficiency,
Synchronous Step-Down Switching Regulators
FEATURES
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
s
s
s
s
s
s
Dual Controller Operates from One to Twelve Phases
Reduces Required Input Capacitance and Power
Supply Induced Noise
Current Mode Control Ensures Current Sharing
Phase-Lockable Fixed Frequency: 150kHz to 300kHz
1.8MHz Effective Switching Frequency
True Remote Sensing Differential Amplifier
OPTI-LOOP
TM
Compensation Reduces C
OUT
±
1% Output Voltage Accuracy
Power Good Output Voltage Monitor (LTC1629-PG)
Wide V
IN
Range: 4V to 36V Operation
Very Low Dropout Operation: 99% Duty Cycle
Adjustable Soft-Start Current Ramping
Internal Current Foldback Plus Shutdown Timer
Overvoltage Soft-Latch Eliminates Nuisance Trips
Micropower Shutdown
Available in 28-Lead SSOP Package
The LTC
®
1629/LTC1629-PG are multiple phase, dual,
synchronous step-down current mode switching regula-
tor controllers that drive N-channel external power MOSFET
stages in a phase-lockable fixed frequency architecture.
The PolyPhase
TM
controller drives its two output stages
out of phase at frequencies up to 300kHz to minimize the
RMS ripple currents in both input and output capacitors.
The output clock signal allows expansion for up to 12
evenly phased controllers for systems requiring 15A to
200A of output current. The multiple phase technique
effectively multiplies the fundamental frequency by the
number of channels used, improving transient response
while operating each channel at an optimum frequency for
efficiency. Thermal design is also simplified.
An internal differential amplifier provides true remote
sensing of the regulated supply’s positive and negative
output terminals as required for high current applications.
A RUN/SS pin provides both soft-start and optional timed,
short-circuit shutdown. Current foldback limits MOSFET
dissipation during short-circuit conditions when the
overcurrent latchoff is disabled. OPTI-LOOP compensa-
tion allows the transient response to be optimized over a
wide range of output capacitance and ESR values. The
LTC1629-PG includes a power good output pin that re-
places the AMPMD control pin of the LTC1629.
APPLICATIO S
s
s
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Desktop Computers
Internet Servers
Large Memory Arrays
DC Power Distribution Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
OPTI-LOOP and PolyPhase are trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
0.1µF
S
10Ω
10µF
×4
35V
CERAMIC
L1
1µH
D1
V
IN
LTC1629-PG TG1
BOOST1
SW1
M1
S
0.1µF
RUN/SS
1000pF
PGOOD
I
TH
3.3k
S
0.47µF
S
BG1
PGND
SENSE1
+
SENSE1
–
TG2
M3
S
M2
×2
SGND
16k
V
DIFFOUT
S
BOOST2
SW2
BG2
S
S
0.47µF
M4
×2
D2
L2
1µH
0.003Ω
+
EAIN
V
OS –
V
OS
+
INTV
CC
SENSE2
+
SENSE2
–
S
10µF
16k
C
OUT
: T510E108K004AS
D1, D2: UP5840
L1, L2: CEPH149-IROMC
M1, M3: IRF7811
M2, M4: IRF7809
Figure 1. High Current Dual Phase Step-Down Converter
U
V
IN
5V TO 28V
0.003Ω
V
OUT
1.6V/40A
U
U
+
C
OUT
1000µF
×2
4V
1629 TA01
1
LTC1629/LTC1629-PG
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
RUN/SS
SENSE1
+
SENSE1
–
EAIN
PLLFLTR
PLLIN
PHASMD
I
TH
SGND
1
2
3
4
5
6
7
8
9
28 CLKOUT
27 TG1
26 SW1
25 BOOST1
24 V
IN
23 BG1
22 EXTV
CC
21 INTV
CC
20 PGND
19 BG2
18 BOOST2
17 SW2
16 TG2
15 AMPMD*
Input Supply Voltage (V
IN
).........................36V to – 0.3V
Topside Driver Voltages (BOOST1,2) .........42V to – 0.3V
Switch Voltage (SW1, 2) .............................36V to – 5 V
SENSE1
+
, SENSE2
+
, SENSE1
–
,
SENSE2
–
Voltages ........................ (1.1)INTV
CC
to – 0.3V
EAIN, V
OS+
, V
OS–
, EXTV
CC
, INTV
CC
,
RUN/SS, AMPMD, PGOOD Voltages ............7V to – 0.3V
Boosted Driver Voltage (BOOST-SW) ..........7V to – 0.3V
PLLFLTR, PLLIN, CLKOUT, PHASMD,
V
DIFFOUT
Voltages ................................ INTV
CC
to – 0.3V
I
TH
Voltage ................................................2.7V to – 0.3V
Peak Output Current <1µs(TGL1,2, BG1,2) ................ 5A
INTV
CC
RMS Output Current ................................ 50mA
Operating Ambient Temperature Range
LTC1629C/LTC1629C-PG .......................... 0°C to 85°C
LTC1629I/LTC1629I-PG ....................... – 40°C to 85°C
Junction Temperature (Note 2) ............................. 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LTC1629CG
LTC1629IG
LTC1629CG-PG
LTC1629IG-PG
V
DIFFOUT
10
V
OS –
11
V
OS +
12
SENSE2
–
13
SENSE2
+
14
G PACKAGE
28-LEAD PLASTIC SSOP
*PGOOD ON LTC1629-PG
T
JMAX
= 125°C,
θ
JA
= 95°C/W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL
V
EAIN
V
SENSEMAX
I
INEAIN
V
LOADREG
PARAMETER
Regulated Feedback Voltage
Maximum Current Sense Threshold
Feedback Current
Output Voltage Load Regulation
Main Control Loop
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
RUN/SS
= 5V unless otherwise noted.
CONDITIONS
(Note 3); I
TH
Voltage = 1.2V
V
SENSE –
= 5V
V
SENSE1, 2
= 5V; LTC1629 Only
(Note 3)
(Note 3)
Measured in Servo Loop; I
TH
Voltage = 0.7V
Measured in Servo Loop; I
TH
Voltage = 2V
V
IN
= 3.6V to 30V (Note 3)
Measured at V
EAIN
V
IN
Ramping Down
I
TH
= 1.2V; Sink/Source 5µA; (Note 3)
I
TH
= 1.2V; (g
m
xZ
L
; No Ext Load); (Note 3)
(Note 4)
EXTV
CC
Tied to V
OUT
; V
OUT
= 5V
V
RUN/SS
= 0V
V
RUN/SS
= 1.9V
V
RUN/SS
Rising
V
RUN/SS
Rising from 3V
Soft Short Condition V
EAIN
= 0.5V; V
RUN/SS
= 4.5V
V
EAIN
= 0.5V
0.5
– 0.5
1.0
q
q
q
q
q
MIN
0.792
62
65
TYP
0.800
75
75
–5
0.1
– 0.1
0.002
MAX
0.808
88
85
– 50
0.5
– 0.5
0.02
0.88
4
UNITS
V
mV
mV
nA
%
%
%/V
V
V
mmho
V/mV
µA
µA
µA
V
V
µA
µA
V
REFLNREG
V
OVL
UVLO
g
m
g
mOL
I
Q
Reference Voltage Line Regulation
Output Overvoltage Threshold
Undervoltage Lockout
Transconductance Amplifier g
m
Transconductance Amplifier Gain
Input DC Supply Current
Normal Mode
Shutdown
Soft-Start Charge Current
RUN/SS Pin ON Threshold
RUN/SS Pin Latchoff Arming
RUN/SS Discharge Current
Shutdown Latch Disable Current
0.84
3
0.86
3.5
3
1.5
470
20
– 1.2
1.5
4.1
2
1.6
40
1.9
4.5
4
5
I
RUN/SS
V
RUN/SS
V
RUN/SSLO
I
SCL
I
SDLDO
2
U
W
U
U
W W
W
LTC1629/LTC1629-PG
ELECTRICAL CHARACTERISTICS
SYMBOL
I
SENSE
DF
MAX
TG1, 2 t
r
TG1, 2 t
f
BG1, 2 t
r
BG1, 2 t
f
TG/BG t
1D
BG/TG t
2D
t
ON(MIN)
V
INTVCC
V
LDO
INT
V
LDO
EXT
V
EXTVCC
V
LDOHYS
f
NOM
f
LOW
f
HIGH
R
PLLIN
I
PLLFLTR
PARAMETER
Total Sense Pins Source Current
Maximum Duty Factor
Top Gate Transition Time:
Rise Time
Fall Time
Bottom Gate Transition Time:
Rise Time
Fall Time
Top Gate Off to Bottom Gate On Delay
Synchronous Switch-On Delay Time
Bottom Gate Off to Top Gate On Delay
Top Switch-On Delay Time
Minimum On-Time
Internal V
CC
Voltage
INTV
CC
Load Regulation
EXTV
CC
Voltage Drop
EXTV
CC
Switchover Voltage
EXTV
CC
Switchover Hysteresis
Nominal Frequency
Lowest Frequency
Highest Frequency
PLLIN Input Resistance
Phase Detector Output Current
Sinking Capability
Sourcing Capability
Controller 2-Controller 1 Phase
Phase (Relative to Controller 1)
f
PLLIN
< f
OSC
f
PLLIN
> f
OSC
V
PHASMD
= 0V, Open
V
PHASMD
= 5V
V
PHASMD
= 0V
V
PHASMD
= Open
V
PHASMD
= 5V
4
0.2
I
PGOOD
= 2mA
V
PGOOD
= 5V
V
EAIN
with Respect to Set Output Voltage
V
EAIN
Ramping Negative
V
EAIN
Ramping Positive
Differential Amp Mode
Differential Amp Mode; 0V < V
CM
< 5V
Differential Amp Mode; Measured at V
OS
+ Input
–6
6
0.995
46
– 7.5
7.5
1
55
80
0.1
0.3
±1
– 9.5
9.5
1.005
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
RUN/SS
= 5V unless otherwise noted.
CONDITIONS
Each Channel; V
SENSE1
–
, 2
– = V
SENSE1
+
, 2
+ = 0V
In Dropout
C
LOAD
= 3300pF
C
LOAD
= 3300pF
C
LOAD
= 3300pF
C
LOAD
= 3300pF
C
LOAD
= 3300pF Each Driver
C
LOAD
= 3300pF Each Driver
Tested with a Square Wave (Note 6)
6V < V
IN
< 30V; V
EXTVCC
= 4V
I
CC
= 0 to 20mA; V
EXTVCC
= 4V
I
CC
= 20mA; V
EXTVCC
= 5V; LTC1629
I
CC
= 20mA; V
EXTVCC
= 5V; LTC1629-PG
I
CC
= 20mA, EXTV
CC
Ramping Positive
I
CC
= 20mA, EXTV
CC
Ramping Negative
V
PLLFLTR
= 1.2V
V
PLLFLTR
= 0V
V
PLLFLTR
≥
2.4V
190
120
280
q
MIN
– 85
98
TYP
– 60
99.5
30
40
30
20
90
90
180
MAX
UNITS
µA
%
90
90
90
90
ns
ns
ns
ns
ns
ns
ns
Internal V
CC
Regulator
4.8
5.0
0.2
120
80
4.5
4.7
0.2
220
140
310
50
– 15
15
180
240
60
90
120
250
160
360
5.2
1.0
240
160
V
%
mV
mV
V
V
kHz
kHz
kHz
kΩ
µA
µA
Deg
Deg
Deg
Deg
Deg
V
V
V
µA
%
%
V/V
dB
kΩ
Oscillator and Phase-Locked Loop
R
RELPHS
CLKOUT
CLK
HIGH
CLK
LOW
V
PGL
I
PGOOD
V
PG
Clock High Output Voltage
Clock Low Output Voltage
PGOOD Voltage Low
PGOOD Leakage Current
PGOOD Trip Level, Either Controller
PGOOD Output (LTC1629-PG Only)
Differential Amplifier/Op Amp Gain Block (Note 5)
A
DA
CMRR
DA
R
IN
Gain
Common Mode Rejection Ratio
Input Resistance
3
LTC1629/LTC1629-PG
ELECTRICAL CHARACTERISTICS
SYMBOL
V
OS
I
B
A
OL
V
CM
CMRR
OA
PSRR
OA
I
CL
V
OMAX
GBW
SR
PARAMETER
Input Offset Voltage
Input Bias Current
Open Loop DC Gain
Common Mode Input Voltage Range
Common Mode Rejection Ratio
Power Supply Rejection Ratio
Maximum Output Current
Maximum Output Voltage
Gain-Bandwidth Product
Slew Rate
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
RUN/SS1, 2
= 5V unless otherwise noted.
CONDITIONS
Op Amp Mode; V
CM
= 2.5V; LTC1629 Only
V
DIFFOUT
= 5V; I
DIFFOUT
= 1mA
Op Amp Mode; LTC1629 Only
Op Amp Mode; 0.7V
≤
V
DIFFOUT
< 10V; LTC1629 Only
Op Amp Mode; LTC1629 Only
Op Amp Mode; 0V < V
CM
< 3V; LTC1629 Only
Op Amp Mode; 6V < V
IN
< 30V; LTC1629 Only
Op Amp Mode; V
DIFFOUT
= 0V; LTC1629 Only
Op Amp Mode; I
DIFFOUT
= 1mA; LTC1629 Only
Op Amp Mode; I
DIFFOUT
= 1mA; LTC1629 Only
Op Amp Mode; R
L
= 2k; LTC1629 Only
0
70
70
10
10
90
90
35
11
2
5
30
5000
3
MIN
TYP
MAX
6
200
UNITS
mV
nA
V/mV
V
dB
dB
mA
V
MHz
V/µs
Note 1:
Absolute Maximum Ratings are those values beyond which the
life of a device may be impaired.
Note 2:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formulas:
LTC1629/LTC1629-PG: T
J
= T
A
+ (P
D
• 95°C/W)
Note 3:
The LTC1629/LTC1629-PG are tested in a feedback loop that
servos V
ITH
to a specified voltage and measures the resultant V
EAIN
.
Note 4:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 5:
When the AMPMD pin is high, the IC pins are connected directly to
the internal op amp inputs. When the AMPMD pin is low, internal MOSFET
switches connect four 40k resistors around the op amp to create a
standard unity-gain differential amp.
Note 6:
The minimum on-time condition corresponds to the on inductor
peak-to-peak ripple current
≥
40% of I
MAX
(see Minimum On-Time
Considerations in the Applications Information section).
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Output Current
(Figure 12)
100
100
V
EXTVCC
= 5V
80
V
IN
= 5V
EFFICIENCY (%)
EFFICIENCY (%)
60
V
IN
= 12V
V
IN
= 20V
80
40
70
EFFICIENCY (%)
V
IN
= 8V
20
V
OUT
= 3.3V
V
EXTVCC
= 5V
I
OUT
= 20A
0.1
1
10
OUTPUT CURRENT (A)
100
1629 G01
0
4
U W
Efficiency vs Output Current
(Figure 12)
100
Efficiency vs Input Voltage
(Figure 12)
V
OUT
= 3.3V
V
EXTVCC
= 5V
I
OUT
= 20A
90
90
V
EXTVCC
= 0V
80
60
V
OUT
= 3.3V
50
70
1
10
OUTPUT CURRENT (A)
100
1629 G02
5
10
V
IN
(V)
15
20
1629 G03
LTC1629/LTC1629-PG
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Input Voltage
and Mode
1000
250
INTV
CC
AND EXTV
CC
SWITCH VOLTAGE (V)
EXTV
CC
VOLTAGE DROP (mV)
800
SUPPLY CURRENT (µA)
600
ON
400
200
SHUTDOWN
0
0
5
20
15
10
25
INPUT VOLTAGE (V)
30
35
Internal 5V LDO Line Reg
5.1
5.0
I
LOAD
= 1mA
INTV
CC
VOLTAGE (V)
4.9
V
SENSE
(mV)
4.8
4.7
4.6
4.5
4.4
0
5
20
15
25
10
INPUT VOLTAGE (V)
30
35
1629 G07
V
SENSE
(mV)
Maximum Current Sense Threshold
vs V
RUN/SS
(Soft-Start)
80
V
SENSE(CM)
= 1.6V
80
60
V
SENSE
(mV)
V
SENSE
(mV)
72
V
SENSE
(mV)
40
20
64
0
0
1
2
3
V
RUN/SS
(V)
1629 G10
4
U W
1629 G04
EXTV
CC
Voltage Drop
5.05
5.00
4.95
4.90
4.85
4.80
4.75
INTV
CC
and EXTV
CC
Switch
Voltage vs Temperature
INTV
CC
VOLTAGE
200
LTC1629
150
LTC1629-PG
100
50
EXTV
CC
SWITCHOVER THRESHOLD
0
0
10
30
20
CURRENT (mA)
40
50
1629 G05
4.70
– 50 – 25
50
25
75
0
TEMPERATURE (°C)
100
125
1629 G06
Maximum Current Sense Threshold
vs Duty Factor
75
80
70
60
Maximum Current Sense Threshold
vs Percent of Nominal Output
Voltage (Foldback)
50
50
40
30
20
10
25
0
0
20
40
60
DUTY FACTOR (%)
80
100
1629 G08
0
50
100
0
25
75
PERCENT ON NOMINAL OUTPUT VOLTAGE (%)
1629 G09
Maximum Current Sense Threshold
vs Sense Common Mode Voltage
90
80
76
70
60
50
40
30
20
10
0
–10
–20
60
–30
Current Sense Threshold
vs I
TH
Voltage
68
5
6
0
1
3
4
2
COMMON MODE VOLTAGE (V)
5
1629 G11
0
0.5
1
1.5
V
ITH
(V)
2
2.5
1629 G12
5
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