LTC3714
Intel Compatible,
Wide Operating Range, Step-Down Controller
with Internal Op Amp
FeaTures
DescripTion
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True Current Mode with Ultrafast Transient Response
Stable with Ceramic C
OUT
t
ON(MIN)
< 100ns for Operation from High Input
Ranges
Supports Active Voltage Positioning
No Sense Resistor Required
5-Bit VID Programmable Output Voltage: 0.6V to 1.75V
Dual N-Channel MOSFET Synchronous Drive
Programmable Output Offsets
Power Good Output Voltage Monitor
Wide V
IN
Range: 4V to 36V
±1% 0.6V Reference
Adjustable Frequency
Programmable Soft-Start
Output Overvoltage Protection
Optional Short-Circuit Shutdown Timer
Forced Continuous Control Pin
Logic Controlled Micropower Shutdown: I
Q
≤ 30µA
Available in 0.209" Wide 28-Lead SSOP Package
The LTC
®
3714 is a synchronous step-down switching
regulator controller for CPU power. An output voltage
between 0.6V and 1.75V is selected by a 5-bit code (Intel
mobile VID specification). The controller uses a constant
on-time, valley current control architecture to deliver very
low duty cycles without requiring a sense resistor. Oper-
ating frequency is selected by an external resistor and is
compensated for variations in V
IN
and V
OUT
.
Discontinuous mode operation provides high efficiency
operation at light loads. A forced continuous control pin
reduces noise and RF interference and can assist second-
ary winding regulation by disabling discontinuous mode
when the main output is lightly loaded. Internal op amp
allows programmable offsets to the output voltage during
power saving modes.
Fault protection is provided by internal foldback current
limiting, an output overvoltage comparator and optional
short-circuit shutdown timer. Soft-start capability for
supply sequencing is accomplished using an external
timing capacitor. The regulator current limit level is user
programmable. Wide supply range allows operation from
4V to 36V at the input.
L,
LTC and LT are registered trademarks of Linear Technology Corporation.
Pentium is a registered trademark of Intel Corporation.
applicaTions
n
n
Power Supply for Mobile Pentium
®
Processors and
Transmeta Processors
Notebook and Portable Computers
Typical applicaTion
LTC3714
INTV
CC
C
SS
0.1µF
PGOOD
I
ON
V
IN
RUN/SS
R
C
I
TH
SGND
TG
SW
BOOST
INTV
CC
VID4
5-BIT
VID
VID3
VID2
VID1
VID0
PGND
V
OSENSE
*OPTIONAL
3714 F01
R
ON
V
IN
5V TO 24V
V
OUT
0.6V TO 1.75V
23A
Transient Response of 8A to 23A Output Load Step
M1
IRF7811 L1
×2
0.68µH
10µF
35V
×4
1.395V
V
OUT
1.35V
50mV/DIV
1.213V
23A
I
LOAD
10A/DIV
8A
20µs/DIV
3714 TA03
C
C
C
B
, 0.22µF
D
B
CMDSH-3
+
M2
IRF7811
×3
D1*
UPS840
C
OUT
270µF
2V
×4
BG
SENSE
+
C
VCC
4.7µF
0.003Ω*
Figure 1. High Efficiency Step-Down Converter
3714f
1
LTC3714
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
BG
PGND
SENSE
SW
TG
BOOST
VID0
VID1
VID2
1
2
3
4
5
6
7
8
9
28 INTV
CC
27 V
IN
26 EXTV
CC
25 VID4
24 VID3
23 V
OSENSE
22 VFB
21 I
ON
20 FCB
19 SGND
18 OPOUT
17 OP
+
16 OP
–
15 OPV
IN
Input Supply Voltage (V
IN
), I
ON
.................. 36V to –0.3V
Boosted Topside Driver Supply Voltage
(BOOST) ................................................... 42V to –0.3V
SW, SENSE Voltages .................................... 36V to –5V
EXTV
CC
, (BOOST – SW), RUN/SS, VID0-VID4,
PGOOD, FCB Voltages ................................ 7V to –0.3V
V
ON
, V
RNG
Voltages................. (INTV
CC
+ 0.3V) to –0.3V
I
TH
, V
FB
, V
OSENSE
Voltages....................... 2.7V to –0.3V
TG, BG, INTV
CC
, EXTV
CC
Peak Currents .................... 2A
TG, BG, INTV
CC
, EXTV
CC
RMS Currents ............... 50mA
OPV
IN
, OP
+
, OP
–
..............................................0V to 18V
Operating Ambient Temperature Range
LTC3714EG (Note 2) ............................ –40°C to 85°C
Junction Temperature (Note 3) ............................ 125°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
ORDER PART
NUMBER
LTC3714EG
RUN/SS 10
V
ON
11
PGOOD 12
V
RNG
13
I
TH
14
G PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 130°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
elecTrical characTerisTics
SYMBOL
I
Q
V
FB
∆V
FB(LINEREG)
∆V
FB(LOADREG)
g
m(EA)
V
FCB
I
FCB
t
ON
t
ON(MIN)
t
OFF(MIN)
V
SENSE(MAX)
V
SENSE(MIN)
∆V
FB(OV)
∆V
FB(UV)
V
RUN/SS(ON)
PARAMETER
Input DC Supply Current
Normal
Shutdown Supply Current
Feedback Reference Voltage
Feedback Voltage Line Regulation
Feedback Voltage Load Regulation
Error Amplifier Transconductance
Forced Continuous Threshold
Forced Continuous Current
On-Time
Minimum On-Time
Minimum Off-Time
Maximum Current Sense Threshold
Main Control Loop
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V unless otherwise noted.
CONDITIONS
MIN
TYP
MAX
UNITS
900
15
I
TH
= 1.2V (Note 4)
V
IN
= 4V to 30V (Note 4), I
TH
= 1.2V
I
TH
= 0.5V to 1.9V (Note 4)
I
TH
= 1.2V (Note 4)
V
FCB
= 0.6V
I
ON
= 60µA, V
ON
= 1.5V
I
ON
= 180µA, V
ON
= 0V
I
ON
= 60µA, V
ON
= 1.5V
V
RNG
= 1V, V
FB
= 0.56V
V
RNG
= 0V, V
FB
= 0.56V
V
RNG
= INTV
CC
, V
FB
= 0.56V
V
RNG
= 1V, V
FB
= 0.64V
V
RNG
= 0V, V
FB
= 0.64V
V
RNG
= INTV
CC
, V
FB
= 0.64V
7.5
340
l
l
l
l
l
l
l
l
2000
30
0.606
–0.3
2
0.63
–2
300
100
400
153
107
214
µA
µA
V
%/V
%
ms
V
µA
ns
ns
ns
mV
mV
mV
mV
mV
mV
0.594
0.600
0.002
–0.05
1.4
0.57
200
1.7
0.6
–1
250
50
250
113
79
158
133
93
186
–67
–33
–93
10
400
1.5
Minimum Current Sense Threshold
Output Overvoltage Fault Threshold
Output Undervoltage Fault Threshold
RUN Pin Start Threshold
12.5
460
2
%
mV
V
3714f
0.8
2
LTC3714
elecTrical characTerisTics
SYMBOL
V
RUN/SS(LE)
V
RUN/SS(LT)
I
RUN/SS(C)
I
RUN/SS(D)
V
IN(UVLO)
V
IN(UVLOR)
TG R
UP
TG R
DOWN
BG R
UP
BG R
DOWN
TG t
r
TG t
f
BG t
r
BG t
f
V
INTVCC
∆V
LDO(LOADREG)
V
EXTVCC
∆V
EXTVCC
∆V
EXTVCC(HYS)
PGOOD Output
∆V
FBH
∆V
FBL
∆V
FB(HYS)
V
PGL
VID DAC
V
VID(T)
I
VID(PULLUP)
V
VID(PULLUP)
I
VID(LEAK)
R
VID
∆V
OSENSE
VID0-VID4 Logic Threshold Voltage
VID0-VID4 Pull-Up Current
VID0-VID4 Pull-Up Voltage
VID0-VID4 Leakage Current
Resistance from V
OSENSE
to V
FB
DAC Output Accuracy
V
OSENSE
Programmed from
0.6V to 1.75V (Note 5)
V
VID0
to V
VID4
= 0V
V
VID0
to V
VID4
Open
V
VID0
to V
VID4
= 5V, V
RUN/SS
= 0V
6
–0.45
0.4
1.2
–2.5
4.5
0.01
10
0
1
14
0.25
2
V
µA
V
µA
kΩ
%
PGOOD Upper Threshold
PGOOD Lower Threshold
PGOOD Hysteresis
PGOOD Low Voltage
V
FB
Rising
V
FB
Falling
V
FB
Returning
I
PGOOD
= 1mA
7.5
–7.5
10
–10
1
0.15
12.5
–12.5
2.5
0.4
%
%
%
V
PARAMETER
RUN Pin Latchoff Enable Threshold
RUN Pin Latchoff Threshold
Soft-Start Charge Current
Soft-Start Discharge Current
Undervoltage Lockout Threshold
Undervoltage Lockout Threshold
TG Driver Pull-Up On Resistance
TG Driver Pull-Down On Resistance
BG Driver Pull-Up On Resistance
BG Driver Pull-Down On Resistance
TG Rise Time
TG Fall Time
BG Rise Time
BG Fall Time
Internal V
CC
Voltage
Internal V
CC
Load Regulation
EXTV
CC
Switchover Voltage
EXTV
CC
Switch Drop Voltage
EXTV
CC
Switchover Hysteresis
V
IN
Falling
V
IN
Rising
TG High
TG Low
BG High
BG Low
C
LOAD
= 3300pF
C
LOAD
= 3300pF
C
LOAD
= 3300pF
C
LOAD
= 3300pF
6V < V
IN
< 30V, V
EXTVCC
= 4V
I
CC
= 0mA to 20mA, V
EXTVCC
= 4V
I
CC
= 20mA, V
EXTVCC
Rising
I
CC
= 20mA, V
EXTVCC
= 5V
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V unless otherwise noted.
CONDITIONS
RUN/SS Pin Rising
RUN/SS Pin Falling
–0.5
0.8
MIN
TYP
4
3.5
–1.2
1.8
3.4
3.5
2
2
3
1
20
20
20
20
4.7
4.5
5
–0.1
4.7
150
200
300
5.3
±2
MAX
4.5
4.2
–3
3
3.9
4
3
3
4
2
UNITS
V
V
µA
µA
V
V
Ω
Ω
Ω
Ω
ns
ns
ns
ns
V
%
V
mV
mV
Internal V
CC
Regulator
V
IN
= 5V unless otherwise noted.
Internal Op Amp
V
OS
I
OS
I
B
CMRR
Input Offset Voltage
Input Offset Current
Input Bias Current
Common Mode Rejection Ratio
V
CM
= 0V to (V
CC
– 1V)
V
CM
= 0V to 18V
400
4
45
100
80
1000
10
80
µV
nA
nA
dB
dB
3714f
3
LTC3714
elecTrical characTerisTics
SYMBOL
PSRR
A
VOL
V
OL
V
OH
I
SC
I
S
PARAMETER
Power Supply Rejection Ratio
Large-Signal Voltage Gain
Output Voltage Swing LOW
Output Voltage Swing HIGH
Short-Circuit Current
Supply Current
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 5V unless otherwise noted.
CONDITIONS
OPV
IN
= 3V to 12.5V, OP
OUT
= V
O
= 1V
OPV
IN
= 5V, OP
OUT
= 500mV to 4.5V, R
L
= 10k
OPV
IN
= 5V, I
SINK
= 5mA
OPV
IN
= 5V, I
SOURCE
= 5mA
Short to GND
Short to OPV
IN
l
l
MIN
TYP
100
1500
165
MAX
UNITS
dB
V/mV
500
mV
V
mA
mA
4.5
4.87
30
40
170
300
µA
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
The LTC3714E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
as follows:
LTC3714EG: T
J
= T
A
+ (P
D
• 130°C/W)
Note 4:
The LTC3714 is tested in a feedback loop that adjusts V
FB
to
achieve a specified error amplifier output voltage (I
TH
).
Note 5:
The LTC3714 VID DAC is tested in a feedback loop that adjusts
V
OSENSE
to achieve a specified feedback voltage (V
FB
= 0.6V) for each DAC
VID code.
3714f
4
LTC3714
Typical perForMance characTerisTics
Transient Response
V
OUT
50mV/DIV
Transient Response
(Discontinuous Mode)
RUN/SS
2V/DIV
V
OUT
500mV/DIV
Start-Up
V
OUT
50mV/DIV
I
L
5A/DIV
I
L
5A/DIV
I
L
5A/DIV
20µs/DIV
LOAD STEP 0A TO 10A
V
IN
= 15V
V
OUT
= 1.5V
FCB = 0V
FIGURE 1 CIRCUIT
3714 G01
20µs/DIV
LOAD STEP 0A TO 10A
V
IN
= 15V
V
OUT
= 1.5V
FCB = INTV
CC
FIGURE 1 CIRCUIT
3714 G02
50ms/DIV
V
IN
= 15V
V
OUT
= 1.25V
R
LOAD
= 0.125Ω
3714 G03
Efficiency vs Load Current
95
V
IN
= 8.5V
V
IN
= 15V
EFFICIENCY (%)
100
Efficiency vs Input Voltage
300
280
FREQUENCY (kHz)
I
OUT
= 10A
Frequency vs Input Voltage
FCB = 0V
FIGURE 1 CIRCUIT
I
OUT
= 10A
90
EFFICIENCY (%)
90
85
260
240
I
OUT
= 0A
80
80
V
IN
= 24V
I
OUT
= 1A
I
OUT
= 23A
75
70
V
OUT
= 1.35V
FREQUENCY = 300kHz
FIGURE 1 CIRCUIT
0
3
6
9
12 15 18
LOAD CURRENT (A)
21
3714 G04
70
220
60
0
5
10
15
20
INPUT VOLTAGE (V)
25
30
3714 G05
200
5
10
15
INPUT VOLTAGE (V)
20
25
3714 G06
Load Regulation
0
NO AVP
FIGURE 1 CIRCUIT
2.5
2.0
I
TH
VOLTAGE (V)
I
TH
Voltage vs Load Current
FIGURE 1 CIRCUIT
CURRENT SENSE THRESHOLD (mV)
300
Current Sense Threshold
vs I
TH
Voltage
V
RNG
=
2V
1.4V
1V
0.7V
0.5V
–0.1
∆V
OUT
(%)
200
1.5
1.0
CONTINUOUS
MODE
100
–0.2
0
–0.3
0.5
DISCONTINUOUS
MODE
–100
–200
–0.4
0
2
6
4
LOAD CURRENT (A)
8
10
3714 G07
0
0
10
5
LOAD CURRENT (A)
15
3714 G08
0
0.5
1.0
1.5
2.0
I
TH
VOLTAGE (V)
2.5
3.0
3714 G09
3714f
5
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