LTC3714
Intel Compatible,
Wide Operating Range, Step-Down Controller
with Internal Op Amp
DESCRIPTIO
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 sup-
ply sequencing is accomplished using an external timing
capacitor. The regulator current limit level is user pro-
grammable. Wide supply range allows operation from 4V
to 36V at the input.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Pentium is a registered trademark of Intel Corporation.
FEATURES
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
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
APPLICATIO S
s
s
Power Supply for Mobile Pentium
®
Processors and
Transmeta Processors
Notebook and Portable Computers
TYPICAL APPLICATIO
LTC3714
INTV
CC
C
SS
0.1µF
PGOOD
I
ON
V
IN
RUN/SS
I
TH
C
C
R
C
SGND
INTV
CC
VID4
VID3
5-BIT
VID
VID2
VID1
VID0
PGND
V
OSENSE
*OPTIONAL
BG
SENSE
TG
SW
BOOST
C
B
, 0.22µF
D
B
CMDSH-3
R
ON
Transient Response of 8A to 23A Output Load Step
M1
IRF7811 L1
×2
0.68µH
10µF
35V
×4
V
IN
5V TO 24V
+
M2
IRF7811
×3
D1*
UPS840
C
OUT
270µF
2V
×4
V
OUT
0.6V TO 1.75V
23A
+
C
VCC
4.7µF
0.003Ω*
3714 F01
Figure 1. High Efficiency Step-Down Converter
U
U
U
1.395V
V
OUT
(1.35V)
50mV/DIV
1.213V
23A
I
LOAD
10A/DIV
8A
20µs/DIV
3714 TA03
3714f
1
LTC3714
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
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
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
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are 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
q
q
q
q
q
q
q
q
2000
30
0.606
– 0.3
2
0.63
–2
300
100
400
153
107
214
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)
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
V
SENSE(MIN)
Minimum Current Sense Threshold
∆V
FB(OV)
∆V
FB(UV)
V
RUN/SS(ON)
Output Overvoltage Fault Threshold
Output Undervoltage Fault Threshold
RUN Pin Start Threshold
12.5
460
2
0.8
2
U
µA
µA
V
%/V
%
ms
V
µA
ns
ns
ns
mV
mV
mV
mV
mV
mV
%
mV
V
3714f
W
U
U
W W
W
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
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
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are T
A
= 25°C. V
IN
= 15V unless otherwise noted.
CONDITIONS
RUN/SS Pin Rising
RUN/SS Pin Falling
– 0.5
0.8
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
q
q
q
q
MIN
TYP
4
3.5
–1.2
1.8
3.4
3.5
2
2
3
1
20
20
20
20
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
Internal V
CC
Regulator
4.7
4.5
5
– 0.1
4.7
150
200
V
FB
Rising
V
FB
Falling
V
FB
Returning
I
PGOOD
= 1mA
0.4
V
VID0
to V
VID4
= 0V
V
VID0
to V
VID4
Open
V
VID0
to V
VID4
= 5V, V
RUN/SS
= 0V
6
V
OSENSE
Programmed from
0.6V to 1.75V (Note 5)
– 0.45
7.5
– 7.5
10
–10
1
0.15
1.2
– 2.5
4.5
0.01
10
0
1
14
0.25
12.5
–12.5
2.5
0.4
2
300
5.3
±2
V
%
V
mV
mV
%
%
%
V
V
µA
V
µA
KΩ
%
∆V
LDO(LOADREG)
Internal V
CC
Load Regulation
V
EXTVCC
EXTV
CC
Switchover Voltage
∆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
PGOOD Upper Threshold
PGOOD Lower Threshold
PGOOD Hysteresis
PGOOD Low Voltage
EXTV
CC
Switch Drop Voltage
EXTV
CC
Switchover Hysteresis
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
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are T
A
= 25°C. V
IN
= 5V unless otherwise noted.
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
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
q
q
ELECTRICAL CHARACTERISTICS
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 PERFOR A CE CHARACTERISTICS
Transient Response
Transient Response
(Discontinuous Mode)
RUN/SS
2V/DIV
V
OUT
500mV/DIV
I
L
5A/DIV
I
L
5A/DIV
I
L
5A/DIV
V
OUT
50mV/DIV
20µs/DIV
LOAD STEP 0A TO 10A
V
IN
= 15V
V
OUT
= 1.5V
FCB = 0V
FIGURE 1 CIRCUIT
Efficiency vs Load Current
95
100
90
EFFICIENCY (%)
V
IN
= 8.5V
V
IN
= 15V
EFFICIENCY (%)
FREQUENCY (kHz)
85
80
V
IN
= 24V
75
V
OUT
= 1.35V
FREQUENCY = 300kHz
FIGURE 1 CIRCUIT
60
70
0
3
6
9
12 15 18
LOAD CURRENT (A)
Load Regulation
0
NO AVP
FIGURE 1 CIRCUIT
2.5
–0.1
2.0
CURRENT SENSE THRESHOLD (mV)
I
TH
VOLTAGE (V)
∆V
OUT
(%)
–0.2
–0.3
0.5
–0.4
0
2
6
4
LOAD CURRENT (A)
U W
21
3714 G03
Start-Up
V
OUT
50mV/DIV
3714 G01
20µs/DIV
LOAD STEP 1A 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 G19
Efficiency vs Input Voltage
300
Frequency vs Input Voltage
FCB = 0V
FIGURE 1 CIRCUIT
I
OUT
= 10A
280
90
I
OUT
= 10A
260
80
I
OUT
= 1A
I
OUT
= 23A
240
I
OUT
= 0A
70
220
0
5
10
15
20
INPUT VOLTAGE (V)
25
30
3714 G04
200
5
10
15
INPUT VOLTAGE (V)
20
25
3714 G05
I
TH
Voltage vs Load Current
300
FIGURE 1 CIRCUIT
Current Sense Threshold
vs I
TH
Voltage
V
RNG
=
2V
1.4V
1V
100
0.7V
0.5V
200
1.5
CONTINUOUS
MODE
1.0
DISCONTINUOUS
MODE
0
–100
8
10
3714 G06
0
–200
0
10
5
LOAD CURRENT (A)
15
3714 G07
0
0.5
1.0
1.5
2.0
I
TH
VOLTAGE (V)
2.5
3.0
3714 G08
3714f
5
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