1
LTC3713
3713fa
FEATURES
APPLICATIO S
U
DESCRIPTIO
U
TYPICAL APPLICATIO
U
Low Input Voltage,
High Power, No R
SENSE
TM
Synchronous Buck DC/DC Controller
s
Very Low V
IN(MIN)
: 1.5V
s
True Current Mode Control
s
5V Drive for N-Channel MOSFETs Eliminates
Auxillary 5V Supply
s
No Sense Resistor
Required
s
Uses Standard 5V Logic-Level N-Channel MOSFETs
s
Adjustable Current Limit
s
Adjustable Frequency
s
Switch t
ON(MIN)
< 100ns
s
2% to 90% Duty Cycle at 200kHz
s
0.8V
1% Reference
s
Power Good Output Voltage Monitor
s
Programmable Soft-Start
s
Output Overvoltage Protection
s
Optional Short-Circuit Shutdown Timer
s
Small 24-Lead SSOP Package
s
Telecom Card 3.3V, 2.5V, 1.8V Step-Down
s
Bus Termination (DDR memory, SSTL)
s
Synchronous Buck with General Purpose Boost
s
Low V
IN
Synchronous Boost
The LTC
3713 is a high current, high efficiency synchro-
nous buck switching regulator controller optimized for
use with very low input supply voltages. It operates from
inputs as low as 1.5V and provides a regulated output
voltage from 0.8V up to (0.9)V
IN
. The controller uses
a valley current control architecture to enable high operat-
ing frequencies without requiring a sense resistor.
Operating frequency is selected by an external resistor and
is compensated for variations in V
IN
and V
OUT
. The LTC3713
uses a pair of standard 5V logic-level N-channel external
MOSFETs, eliminating the need for expensive P-channel
or low threshold devices.
Discontinuous mode operation provides high efficiency
operation at light loads. A forced continuous control
pin reduces noise and RF interference, and can assist
secondary winding regulation by disabling discontinuous
operation when the main output is lightly loaded. Fault
protection is provided by internal foldback current limit-
ing, an output overvoltage comparator and an optional
short-circuit shutdown timer.
Figure 1. High Efficiency Step-Down Converter from 1.8V to 3.3V Input
Efficiency vs Load Current
, LTC and LT are registered trademarks of Linear Technology Corporation.
RUN/SS
BOOST
TG
SW1
SENSE
+
SENSE
0.33
F
LTC3713
5.6k
10k
20k
680pF
0.1
F
M1
CMDSH-3
PGND
BG
INTV
CC
V
IN1
V
IN2
I
TH
PGOOD
I
ON
V
FB1
SHDN
SGND
V
FB2
SW2
10
F
M2
B340A
C
OUT
: PANASONIC EEFUEOD271R
L1: (A) PANASONIC ETQP6FIR8BFA
(B) TOKO D104C-1.8
H
M1, M2: (A) IRF7822, (B) IRF7811A
L1
1.8
H
C
OUT
270
F
2
3713 F01a
22
F
2
V
IN
1.8V TO 3.3V
V
OUT
1.25V
10A
4.7
F
4.7
H
MBR0520
12.1k
37.4k
330k
+
No R
SENSE
is a trademark of Linear Technology Corporation.
LOAD CURRENT (A)
0.01
0
EFFICIENCY (%)
10
30
40
50
100
70
0.10
1
3
3713 F01b
20
80
A
B
90
60
0.04
0.40
7
12
15
V
IN
= 2.5V
2
LTC3713
3713fa
(Note 1)
Input Supply Voltage (V
IN2
) ....................... 10V to 0.3V
Boosted Topside Driver Supply Voltage
(BOOST) ............................................... 42V to 0.3V
V
IN1
, I
ON
, SW1, SENSE
+
Voltages ............. 36V to 0.3V
RUN/SS, PGOOD Voltages ......................... 7V to 0.3V
FCB, V
ON
, V
RNG
Voltages .......... INTV
CC
+ 0.3V to 0.3V
I
TH
, V
FB1
, SENSE
Voltages ..................... 2.7V to 0.3V
SW2 Voltage ............................................. 36V to 0.4V
V
FB2
Voltage ................................................. V
IN2
+ 0.3V
SHDN Voltage ......................................................... 10V
TG, BG, INTV
CC
Peak Currents .................................. 2A
TG, BG, INTV
CC
RMS Currents ............................ 50mA
Operating Ambient Temperature
Range (Note 4) ................................... 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
LTC3713EG
T
JMAX
= 125
C,
JA
= 130
C/ W
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are T
A
= 25
C. V
IN1
= 15V, V
IN2
= 1.5V unless otherwise noted.
ABSOLUTE AXI U RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
ELECTRICAL CHARACTERISTICS
1
2
3
4
5
6
7
8
9
10
11
12
TOP VIEW
G PACKAGE
24-LEAD PLASTIC SSOP
24
23
22
21
20
19
18
17
16
15
14
13
RUN/SS
V
ON
PGOOD
V
RNG
FCB
I
TH
SGND1
I
ON
V
FB1
SHDN
SGND2
V
FB2
BOOST
TG
SW1
SENSE
+
SENSE
PGND1
BG
INTV
CC
V
IN1
V
IN2
PGND2
SW2
Consult LTC Marketing for parts specified with wider operating temperature ranges.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Buck Regulator
I
Q(VIN1)
Input DC Supply Current (V
IN1
)
Normal
900
2000
A
Shutdown Supply Current
15
30
A
V
FB1
Feedback Reference Voltage
I
TH
= 1.2V (Note 3)
q
0.792
0.800
0.808
V
I
FB1
Feedback Current
(Note 3)
5
50
nA
V
FB1(LINEREG)
Feedback Voltage Line Regulation
V
IN1
= 4V to 30V, I
TH
= 1.2V (Note 3)
0.002
%/V
V
FB1(LOADREG)
Feedback Voltage Load Regulation
I
TH
= 0.5V to 1.9V (Note 3)
q
0.05
0.3
%
g
m(EA)
Error Amplifier Transconductance
I
TH
= 1.2V (Note 3)
q
1.4
1.7
2
mS
V
FCB
Forced Continuous Threshold
q
0.76
0.8
0.84
V
I
FCB
Forced Continuous Pin Current
V
FCB
= 0.8V
1
2
A
t
ON
On-Time
I
ON
= 60
A, V
ON
= 1.5V
200
250
300
ns
I
ON
= 30
A, V
ON
= 1.5V
400
500
600
ns
t
ON(MIN)
Minimum On-Time
I
ON
= 180
A
50
100
ns
t
OFF(MIN)
Minimum Off-Time
250
400
ns
V
SENSE(MAX)
Maximum Current Sense Threshold
V
RNG
= 1V, V
FB1
= 0.76V
q
113
133
153
mV
V
PGND
V
SW
V
RNG
= 0V, V
FB1
= 0.76V
q
79
93
107
mV
V
RNG
= INTV
CC
, V
FB1
= 0.76V
q
158
186
214
mV
V
SENSE(MIN)
Minimum Current Sense Threshold
V
RNG
= 1V, V
FB1
= 0.84V
67
mV
V
PGND
V
SW
V
RNG
= 0V, V
FB1
= 0.84V
47
mV
V
RNG
= INTV
CC
, V
FB1
= 0.84V
93
mV
V
FB1(OV)
Output Overvoltage Fault Threshold
5.5
7.5
9.5
%
V
FB1(UV)
Output Undervoltage Fault Threshold
520
600
680
mV
V
RUN/SS(ON)
RUN Pin Start Threshold
q
0.8
1.5
2
V
V
RUN/SS(LE)
RUN Pin Latchoff Enable Threshold
RUN/SS Pin Rising
4
4.5
V
V
RUN/SS(LT)
RUN Pin Latchoff Threshold
RUN/SS Pin Falling
3.5
4.2
V
3
LTC3713
3713fa
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are T
A
= 25
C. V
IN1
= 15V, V
IN2
= 1.5V unless otherwise noted.
ELECTRICAL CHARACTERISTICS
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
as follows:
LTC3713EG: T
J
= T
A
+ (P
D
130
C/W)
Note 3: The LTC3713 is tested in a feedback loop that adjusts V
FB
to
achieve a specified error amplifier output voltage (I
TH
).
Note 4: The LTC3713E 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 5: Current limit guaranteed by design and/or correlation to static test.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
RUN/SS(C)
Soft-Start Charge Current
V
RUN/SS
= 0V
0.5
1.2
3
A
I
RUN/SS(D)
Soft-Start Discharge Current
V
RUN/SS
= 4.5V, V
FB
= 0V
0.8
1.8
3
A
UVLO
V
IN1
Undervoltage Lockout
V
IN1
Falling
q
3.4
3.9
V
UVLOR
V
IN1
Undervoltage Lockout Release
V
IN1
Rising
q
3.5
4
V
TG R
UP
TG Driver Pull-Up On Resistance
TG High
2
3
TG R
DOWN
TG Driver Pull-Down On Resistance
TG Low
2
3
BG R
UP
BG Driver Pull-Up On Resistance
BG High
3
4
BG R
DOWN
BG Driver Pull-Down On Resistance
BG Low
1
2
TG t
r
TG Rise Time
C
LOAD
= 3300pF
20
ns
TG t
f
TG Fall Time
C
LOAD
= 3300pF
20
ns
BG t
r
BG Rise Time
C
LOAD
= 3300pF
20
ns
BG t
f
BG Fall Time
C
LOAD
= 3300pF
20
ns
Internal V
CC
Regulator
V
INTVCC
Internal V
CC
Voltage
6V < V
IN
< 30V
q
4.7
5
5.3
V
V
LDO(LOADREG)
Internal V
CC
Load Regulation
I
CC
= 0mA to 20mA
0.1
2
%
PGOOD Output
V
FB1H
PGOOD Upper Threshold
V
FB1
Rising
5.5
7.5
9.5
%
V
FB1L
PGOOD Lower Threshold
V
FB1
Falling
5.5
7.5
9.5
%
V
FB(HYS)
PGOOD Hysteresis
V
FB1
Returning
1
2
%
V
PGL
PGOOD Low Voltage
I
PGOOD
= 5mA
0.15
0.4
V
Boost Regulator
V
IN2(MIN)
Minimum Operating Voltage
0.9
1.5
V
V
IN2(MAX)
Maximum Operating Voltage
10
V
I
Q(VIN2)
Input DC Supply Current (V
IN2
)
Normal
3
4.5
mA
Shutdown
0.01
1
A
V
FB2
V
FB2
Feedback Voltage
0
C to 70
C
1.205
1.23
1.255
V
40
C to 85
C
q
1.200
1.260
V
I
VFB2
V
FB2
Pin Bias Current
q
27
80
nA
V
FB2(LINEREG)
BOOST Reference Line Regulation
1.5V
V
IN
10V
0.02
0.2
%/V
f
BOOST
BOOST Switching Frequency
0
C to 70
C
1.0
1.4
1.8
MHz
40
C to 85
C
q
0.9
1.9
MHz
DC
BOOST(MAX)
BOOST Maximum Duty Cycle
82
86
%
I
LIM(BOOST)
BOOST Switch Current Limit
(Note 5)
500
800
mA
V
CESAT(BOOST)
BOOST Switch V
CESAT
I
SW
= 300mA
300
350
mV
I
SWLKG(BOOST)
BOOST Switch Leakage Current
V
SW
= 5V
0.01
1
A
V
SHDN(HIGH)
SHDN Input Voltage High
1
V
V
SHDN(LOW)
SHDN Input Voltage Low
0.3
V
I
SHDN
SHDN Pin Bias Current
V
SHDN
= 3V
25
50
A
V
SHDN
= 0V
0.01
0.1
A
4
LTC3713
3713fa
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Transient Response
(Discontinuous Mode)
Transient Response
Boost Converter Oscillator
Frequency vs Temperature
Boost Converter Current Limit
vs Duty Cycle
SHDN Pin Current vs V
SHDN
V
FB2
, Feedback Pin Voltage
V
OUT
100mV/DIV
I
L
5A/DIV
50
s/DIV
3713 G01
LOAD STEP 0A TO 6A
V
IN
= 3.3V
V
OUT
= 1.25V
FCB = 0V
FIGURE 1 CIRCUIT
V
OUT
100mV/DIV
I
L
5A/DIV
50
s/DIV
3713 G02
LOAD STEP 600mA TO 6A
V
IN
= 3.3V
V
OUT
= 1.25V
FCB = INTV
CC
FIGURE 1 CIRCUIT
V
OUT
500mV/DIV
I
L
5A/DIV
500
s/DIV
3713 G03
V
IN
= 3.3V
V
OUT
= 1.25V
L = 1.8
H
C
OUT
= 540
F
LOAD = 0.2
Start-Up from Shutdown
TEMPERATURE (
C)
50
25
0
25
50
75
100
SWITCHING FREQUENCY (MHz)
3713 G04
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
V
IN
= 5V
V
IN
= 1.5V
SHDN PIN VOLTAGE (V)
0
1
2
3
4
5
SHDN PIN BIAS CURRENT (
A)
3713 G05
50
40
30
20
10
0
T
A
= 25
C
DUTY CYCLE (%)
10
20
30
40
50
60
70
80
CURRENT LIMIT (mA)
3713 G06
1000
900
800
700
600
500
400
300
200
70
C
25
C
40
C
TEMPERATURE (
C)
50
FEEDBACK PIN VOLTAGE (V)
3713 G07
1.25
1.24
1.23
1.22
1.21
1.20
VOLTAGE
25
0
25
50
75
100
Efficiency vs Load Current
(Discontinuous Mode)
LOAD CURRENT (A)
0.01
70
80
100
0.4
4
1
1713 G09
60
50
0.04 0.07 0.1
0.7
7
10
40
30
90
EFFICIENCY (%)
V
IN
= 2.5V
V
IN
= 3.3V
FIGURE 1 CIRCUIT (B)
LOAD CURRENT (A)
0.01
0
EFFICIENCY (%)
10
30
40
50
100
70
0.09
0.8
3
3713 G10
20
80
90
60
0.05
0.4
7
V
IN
= 3.3V
V
IN
= 2.5V
FIGURE 1 CIRCUIT (B)
Efficiency vs Load Current
(Force Continuous)
5
LTC3713
3713fa
Frequency vs Input Voltage
Load Regulation
On-Time vs I
ON
Current
On-Time vs V
ON
Voltage
On-Time vs Temperature
Current Limit Foldback
Maximum Current Sense
Threshold vs V
RNG
Voltage
Maximum Current Sense
Threshold vs RUN/SS Voltage
Maximum Current Sense
Threshold vs Temperature
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
LOAD CURRENT (A)
0
V
OUT
(%)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
3713 G11
2
10
5
1
3
8
9
7
6
4
FIGURE 1 CIRCUIT
INPUT VOLTAGE (V)
1.5
350
300
250
200
150
100
50
0
3.0
4.0
3713 G12
2.0
2.5
3.5
4.5
5.0
FREQUENCY (kHz)
FIGURE 1 CIRCUIT
LOAD = 0A
LOAD = 6A
I
ON
CURRENT (
A)
1
10
ON-TIME (ns)
100
1k
10k
10
100
3713 G13
V
VON
= 0V
V
ON
VOLTAGE (V)
0
ON-TIME (ns) 400
600
3713 G14
200
0
1
2
3
1000
I
ION
= 30
A
800
TEMPERATURE (
C)
50
ON-TIME (ns)
200
250
300
25
75
3713 G15
150
100
25
0
50
100
125
50
0
I
ION
= 30
A
V
FB
(V)
0
0
MAXIMUM CURRENT SENSE THRESHOLD (mV)
25
50
75
100
125
150
V
RNG
= 1V
0.2
0.4
0.6
0.8
3713 G16
V
RNG
VOLTAGE (V)
0.5
0
MAXIMUM CURRENT SENSE THRESHOLD (mV)
50
100
150
200
300
0.75
1.0
1.25
1.5
3713 G17
1.75
2.0
250
RUN/SS VOLTAGE (V)
1.5
0
MAXIMUM CURRENT SENSE THRESHOLD (mV)
25
50
75
100
125
150
V
RNG
= 1V
2
2.5
3
3.5
3713 G18
TEMPERATURE (
C)
50
25
100
MAXIMUM CURRENT SENSE THRESHOLD (mV)
120
150
0
50
75
3713 G19
110
140
130
25
100
125
V
RNG
= 1V
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