LTC3713
Low Input Voltage,
High Power, No R
SENSE
TM
Synchronous Buck DC/DC Controller
FEATURES
s
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
s
s
s
s
Very Low V
IN(MIN)
: 1.5V
True Current Mode Control
5V Drive for N-Channel MOSFETs Eliminates
Auxillary 5V Supply
No Sense Resistor Required
Uses Standard 5V Logic-Level N-Channel MOSFETs
Adjustable Current Limit
Adjustable Frequency
Switch t
ON(MIN)
< 100ns
2% to 90% Duty Cycle at 200kHz
0.8V
±1%
Reference
Power Good Output Voltage Monitor
Programmable Soft-Start
Output Overvoltage Protection
Optional Short-Circuit Shutdown Timer
Small 24-Lead SSOP Package
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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
No R
SENSE
is a trademark of Linear Technology Corporation.
APPLICATIO S
s
s
s
s
Telecom Card 3.3V, 2.5V, 1.8V Step-Down
Bus Termination (DDR memory, SSTL)
Synchronous Buck with General Purpose Boost
Low V
IN
Synchronous Boost
TYPICAL APPLICATIO
SHDN
330k
5.6k
I
ON
TG
LTC3713
SW1
V
FB1
10k
SENSE
+
680pF
20k
I
TH
BG
PGND
–
CMDSH-3
BOOST
0.33µF
M1
L1
1.8µH
V
IN
1.8V TO 3.3V
22µF
×2
100
+
M2
B340A
EFFICIENCY (%)
C
OUT
270µF
×2
V
OUT
1.25V
10A
SENSE
RUN/SS INTV
CC
0.1µF
PGOOD
SGND
V
IN1
V
IN2
10µF
3713 F01a
4.7µF
MBR0520
4.7µH
12.1k
V
FB2
SW2
37.4k
C
OUT
: PANASONIC EEFUEOD271R
L1: (A) PANASONIC ETQP6FIR8BFA
(B) TOKO D104C-1.8µH
M1, M2: (A) IRF7822, (B) IRF7811A
Figure 1. High Efficiency Step-Down Converter from 1.8V to 3.3V Input
3713fa
U
Efficiency vs Load Current
90
80
70
60
50
40
30
20
10
0
0.01 0.04 0.10 0.40 1
7
3
LOAD CURRENT (A)
12
15
V
IN
= 2.5V
A
B
3713 F01b
U
U
1
LTC3713
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
RUN/SS
V
ON
PGOOD
V
RNG
FCB
I
TH
SGND1
I
ON
V
FB1
1
2
3
4
5
6
7
8
9
24 BOOST
23 TG
22 SW1
21 SENSE
+
20 SENSE
–
19 PGND1
18 BG
17 INTV
CC
16 V
IN1
15 V
IN2
14 PGND2
13 SW2
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
SHDN 10
SGND2 11
V
FB2
12
G PACKAGE
24-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
PARAMETER
Buck Regulator
I
Q(VIN1)
Input DC Supply Current (V
IN1
)
Normal
Shutdown Supply Current
V
FB1
Feedback Reference Voltage
I
FB1
Feedback Current
∆V
FB1(LINEREG)
Feedback Voltage Line Regulation
∆V
FB1(LOADREG)
Feedback Voltage Load Regulation
g
m(EA)
Error Amplifier Transconductance
V
FCB
Forced Continuous Threshold
I
FCB
Forced Continuous Pin Current
t
ON
On-Time
t
ON(MIN)
t
OFF(MIN)
V
SENSE(MAX)
V
SENSE(MIN)
∆V
FB1(OV)
∆V
FB1(UV)
V
RUN/SS(ON)
V
RUN/SS(LE)
V
RUN/SS(LT)
Minimum On-Time
Minimum Off-Time
Maximum Current Sense Threshold
V
PGND
– V
SW
Minimum Current Sense Threshold
V
PGND
– V
SW
Output Overvoltage Fault Threshold
Output Undervoltage Fault Threshold
RUN Pin Start Threshold
RUN Pin Latchoff Enable Threshold
RUN Pin Latchoff Threshold
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.
CONDITIONS
MIN
TYP
MAX
UNITS
I
TH
= 1.2V (Note 3)
(Note 3)
V
IN1
= 4V to 30V, I
TH
= 1.2V (Note 3)
I
TH
= 0.5V to 1.9V (Note 3)
I
TH
= 1.2V (Note 3)
V
FCB
= 0.8V
I
ON
= 60µA, V
ON
= 1.5V
I
ON
= 30µA, V
ON
= 1.5V
I
ON
= 180µA
V
RNG
= 1V, V
FB1
= 0.76V
V
RNG
= 0V, V
FB1
= 0.76V
V
RNG
= INTV
CC
, V
FB1
= 0.76V
V
RNG
= 1V, V
FB1
= 0.84V
V
RNG
= 0V, V
FB1
= 0.84V
V
RNG
= INTV
CC
, V
FB1
= 0.84V
q
0.792
q
q
q
1.4
0.76
200
400
q
q
q
113
79
158
q
5.5
520
0.8
RUN/SS Pin Rising
RUN/SS Pin Falling
900
15
0.800
–5
0.002
– 0.05
1.7
0.8
–1
250
500
50
250
133
93
186
– 67
– 47
– 93
7.5
600
1.5
4
3.5
2000
30
0.808
±50
– 0.3
2
0.84
–2
300
600
100
400
153
107
214
9.5
680
2
4.5
4.2
2
U
µA
µA
V
nA
%/V
%
mS
V
µA
ns
ns
ns
ns
mV
mV
mV
mV
mV
mV
%
mV
V
V
V
3713fa
W
U
U
W W
W
LTC3713
ELECTRICAL CHARACTERISTICS
SYMBOL
I
RUN/SS(C)
I
RUN/SS(D)
UVLO
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)
PGOOD Output
∆V
FB1H
∆V
FB1L
∆V
FB(HYS)
V
PGL
Boost Regulator
V
IN2(MIN)
V
IN2(MAX)
I
Q(VIN2)
Minimum Operating Voltage
Maximum Operating Voltage
Input DC Supply Current (V
IN2
)
Normal
Shutdown
V
FB2
Feedback Voltage
V
FB2
Pin Bias Current
BOOST Reference Line Regulation
BOOST Switching Frequency
BOOST Maximum Duty Cycle
BOOST Switch Current Limit
BOOST Switch V
CESAT
BOOST Switch Leakage Current
SHDN Input Voltage High
SHDN Input Voltage Low
SHDN Pin Bias Current
PGOOD Upper Threshold
PGOOD Lower Threshold
PGOOD Hysteresis
PGOOD Low Voltage
PARAMETER
Soft-Start Charge Current
Soft-Start Discharge Current
V
IN1
Undervoltage Lockout
V
IN1
Undervoltage Lockout Release
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
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.
CONDITIONS
V
RUN/SS
= 0V
V
RUN/SS
= 4.5V, V
FB
= 0V
V
IN1
Falling
V
IN1
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
I
CC
= 0mA to 20mA
V
FB1
Rising
V
FB1
Falling
V
FB1
Returning
I
PGOOD
= 5mA
5.5
– 5.5
q
q
q
MIN
– 0.5
0.8
TYP
– 1.2
1.8
3.4
3.5
2
2
3
1
20
20
20
20
MAX
–3
3
3.9
4
3
3
4
2
UNITS
µA
µA
V
V
Ω
Ω
Ω
Ω
ns
ns
ns
ns
Internal V
CC
Regulator
4.7
5
–0.1
7.5
– 7.5
1
0.15
0.9
5.3
±2
9.5
– 9.5
2
0.4
1.5
10
3
0.01
0°C to 70°C
–40°C to 85°C
1.5V
≤
V
IN
≤
10V
0°C to 70°C
–40°C to 85°C
(Note 5)
I
SW
= 300mA
V
SW
= 5V
1
0.3
V
SHDN
= 3V
V
SHDN
= 0V
25
0.01
50
0.1
q
q
q
V
%
%
%
%
V
V
V
mA
µA
V
V
nA
%/V
MHz
MHz
%
mA
4.5
1
1.255
1.260
80
0.2
1.8
1.9
V
FB2
I
VFB2
∆V
FB2(LINEREG)
f
BOOST
DC
BOOST(MAX)
I
LIM(BOOST)
V
CESAT(BOOST)
I
SWLKG(BOOST)
V
SHDN(HIGH)
V
SHDN(LOW)
I
SHDN
1.205
1.200
1.23
27
0.02
1.0
0.9
82
500
1.4
86
800
300
0.01
350
1
mV
µA
V
V
µA
µA
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.
3713fa
3
LTC3713
TYPICAL PERFOR A CE CHARACTERISTICS
Transient Response
Transient Response
(Discontinuous Mode)
Start-Up from Shutdown
V
OUT
100mV/DIV
I
L
5A/DIV
50µs/DIV
LOAD STEP 0A TO 6A
V
IN
= 3.3V
V
OUT
= 1.25V
FCB = 0V
FIGURE 1 CIRCUIT
Boost Converter Oscillator
Frequency vs Temperature
2.00
1.75
V
IN
= 5V
SHDN PIN BIAS CURRENT (µA)
40
50
SWITCHING FREQUENCY (MHz)
CURRENT LIMIT (mA)
1.50
1.25
1.00
0.75
0.50
0.25
0
–50
V
IN
= 1.5V
–25
0
25
50
TEMPERATURE (°C)
V
FB2
, Feedback Pin Voltage
1.25
100
90
FEEDBACK PIN VOLTAGE (V)
1.24
VOLTAGE
EFFICIENCY (%)
1.23
80
70
60
50
V
IN
= 3.3V
EFFICIENCY (%)
1.22
1.21
40
FIGURE 1 CIRCUIT (B)
1.20
–50
–25
0
25
50
TEMPERATURE (°C)
4
U W
75
75
V
OUT
100mV/DIV
V
OUT
500mV/DIV
I
L
5A/DIV
I
L
5A/DIV
3713 G01
50µs/DIV
LOAD STEP 600mA TO 6A
V
IN
= 3.3V
V
OUT
= 1.25V
FCB = INTV
CC
FIGURE 1 CIRCUIT
3713 G02
500µs/DIV
V
IN
= 3.3V
V
OUT
= 1.25V
L = 1.8µH
C
OUT
= 540µF
LOAD = 0.2Ω
3713 G03
SHDN Pin Current vs V
SHDN
1000
T
A
= 25°C
900
800
Boost Converter Current Limit
vs Duty Cycle
70°C
700
600
500
400
300
–40°C
25°C
30
20
10
0
100
3713 G04
200
0
1
2
3
4
SHDN PIN VOLTAGE (V)
5
3713 G05
10
20
30
40
50
60
DUTY CYCLE (%)
70
80
3713 G06
Efficiency vs Load Current
(Discontinuous Mode)
100
90
V
IN
= 2.5V
80
70
60
50
40
30
20
10
Efficiency vs Load Current
(Force Continuous)
V
IN
= 2.5V
V
IN
= 3.3V
FIGURE 1 CIRCUIT (B)
10
0
0.01
0.05
0.8
0.09 0.4
3
LOAD CURRENT (A)
7
3713 G10
100
3713 G07
30
0.01 0.04 0.07 0.1 0.4 0.7 1
4
LOAD CURRENT (A)
7
1713 G09
3713fa
LTC3713
TYPICAL PERFOR A CE CHARACTERISTICS
Load Regulation
0
–0.1
350
300
LOAD = 6A
FREQUENCY (kHz)
–0.2
–0.3
–0.4
–0.5
–0.6
FIGURE 1 CIRCUIT
–0.7
0
1
2
3 4 5 6
7
LOAD CURRENT (A)
8
9
10
200
150
100
50
FIGURE 1 CIRCUIT
0
1.5
ON-TIME (ns)
∆V
OUT
(%)
On-Time vs V
ON
Voltage
1000
I
ION
= 30µA
300
250
200
150
100
200
50
MAXIMUM CURRENT SENSE THRESHOLD (mV)
800
ON-TIME (ns)
600
ON-TIME (ns)
400
0
0
2
1
V
ON
VOLTAGE (V)
Maximum Current Sense
Threshold vs V
RNG
Voltage
MAXIMUM CURRENT SENSE THRESHOLD (mV)
MAXIMUM CURRENT SENSE THRESHOLD (mV)
V
RNG
= 1V
MAXIMUM CURRENT SENSE THRESHOLD (mV)
300
250
200
150
100
50
0
0.5
0.75
1.0
1.25
1.5
V
RNG
VOLTAGE (V)
U W
3713 G11
Frequency vs Input Voltage
10k
On-Time vs I
ON
Current
V
VON
= 0V
250
LOAD = 0A
1k
100
10
2.0
4.0
2.5 3.0 3.5
INPUT VOLTAGE (V)
4.5
5.0
1
10
I
ON
CURRENT (µA)
100
3713 G13
3713 G12
On-Time vs Temperature
I
ION
= 30µA
150
125
100
75
50
25
0
Current Limit Foldback
V
RNG
= 1V
3
3713 G14
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
0
0.2
0.4
V
FB
(V)
0.6
0.8
3713 G16
3713 G15
Maximum Current Sense
Threshold vs RUN/SS Voltage
150
125
100
75
50
25
0
1.5
2
2.5
3
RUN/SS VOLTAGE (V)
3.5
3713 G18
Maximum Current Sense
Threshold vs Temperature
150
V
RNG
= 1V
140
130
120
110
1.75
2.0
100
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
3713 G17
3713 G19
3713fa
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