FEATURES
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LTC3723-1/LTC3723-2
Synchronous Push-Pull
PWM Controllers
DESCRIPTIO
The LTC
®
3723-1/LTC3723-2 synchronous push-pull PWM
controllers provide all of the control and protection func-
tions necessary for compact and highly efficient, isolated
power converters. High integration minimizes external
component count, while preserving design flexibility.
The robust push-pull output stages switch at half the
oscillator frequency. Dead-time is independently pro-
grammed with an external resistor. Synchronous rectifier
timing is adjustable to optimize efficiency. A UVLO pro-
gram input provides precise system turn-on and turn off
voltages. The LTC3723-1 features peak current mode
control with programmable slope compensation and lead-
ing edge blanking, while the LTC3723-2 employs voltage
mode control with voltage feedforward capability.
The LTC3723-1/LTC3723-2 feature extremely low operat-
ing and start-up currents. Both devices provide reliable
short-circuit and overtemperature protection. The
LTC3723-1/LTC3723-2 are offered in a 16-pin SSOP
package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
High Efficiency Synchronous Push-Pull PWM
1.5A Sink, 1A Source Output Drivers
Supports Push-Pull, Full-Bridge, Half-Bridge, and
Forward Topologies
Adjustable Push-Pull Dead-Time and Synchronous
Timing
Adjustable System Undervoltage Lockout and
Hysteresis
Adjustable Leading Edge Blanking
Low Start-Up and Quiescent Currents
Current Mode (LTC3723-1) or Voltage Mode
(LTC3723-2) Operation
Single Resistor Slope Compensation
V
CC
UVLO and 25mA Shunt Regulator
Programmable Fixed Frequency Operation to 1MHz
50mA Synchronous Output Drivers
Soft-Start, Cycle-by-Cycle Current Limiting and
Hiccup Mode Short-Circuit Protection
5V, 15mA Low Dropout Regulator
Available in 16-Pin SSOP Package
APPLICATIO S
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Telecommunications, Infrastructure Power Systems
Distributed Power Architectures
TYPICAL APPLICATIO
V
IN
Isolated Push-Pull Converter
V
OUT
UVLO
DRVA
ME
FROM
AUXILIARY
WINDING
•
SPRG
V
CC
DRVB
CS
•
SYNC
LTC3901
MF
V
REF
DPRG
C
T
R
LEB
SDRA
SDRB
V
REF
LTC3723-1
V
OUT
V
REF
SS
COMP
FB GND
U
U
U
V
OUT
V
+
COLL
LT1431
GND-F GND-S
R
REF
372312 TA01
372312f
1
LTC3723-1/LTC3723-2
ABSOLUTE
AXI U RATI GS
V
CC
to GND (Low Impedance Source) .......– 0.3V to 10V
(Chip Self-Regulates at 10.3V)
UVLO to GND ............................................. – 0.3V to V
CC
All Other Pins to GND
(Low Impedance Source) .........................– 0.3V to 5.5V
V
CC
(Current Fed) ................................................. 40mA
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
REF
SDRB
SDRA
DRVB
V
CC
DRVA
GND
C
T
1
2
3
4
5
6
7
8
16 SPRG
15 UVLO
14 SS
13 FB
12 R
LEB
11 COMP
10 CS
9
DPRG
GN PACKAGE
16-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 100°C/W
ORDER PART NUMBER
LTC3723EGN-1
GN PART MARKING
37231
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 9.5V unless otherwise noted.
SYMBOL
Input Supply
V
CCUV
V
CCHY
I
CCST
I
CCRN
V
SHUNT
R
SHUNT
SUVLO
SHYST
ROS
I
RMP
V
CC
Undervoltage Lockout
V
CC
UVLO Hysteresis
Start-Up Current
Operating Current
Shunt Regulator Voltage
Shunt Resistance
System UVLO Threshold
System UVLO Hysteresis Current
Ramp Offset Voltage
Ramp Discharge Current
Measured on V
CC
Measured on V
CC
V
CC
= V
UVLO
– 0.3V
No Load on Outputs
Current into V
CC
= 10mA
Current into V
CC
= 10mA to 17mA
Measured on UVLO Pin, 10mA into V
CC
Current Flows Out of UVLO Pin, 10mA into V
CC
Measured on COMP, RAMP = 0V
RAMP = 1V, COMP = 0V, C
T
= 4V, 3723-1 Only
4.8
8.5
●
ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
Pulse Width Modulator
0.65
50
V
mA
372312f
2
U
U
W
W W
U
W
(Note 1)
V
REF
Output Current ............................... Self-Regulated
Operating Temperature (Notes 5,6)
LTC3723E ........................................... – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 125°C
Lead Temperature (Soldering, 10sec)................... 300°C
TOP VIEW
V
REF
SDRB
SDRA
DRVB
V
CC
DRVA
GND
C
T
1
2
3
4
5
6
7
8
16 SPRG
15 UVLO
14 SS
13 FB
12 DPRG
11 COMP
10 CS
9
RAMP
GN PACKAGE
16-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 100°C/W
ORDER PART NUMBER
LTC3723EGN-2
GN PART MARKING
37232
MIN
TYP
10.25
MAX
10.7
230
8
10.8
3.5
5.2
11.5
UNITS
V
V
µA
mA
V
Ω
V
µA
3.8
4.2
145
3
10.3
1.4
5.0
10
LTC3723-1/LTC3723-2
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 9.5V unless otherwise noted.
SYMBOL
I
SLP
DCMAX
DCMIN
DTADJ
Oscillator
OSCI
OSCT
OSCV
V
FB
FB
I
AVOL
I
IB
V
OH
V
OL
I
SOURCE
I
SINK
Reference
V
REF
REFLD
REFLN
REFTV
REFSC
DRVH(x)
DRVL(x)
RDH(x)
RDL(x)
TDR(x)
TDF(x)
OUTH(x)
OUTL(x)
RHI(x)
RLO(x)
TR(x)
TF(x)
CLPP
CLSD
CLDEL
Initial Accuracy
Load Regulation
Line Regulation
Total Variation
Short-Circuit Current
Output High Voltage
Output Low Voltage
Pull-Up Resistance
Pull-Down Resistance
Rise-Time
Fall-Time
Output High Voltage
Output Low Voltage
Pull-Up Resistance
Pull-Down Resistance
Rise-Time
Fall-Time
Pulse by Pulse Current Limit Threshold
Shutdown Current Limit Threshold
Current Limit Delay to Output
T
A
= 25°C, Measured on V
REF
Load on V
REF
= 100µA to 5mA
V
CC
= 6.5V to 9.5V
Line, Load and Temperature
V
REF
Shorted to GND
I
OUT(x)
= –100mA
I
OUT(x)
= 100mA
I
OUT(x)
= –10mA to –100mA
I
OUT(x)
= –10mA to –100mA
C
OUT(x)
= 1nF
C
OUT(x)
= 1nF
I
OUT(x)
= –30mA
I
OUT(x)
= 30mA
I
OUT(x)
= –10mA to -30mA
I
OUT(x)
= –10mA to -30mA
C
OUT(x)
= 50pF
C
OUT(x)
= 50pF
Measured on CS
Measured on CS
100mV Overdrive on CS, (Note 2)
280
475
9.0
●
ELECTRICAL CHARACTERISTICS
PARAMETER
Slope Compensation Current
Maximum Duty Cycle
Minimum Duty Cycle
Dead-Time
Initial Accuracy
V
CC
Variation
C
T
Ramp Amplitude
FB Input Voltage
FB Input Range
Open-Loop Gain
Input Bias Current
Output High
Output Low
Output Source Current
Output Sink Current
CONDITIONS
Measured on CS, C
T
= 1V, 3723-1 Only
C
T
= 2.25V
COMP = 4.5V
COMP = 0V
●
●
MIN
TYP
30
68
MAX
UNITS
µA
µA
47
48.2
0
130
50
%
%
ns
T
A
= 25°C, C
T
= 270pF
V
CC
= 6.5V to 9.5V, Overtemperature
Measured on C
T
COMP = 2.5V, (Note 3)
Measured on FB, (Note 4)
COMP = 1V to 3V, (Note 3)
COMP = 2.5V, (Note 3)
Load on COMP = –100µA
Load on COMP = 100µA
COMP = 2.5V
COMP = 2.5V
●
220
–3
250
2.35
280
3
kHz
%
V
Error Amplifier
1.172
– 0.3
70
4.7
400
2
4.925
90
5
4.92
0.27
700
5
5.00
2
1
4.900
18
9.0
5.000
30
9.2
0.17
2.9
1.7
10
10
9.2
0.44
11
15
10
10
300
600
80
320
725
0.6
15
20
0.6
4
2.5
5.075
15
10
5.100
45
0.5
50
1.2
1.22
2.5
V
V
dB
nA
V
V
µA
mA
V
mV
mV
V
mA
V
V
Ω
Ω
ns
ns
V
V
Ω
Ω
ns
ns
mV
mV
ns
372312f
Push-Pull Outputs
Synchronous Outputs
Current Limit and Shutdown
3
LTC3723-1/LTC3723-2
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 9.5V unless otherwise noted.
SYMBOL
SSI
SSR
FLT
PARAMETER
Soft-Start Current
Soft-Start Reset Threshold
Fault Reset Threshold
CONDITIONS
SS = 2.5V
Measured on SS
Measured on SS
MIN
10
0.7
4.5
TYP
13
0.4
4.2
MAX
16
0.1
3.5
UNITS
µA
V
V
ELECTRICAL CHARACTERISTICS
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
Includes leading edge blanking delay, R
LEB
= 20k, not tested in
production.
Note 3:
FB is driven by a servo loop amplifier to control V
COMP
for these
tests.
Note 4:
Set FB to –0.3V, 2.5V and insure that COMP does not phase invert.
Note 5:
The LTC3723E–1/LTC3723E-2 are 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 6:
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
TYPICAL PERFOR A CE CHARACTERISTICS
Start-Up I
CC
vs V
CC
200
150
100
10.00
FREQUENCY (kHz)
I
CC
(µA)
V
CC
(V)
50
0
0
2
4
V
CC
(V)
6
Leading Edge Blanking Time
vs R
LEB
350
300
250
BLANK TIME (ns)
V
REF
(V)
200
150
100
V
REF
(V)
50
0
0 10 20 30 40 50 60
R
LEB
(kΩ)
70 80 90 100
372312 G04
4
U W
8
(T
A
= 25°C unless otherwise noted)
Oscillator Frequency vs
Temperature
260
C
T
= 270pF
V
CC
vs I
SHUNT
10.50
10.25
250
240
9.75
230
9.50
10
372312 G01
0
10
30
20
I
SHUNT
(mA)
40
50
372312 G02
220
– 60 – 40 – 20 0
20 40 60
TEMPERATURE (°C)
80
100
372312 G03
V
REF
vs I
REF
5.05
T
J
= 25°C
V
REF
vs Temperature
5.01
5.00
5.00
T
J
= 85°C
4.95
4.99
4.90
T
J
= –40°C
4.85
4.98
4.80
0
5
10
15 20
25
I
REF
(mA)
30
35
40
4.97
– 60 – 40 – 20 0
20 40 60
TEMPERATURE (°C)
80
100
372312 G05
372312 G06
372312f
LTC3723-1/LTC3723-2
TYPICAL PERFOR A CE CHARACTERISTICS
Error Amplifier Gain/Phase
190
DELAY (ns)
I
CC
(µA)
100
80
60
40
20
0
–180
–270
–360
10
100
1k
10k
100k
FREQUENCY (Hz)
1M
10M
GAIN (dB)
PHASE (DEG)
Slope Current vs Temperature
90
80
70
C
T
= 2.25V
10.5
10.4
SHUNT VOLTAGE (V)
CURRENT (µA)
60
50
40
30
20
10
0
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
C
T
= 1V
10.2
10.1
10.0
9.9
9.8
–55
DELAY (ns)
FB Input Voltage vs Temperature
1.205
1.204
1.203
FB VOLTAGE (V)
1.201
1.200
1.199
1.198
1.197
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
DELAY (ns)
1.202
U W
(T
A
= 25°C unless otherwise noted)
LTC3723 Deadtime vs R
DPRG
With and Without 200k Prebias
Compensation
275
250
225
200k PREBIAS
200
175
150
125
100
75
50
NO 200k PREBIAS
Start-Up I
CC
vs Temperature
180
170
160
150
140
130
120
110
100
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
0
50 100 150 200 250 300 350 400 450 500
R
DPRG
(kΩ)
372312 G09
372312 G07
372312 G08
V
CC
Shunt Voltage vs
Temperature
I
CC
= 10mA
900
800
700
10.3
600
500
400
300
200
100
0
–25
5
35
65
TEMPERATURE (°C)
95
125
Synchronous Driver Turn-Off Delay
vs R
SPRG
Referenced to CT Peak
0
50
150
200
100
R
SPRG
(kΩ)
250
300
372312 G10
372312 G11
372312 G12
Synchronous Driver Turn-Off
Delay vs R
SPRG
Referenced to
Push-Pull Driver Outputs
350
300
250
200
150
100
50
0
–50
0
50
100
150
200
R
SPRG
(kΩ)
250
300
R
DPRG
= 150k
372312 G13
372312 G14
372312f
5
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