FEATURES
s
s
LTC1922-1
Synchronous Phase
Modulated Full-Bridge Controller
DESCRIPTIO
The LTC
®
1922-1 phase shift PWM controller provides all
of the control and protection functions necessary to imple-
ment a high performance, zero voltage switched, phase
shift, full-bridge power converter with synchronous recti-
fication. The part is ideal for developing isolated, low
voltage, high current outputs from a high voltage input
source. The LTC1922-1 combines the benefits of the full-
bridge topology with fixed frequency, zero voltage switch-
ing operation (ZVS). Adaptive ZVS circuity controls the
turn-on signals for each MOSFET independent of internal
and external component tolerances for optimal perfor-
mance.
The LTC1922-1 also provides secondary side synchro-
nous rectifier control. The device uses peak current mode
control with programmable slope comp and leading edge
blanking.
The LTC1922-1 features extremely low operating and
start-up currents to simplify off-line start-up and bias
circuitry. The LTC1922-1 also includes a full range of
protection features and is available in 20-pin through hole
(N) and surface mount (G) packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
DirectSense is a trademark of Linear Technology Corporation.
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Adaptive DirectSense
TM
Zero Voltage Switching
Integrated Synchronous Rectification Control for
Highest Efficiency
Output Power Levels from 50W to Kilowatts
Very Low Start-Up and Quiescent Currents
Compatible with Voltage Mode and Current Mode
Topologies
Programmable Slope Compensation
Undervoltage Lockout Circuitry with 4.2V Hysteresis
and Integrated 10.3V Shunt Regulator
Fixed Frequency Operation to 1MHz
50mA Outputs for Bridge Drive and Secondary Side
Synchronous Rectifiers
Soft-Start, Cycle-by-Cycle Current Limiting and
Hiccup Mode Short-Circuit Protection
5V, 15mA Low Dropout Regulator
20-Pin PDIP and SSOP Packages
APPLICATIO S
s
s
s
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Telecommunications, Infrastructure Power Systems
Distributed Power Architectures
Server Power Supplies
High Density Power Modules
TYPICAL APPLICATIO
BIAS
SUPPLY
V
IN
48V
V
OUT
3.3V
EFFICIENCY (%)
LTC1922-1
ISOLATED
FEEDBACK
1922 TA01a
U
U
U
Efficiency
100
90
V
IN
= 48V
V
IN
= 36V
80
70
60
0
10
20
LOAD CURRENT (A)
30
40
1922 • TA01b
1
LTC1922-1
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SYNC
RAMP
CS
COMP
R
LEB
FB
SS
PDLY
SBUS
1
2
3
4
5
6
7
8
9
20 C
T
19 GND
18 OUTA
17 OUTB
16 OUTC
15 V
CC
14 OUTD
13 OUTE
12 OUTF
11 V
REF
N PACKAGE
20-LEAD PDIP
V
CC
to GND
Low Impedance Source ......................... –0.3V to 10V
(Chip Self Regulates at 10.3V)
All Other Pins to GND
(Low Impedance Source) ..................... –0.3V to 5.5V
V
CC
(Current Fed) .................................................. 25mA
V
REF
Output Current ................................ Self Regulated
Outputs (A, B, C, D, E, F) Current .....................
±100mA
Operating Temperature Range (Note 5)
LTC1922E ........................................... – 40°C to 85°C
LTC1922I ............................................ – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 125°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LTC1922EG-1
LTC1922IG-1
LTC1922EN-1
LTC1922IN-1
ADLY 10
G PACKAGE
20-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 110°C/W (G)
T
JMAX
= 125°C,θ
JA
= 62°C/W (N)
Consult factory for parts specified with wider operating temperature ranges.
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at V
CC
= 9.5V, C
T
= 180pF, T
A
= T
MIN
to T
MAX
unless other wise noted.
SYMBOL
Input Supply
UVLO
UVHY
I
CCST
I
CCRN
V
SHUNT
R
SHUNT
Delay Blocks
DTHR
DHYS
DTMO
DZRT
Phase Modulator
ROS
I
RMP
I
SLP
DCMX
DCMN
RAMP Offset Voltage
RAMP Discharge Current
Slope Compensation Current
Maximum Phase Shift
Minimum Phase Shift
Measured on COMP, RAMP = 0V
RAMP = 1V, COMP = 0V
Measured on CS, C
T
= 1.5V
C
T
= 3V
COMP = 4V
COMP = 0V
q
q
ELECTRICAL CHARACTERISTICS
PARAMETER
Undervoltage Lockout
UVLO Hysteresis
Start-Up Current
Operating Current
Shunt Regulator Voltage
Shunt Resistance
Delay Pin Threshold
ADLY and PDLY
Delay Hysteresis Current
ADLY and PDLY
Delay Time-Out
Zero Delay Threshold
CONDITIONS
Measured on V
CC
Measured on V
CC
V
CC
= V
UVLO
– 0.3V
Current Into V
CC
= 10mA
Current Into V
CC
= 7mA to 17mA
SBUS = 1.5V
SBUS = 2.25V
SBUS = 1.5V, ADLY/PDLY = 1.6V
SBUS = 1.5V
SBUS = 2.25V
Measured on SBUS
q
MIN
TYP
10.25
MAX
10.7
250
7
10.8
2
1.62
2.42
1.45
UNITS
V
V
µA
mA
V
Ω
V
V
mA
ns
ns
3.8
4.2
145
4
10.2
–1.5
1.38
2.08
1.1
1.50
2.25
1.3
600
900
3
4.15
0.4
5
30
35
70
95
50
55
110
99.5
0.1
0.6
75
150
2
U
V
V
mA
µA
µA
%
%
W
U
U
W W
W
LTC1922-1
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at V
CC
= 9.5V, C
T
= 180pF, T
A
= T
MIN
to T
MAX
unless other wise noted.
SYMBOL
Oscillator
OSCT
OSCV
OSYT
OSYW
OSYWX
OSOP
Error Amplifier
V
FB
FBI
AVOL
I
IB
V
OH
V
OL
I
SOURCE
I
SINK
Reference
V
REF
REFTV
REFLD
REFLN
REFSC
Outputs
OUTH(X)
OUTL(X)
R
HI(X)
R
LO(X)
t
r(X)
t
f(X)
CLPP
CLSD
SSI
SSR
FLT
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
Soft-Start Current
Soft-Start Reset Threshold
FAULT Reset Threshold
I
OUT(X)
= –50mA
I
OUT(X)
= 50mA
I
OUT(X)
= –50mA to –10mA
I
OUT(X)
= –50mA to –10mA
C
OUT(X)
= 50pF
C
OUT(X)
= 50pF
Measured on CS
Measured on CS
SS = 2.5V
Measured on SS
Measured on SS
0.34
0.55
7
0.7
4.4
7.9
8.4
0.6
22
12
5
5
0.415
0.64
12
0.4
4.1
1
30
20
15
15
0.48
0.73
17
0.1
3.8
V
V
Ω
Ω
ns
ns
V
V
µA
V
V
Initial Accuracy
Total Variation
Load Regulation
Line Regulation
Short-Circuit Current
T
A
= 25°C, Measured on V
REF
Line, Load and Temperature
Load on V
REF
= 100µA to 5mA
V
CC
= 6.5V to 9.5V
V
REF
Shorted to GND
18
q
ELECTRICAL CHARACTERISTICS
PARAMETER
Total Variation
C
T
RAMP Amplitude
SYNC Threshold
Minimum SYNC Pulse Width
Maximum SYNC Pulse Width
SYNC Output Pulse Width
FB Input Voltage
FB Input Range
Open-Loop Gain
Input Bias Current
Output High
Output Low
Output Source Current
Output Sink Current
CONDITIONS
V
CC
= 6.5V to 9.5V
Measured on C
T
Measured on SYNC
Measured at Outputs (Note 2)
Measured on Outputs, C
T
= 180pF
Measured on SYNC, R
SYNC
= 5.1k
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
q
MIN
236
3.6
1.6
TYP
277
3.85
1.8
6
MAX
319
4.2
2.2
1.3
UNITS
kHz
V
V
ns
µs
ns
170
1.179
–0.3
70
4.7
– 400
3
4.925
4.9
90
5
4.92
0.18
– 800
7
5
5
2
0.1
30
5.075
5.1
15
10
45
0.4
50
1.204
1.229
2.5
V
V
dB
nA
V
V
µA
mA
V
V
mV
mV
mA
Current Limit and Shutdown
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
SYNC pulse width is valid from >20ns and <0.4 • (1/f
OSC
),
V
SYNC
= 0V to 5V.
Note 3:
FB is driven by a servo loop amplifier to control V
COMP
for these
tests.
Note 4:
Set FB to –0.3V, 2.5 and insure that COMP does not phase invert.
Note 5:
The LTC1922-1E is guaranteed to meet performance specifications
from 0°C to 85°C. Specification over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC1922-1I is guaranteed and tested
over the – 40°C to 85°C operating temperature range.
3
LTC1922-1
TYPICAL PERFOR A CE CHARACTERISTICS
Start-Up I
CC
vs V
CC
200
T
A
= 25°C
150
FREQUENCY (kHz)
I
CC
(µA)
V
CC
(V)
100
50
0
0
2
4
V
CC
(V)
6
Leading Edge Blanking Time
vs R
LEB
350
300
250
BLANK TIME (ns)
T
A
= 25°C
200
150
100
V
REF
(V)
50
0
0 10 20 30 40 50 60
R
LEB
(kΩ)
70 80 90 100
1922 • G04
V
REF
vs Temperature
5.01
100
80
60
40
20
0
–180
–270
–360
GAIN (dB)
5.00
V
REF
(V)
4.99
PHASE (DEG)
4.98
4.97
– 60 – 40 – 20 0
20 40 60
TEMPERATURE (°C)
4
U W
8
1922 • G01
V
CC
vs I
SHUNT
10.50
T
A
= 25°C
280
Oscillator Frequency vs
Temperature
C
T
= 180pF
270
10.25
10.00
260
9.75
250
9.50
10
0
10
30
20
I
SHUNT
(mA)
40
50
1922 • G02
240
– 60 – 40 – 20 0
20 40 60
TEMPERATURE (°C)
80
100
1922 • G03
V
REF
vs I
REF
5.05
T
J
= 25°C
T
J
= 85°C
4.95
5.00
4.90
T
J
= –40°C
4.85
4.80
0
5
10
15 20 25
I
REF
(mA)
30
35
40
1922 • G05
Error Amplifier Gain/Phase
T
A
= 25°C
80
100
10
100
1k
10k
100k
FREQUENCY (Hz)
1M
10M
1922 • G03
1922 • G07
LTC1922-1
TYPICAL PERFOR A CE CHARACTERISTICS
Start-Up I
CC
vs Temperature
160
150
1.278
1.276
1.274
1.272
HYSTERESIS CURRENT (mA)
140
130
CURRENT (µA)
I
CC
(µA)
120
110
100
90
80
70
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
V
CC
Shunt Voltage vs Temperature
10.5
I
CC
= 10mA
10.4
2.4
2.3
2.2
SHUNT VOLTAGE (V)
10.3
THRESHOLD (V)
10.2
10.1
10.0
9.9
9.8
–55
–25
FB Input Voltage vs Temperature
1.202
1.201
1.200
390
385
380
FB VOLTAGE (V)
OFFSET (mV)
1.199
1.198
1.197
1.196
1.195
1.194
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
U W
1922 • G10
Delay Hysteresis Current vs
Temperature
SBUS = 1.5V
130
120
110
100
90
80
70
60
50
40
–25
5
35
65
TEMPERATURE (°C)
95
125
Slope Current vs Temperature
C
T
= 3.0V
1.270
1.268
1.266
1.264
1.262
1.260
1.258
1.256
–55
C
T
= 1.5V
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
1922 • G11
1922 • G12
Delay Pin Threshold vs
Temperature
SBUS = 2.25V
2.1
2.0
1.9
1.8
1.7
1.6
1.5
SBUS = 1.5V
5
35
65
TEMPERATURE (°C)
95
125
1.4
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
1922 • G13
1922 • G14
Ramp Offset Voltage vs
Temperature
375
370
365
360
355
350
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
1922 • G15
1922 • G16
5
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