LT1619
Low Voltage Current Mode
PWM Controller
FEATURES
s
s
s
s
DESCRIPTIO
s
s
s
s
s
s
s
Wide V
IN
Range: 1.9V to 18V
300kHz Fixed Frequency Current Mode Control
1A Rail-to-Rail N-Channel MOSFET Driver
Low 53mV Current Limit Threshold Voltage
Improves Efficiency
Implements Boost, SEPIC and Flyback Converters
Requiring Low Side Power Transistors
Internal Current Sense Amplifier
with Leading Edge Blanking
Up to 500kHz External Synchronization
Burst Mode
®
Operation for High Efficiency
at Light Load
140µA Quiescent Current
15µA Shutdown Current
8-Lead MSOP and SO Packages
The LT
®
1619 is a fixed frequency PWM controller for
implementing current mode DC/DC converters with mini-
mum external parts. The LT1619 operates with input
voltages ranging from 1.9V to 18V and is suitable for a
variety of battery-powered and distributed DC/DC con-
verters. The internal rail-to-rail N-channel MOSFET driver
operates either from the input in the nonbootstrapped
mode or from the output in bootstrapped operation. The
driver is designed to drive a low side power transistor in
boost, SEPIC, flyback and other topologies.
Converter efficiency is improved at heavy loads with a
53mV current sense voltage and at light load with Burst
Mode operation. The operating frequency is internally set
at 300kHz. The oscillator can also be synchronized exter-
nally up to 500kHz. No load quiescent current is 140µA and
shutdown current is 15µA.
The LT1619 is available in 8-lead MSOP and SO packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
APPLICATIO S
s
s
s
3.3V to 5V DC/DC Converters
Distributed Power Supplies
Isolated Power Supplies
TYPICAL APPLICATIO
V
IN
3.3V
37.4k
12.4k
1
2
3
S/S
FB
V
C
GND
V
IN
DRV
LT1619
GATE
SENSE
8
7
6
5
0.1µF
+
EFFICIENCY (%)
C1
22µF
0.1µF
L1
5.6µH
5A
V
OUT
5V
2.2A
M1
Si9804
D1
75k
220pF
15nF
4
+
C
OUT
440µF
R
SENSE
0.01Ω
1619 F01
C1: PANASONIC EEFCDOK220R
C
OUT
: KEMET T495X227K010AS (×2)
D1: MBRD835L
L1: COILCRAFT DO5022P-562
Figure 1. High Efficiency 3.3V to 5V DC/DC Converter
1619fa
U
Efficiency
95
90
85
80
75
70
1
10
100
LOAD CURRENT (mA)
1000
1619 F01a
U
U
1
LT1619
ABSOLUTE
AXI U
RATI GS
Input Voltage (V
IN
) ................................... – 0.3V to 20V
Gate Drive Supply Voltage (DRV) ............. – 0.3V to 20V
Shutdown/Synch Voltage (S/S) ................ – 0.3V to 20V
Feedback Voltage (FB) .............................................. V
IN
Compensation Voltage (V
C
) ...................................... 3V
Gate Drive Output Current (GATE) ........................
±1.5A
PACKAGE/ORDER I FOR ATIO
TOP VIEW
S/S
FB
V
C
GND
1
2
3
4
8
7
6
5
V
IN
DRV
GATE
SENSE
ORDER PART
NUMBER
LT1619EMS8
S/S 1
FB 2
V
C
3
MS8 PACKAGE
8-LEAD PLASTIC MSOP
MS8 PART MARKING
LTHC
T
JMAX
= 125°C,
θ
JA
= 200°C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
IN
= V
DRV
= 2.5V, V
S/S
= V
IN
, COMP open, V
SENSE
= 0V unless otherwise noted.
PARAMETER
Reference Voltage
Reference Line Regulation
FB Input Bias Current
Error Amplifier Transconductance
Error Amplifier Output Source Current
Error Amplifier Output Sink Current
Error Amplifier Clamp Voltage
Undervoltage Lockout Threshold
Input Voltage Range
Switching Frequency
Synchronization Frequency Range
Maximum Duty Cycle
Current Limit Threshold
Burst Mode Operation Current Limit
q
q
q
CONDITIONS
Measured at the FB Pin
1.9V
≤
V
IN
≤
18V
V
FB
= V
REF
q
V
FB
= 1V, V
COMP
= 1V
V
FB
= 1.5V, V
COMP
= 1V
V
FB
= 1V
1.9V
≤
V
IN
≤
18V
2
U
U
W
W W
U
W
(Note 1)
Current Sense Voltage (SENSE) ................. – 0.5V to V
IN
Operating Temperature Range (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
TOP VIEW
8
7
6
5
V
IN
DRV
GATE
SENSE
ORDER PART
NUMBER
LT1619ES8
GND 4
S8 PART MARKING
1619
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 120°C/ W
MIN
1.22
TYP
1.24
0.004
10
MAX
1.26
0.05
25
260
14
14
2.2
1.85
18
UNITS
V
%/V
nA
µΩ
–1
µA
µA
V
V
V
kHz
kHz
%
mV
mV
80
4
4
1.6
1.65
1.9
220
370
88
40
q
170
8.7
8.7
300
92
53
10
360
500
66
1619fa
LT1619
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
IN
= V
DRV
= 2.5V, V
S/S
= V
IN
, COMP open, V
SENSE
= 0V unless otherwise noted.
PARAMETER
Current Sense Input Current
Current Limit Delay
Driver Output Rise Time
Driver Output Fall Time
Driver Output High Level
Driver Output Low Level
Shutdown Driver Output Level
Idle Mode Driver Output Level
S/S Pin Current
Operating Supply Current
Quiescent Supply Current
Shutdown Supply Current
Shutdown Threshold
Shutdown Delay
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2:
The LT1619E 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.
C
L
= 3300pF
C
L
= 3300pF
I
OUT
= – 20mA
I
OUT
= – 200mA
I
OUT
= 20mA
I
OUT
= 200mA
V
S/S
= 0V, I
OUT
= 20mA
V
S/S
= V
IN
, V
FB
= 1.5V, I
OUT
= 20mA
V
S/S
= V
IN
V
S/S
= 0V
V
FB
= 1V
V
S/S
= V
IN
, V
FB
= 1.5V
V
S/S
= 0V
V
S/S
= 0V, V
IN
= 18V, T
A
= 85°C
0.45
12
17
q
CONDITIONS
V
SENSE
= 0V
q
MIN
– 90
TYP
– 120
150
30
35
MAX
– 150
UNITS
µA
ns
ns
ns
V
V
V
DRV
– 0.6
V
DRV
– 1.6
V
DRV
– 0.35
V
DRV
– 1.2
100
0.5
100
100
200
0.7
200
200
4
–2
9
140
15
40
220
19
1.2
33
mV
V
mV
mV
µA
µA
mA
µA
µA
µA
V
µs
Note 3:
T
J
is calculated from the ambient temperature T
A
, the power
dissipation P
D
and the thermal resistance
θ
JA
of the package according to
the formula:
T
J
= T
A
+ P
D
•
θ
JA
TYPICAL PERFOR A CE CHARACTERISTICS
Bandgap Voltage vs Temperature
1.245
1.243
1.241
BANDGAP VOLTAGE (V)
V
IN
= 2.5V
1.239
I
S/S
(µA)
1.237
1.235
1.233
1.231
2
1
0
–1
T
A
= 85°C
S/S PIN CURRENT (µA)
1.229
1.227
1.225
–40 –20
0
20
40
60
80
100 120
1619 G01
TEMPERATURE (°C)
U W
I
S/S
vs V
S/S
5
T
A
= –40°C
4
3
T
A
= 25°C
4
5
S/S Pin Current vs Temperature
V
S/S
= 2.5V
3
2
1
0
–1
–2
V
S/S
= 0V
–2
–3
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
V
S/S
(V)
1619 G02
–3
–40 –20
0
20 40 60 80
TEMPERATURE (°C)
100 120
1619 G03
1619fa
3
LT1619
TYPICAL PERFOR A CE CHARACTERISTICS
Shutdown Supply Current
vs Input Voltage
45
IDLE MODE SUPPLY CURRENT (µA)
40
SUPPLY CURRENT (µA)
DEVIATION FROM NOMINAL FREQUENCY (%)
35
T
A
= –40°C
30
T
A
= 25°C
25
20
15
10
5
0
2
4
6 8 10 12 14 16 18 20
INPUT VOLTAGE (V)
1619 G04
T
A
= 85°C
Maximum Duty Ratio
vs Temperature
95
V
IN
= 2.5V
8
6
4
2
0
–2
–4
FREQUENCY DEVIATION (%)
94
CURRENT LIMIT THRESHOLD (mV)
DUTY RATIO (%)
93
92
91
90
–40
–20
40
20
0
60
TEMPERATURE (°C)
Burst Mode Operation Current
Limit Threshold vs Temperature
14
CURRENT LIMIT THRESHOLD (mV)
V
IN
= 2.5V
12 DUTY CYCLE = 0
SENSE PIN CURRENT (µA)
SENSE PIN CURRENT (µA)
10
8
6
4
2
0
–40 –20
40
20
60
0
TEMPERATURE (°C)
4
U W
80
1619 G07
Idle Mode Supply Current
vs Temperature
200
190
180
170
160
150
140
–40 –20
V
IN
= 2.5V
Frequency Deviation from
Nominal vs Temperature
10
8
6
4
2
0
–2
–4
–6
–8
–10
– 40 – 20
0
60
40
20
TEMPERATURE (°C)
80
100
1619 G06
V
IN
= 2.5V
NOMINAL FREQUENCY = 300kHz
0
20 40 60 80
TEMPERATURE (°C)
100 120
1619 G05
Deviation from Nominal
Frequency vs Input Voltage
T
A
= 25°C
NOMINAL FREQUENCY = 300kHZ
58
57
56
55
54
53
52
51
Current Limit Threshold
vs Temperature
V
IN
= 2.5V
100
0
2
4
6 8 10 12 14 16 18 20
INPUT VOLTAGE (V)
1619 G08
50
–40 – 20
0
60
40
20
TEMPERATURE (°C)
80
100
1619 G09
SENSE Pin Input Bias Current
vs Temperature
–115
–117
–119
–121
–123
–125
–127
–129
–131
–133
V
SENSE
= 0V
– 90
– 95
–100
–105
–110
–115
–120
–125
40
0
60
20
TEMPERATURE (°C)
80
100
SENSE Pin Input Bias Current
vs Sense Voltage
T
A
= 25°C
80
100
–135
–40 –20
–130
–10
0
10
20
30
40
50
60
V
SENSE
(mV)
1619 G11
1619 G12
1619 G10
1619fa
LT1619
PI FU CTIO S
S/S (Pin 1):
Shutdown and Synchronization. Shutdown is
active low with a typical threshold voltage of 0.9V. For
normal operation, the S/S pin is tied to V
IN
. To externally
synchronize the controller, drive the S/S pin with pulses.
FB (Pin 2):
The inverting Input of the Error Amplifier.
Connect the resistor divider tap here. Set V
OUT
according
to V
OUT
= 1.24(1 + R1/R2). See Figure 1.
V
C
(Pin 3):
Compensation Pin for the Error Amplifier. V
C
is
the output of the transconductance amplifier. Overall loop
is compensated with an RC network from this pin to the
ground.
GND (Pin 4):
Ground. Connect to local ground plane.
SENSE (Pin 5):
The Input of the Current Sense Amplifier.
The SENSE pin is connected to the source of the N-channel
MOSFET and to a sense resistor to the ground. The current
limit threshold is internally set at 53mV, giving a maximum
switch current of 53mV/R
SENSE
.
GATE (Pin 6):
The Output of the MOSFET Driver.
DRV (Pin 7):
The Pull-Up Supply of the MOSFET Driver. Tie
this pin to V
IN
(Pin 8) for nonbootstrapped operation or to
the converter output for bootstrapped operation.
V
IN
(Pin 8):
Supply or Battery Input. Must be closely
bypassed to the ground plane.
BLOCK DIAGRA
V
C
3
ERROR
AMPLIFIER
1.24V
1.8V
+
g
m
FB 2
–
V
B
+
Σ
+
CLK
CURRENT
SENSE
AMP
S/S 1
+
SHUTDOWN
DELAY
REF/BIAS
CURRENT
LIMIT
COMPARATOR
–
I
LIM
1619 F02
Figure 2. LT1619 Block Diagram
1619fa
+
RAMP COMP
300kHz
SYNC
OSCILLATOR
–
W
+
–
U
U
U
V
IN
8
–
A2
UVLO
+
–
A1
IDLE
+
V
IN
DRV
7
C1
S
Q
R
DRIVER
6
GATE
LOAD
R
SENSE
5
SENSE
4
280ns
LEADING
EDGE
BLANKING
GND
5
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