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LTC1649CS

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16
1
LTC1649
3.3V Input High Power
Step-Down Switching
Regulator Controller
■
High Power 3.3V to 1.xV-2.xV Switching Regulator
Controller: Up to 20A Output
■
All N-Channel External MOSFETs
■
Provides 5V MOSFET Gate Drive with 3.3V Input
■
Excellent Output Regulation: ±1% Over Line, Load
and Temperature Variations
■
Constant Frequency Operation Minimizes
Inductor Size
■
High Efficiency: Over 90% Possible
■
No Low-Value Sense Resistor Needed
■
Available in 16-Lead SO Package
■
3.3V Input Power Supply for Low Voltage
Microprocessors and Logic
■
Low Input Voltage Power Supplies
■
High Power, Low Voltage Regulators
■
Local Regulation for Multiple Voltage Distributed
Power Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
The LTC
®
1649 is a high power, high efficiency switching
regulator controller optimized for use with very low supply
voltages. It operates from 2.7V to 5V input, and provides
a regulated output voltage from 1.26V to 2.5V at up to 20A
load current. A typical 3.3V to 2.5V application features
efficiency above 90% from 1A to 10A load. The LTC1649
uses a pair of standard 5V logic-level N-channel external
MOSFETs, eliminating the need for expensive P-channel
or super-low-threshold devices.
The LTC1649 shares its internal switching architecture
with the LTC1430, and features the same ±1% line, load
and temperature regulation characteristics. Current limit
is user-adjustable without requiring an external low-value
sense resistor. The LTC1649 uses a 200kHz switching
frequency and voltage mode control, minimizing external
component count and size. Shutdown mode drops the
quiescent current to below 10µA.
The LTC1649 is available in the 16-pin narrow SO package.
V
CC
V
OUT
2.5V
@15A
I
MAX
SHDN
1µF
G2
FB
V
IN
V
IN
3.3V
C
+
LTC1649
P
VCC2
P
VCC1
G1
I
FB
COMP
SS C
–
GND CP
OUT
1µF
10µF
MBR0530
0.1µF
C
C
0.01µF
IRF7801 = INTERNATIONAL RECTIFIER
MBR0530 = MOTOROLA
*12TS-1R2HL = PANASONIC
R
C
7.5k
L
EXT
*
1.2µH
C1
220pF
10µF
MBR0530
R
IMAX
50k
22Ω 1k
Q3
IRF7801
Q1, Q2
IRF7801
TWO IN
PARALLEL
C
OUT
4400µF
C
IN
3300µF
SHDN
R2
12.7k
R1
12.4k
1649 TA01
+
0.33µF
+
+
+
3.3V to 2.5V, 15A Converter LTC1649 Efficiency
LOAD CURRENT (A)
EFFICIENCY (%)
1649 TA02
0.1 1 10
100
90
80
70
60
50
40
APPLICATIO S
U
FEATURES
TYPICAL APPLICATIO
U
DESCRIPTIO
U
2
LTC1649
LTC1649CS LTC1649IS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS
V
IN
Minimum Supply Voltage Figure 1 (Note 3) ● 2.7 2.7 V
V
FB
Feedback Voltage Figure 1 ● 1.25 1.265 1.28 1.23 1.265 1.29 V
V
CPOUT
Charge Pump Output Voltage Figure 1 ● 4.8 5 5.2 4.75 5 5.25 V
I
IN
Supply Current (V
IN
)V
SHDN
= V
CC
, I
LOAD
= 0 ● 35 35 mA
V
SHDN
= 0V 10 25 10 25 µA
I
PVCC1, 2
Supply Current (P
VCC1, 2
)P
VCC
= 5V, V
SHDN
= V
CC
(Note 4) 1.5 1.5 mA
V
SHDN
= 0V 0.1 0.1 µA
f
CP
Internal Charge Pump Frequency I
CPOUT
= 20mA (Note 5) 700 700 kHz
f
OSC
Internal PWM Oscillator Frequency ● 140 200 260 130 200 325 kHz
V
IH
SHDN Input High Voltage ● 2.4 2.4 V
V
IL
SHDN Input Low Voltage ● 0.8 0.8 V
I
IN
SHDN Input Current ● ±0.01 ±1 ±0.01 ±1 µA
gm
V
Error Amplifier Transconductance 650 650 µMho
gm
I
I
LIM
Amplifier Transconductance (Note 6) 1300 1300 µMho
I
IMAX
I
MAX
Sink Current V
IMAX
= V
CC
● 8 12 16 8 12 17 µA
I
SS
Soft Start Source Current V
SS
= 0V ● –8 –12 –16 –8 –12 –17 µA
t
r
, t
f
Driver Rise/Fall Time P
VCC1
= P
VCC2
= 5V (Note 7) 80 250 80 250 ns
t
NOV
Driver Non-Overlap Time P
VCC1
= P
VCC2
= 5V 25 130 250 25 130 250 ns
DC
MAX
Maximum Duty Cycle V
COMP
= V
CC
90.5 93 90.5 93 %
Supply Voltage
V
IN
...........................................................................................
6V
V
CC
...........................................................................................
9V
P
VCC1, 2
................................................................................
13V
Input Voltage
I
FB
.......................................................................
–0.3V to 18V
C
+
, C
–
................................................
–0.3V to (V
IN
+ 0.3V)
All Other Inputs ....................... –0.3V to (V
CC
+ 0.3V)
Operating Temperature Range
LTC1649C ............................................... 0°C to 70°C
LTC1649I............................................ –40°C to 85°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ABSOLUTE MAXIMUM RATINGS
W
WW
U
T
JMAX
= 150°C, θ
JA
= 110°C/W
ORDER PART
NUMBER
LTC1649CS
LTC1649IS
TOP VIEW
S PACKAGE
16-LEAD PLASTIC SO
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
G1
P
VCC1
GND
FB
SHDN
SS
V
IN
C
–
G2
P
VCC2
V
CC
I
FB
I
MAX
COMP
CP
OUT
C
+
PACKAGE/ORDER INFORMATION
UUW
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.3V (Note 2)
(Note 1)
Consult factory for parts specified with wider operating temperature ranges.
3
LTC1649
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a part may be impaired.
Note 2: All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to ground unless otherwise
specified.
Note 3: Maximum Duty Cycle limitations will limit the output voltage
obtainable at very low supply voltages.
Note 4: Supply current at P
VCC1
and P
VCC2
is dominated by the current
needed to charge and discharge the external MOSFET gates. This current
will vary with the operating voltage and the external MOSFETs used.
Note 5: Under normal operating conditions, the charge pump will skip
cycles to maintain regulation and the apparent frequency will be lower than
700kHz.
Note 6: The I
LIM
amplifier can sink but not source current. Under normal
(not current limited) operation, the I
LIM
output current will be zero.
Note 7: Driver rise and fall times are measured from 10% to 90%.
TYPICAL PERFOR A CE CHARACTERISTICS
UW
TEMPERATURE (°C)
–40
210
220
240
20 60
1649 G02
200
190
–20 0
40 80 100
180
170
230
OSCILLATOR FREQUENCY (kHz)
V
CC
= 5V
Oscillator Frequency
vs Temperature
TEMPERATURE (°C)
–40
12.5
13.0
14.0
20 60
1649 G01
12.0
11.5
–20 0
40 80 100
11.0
10.5
13.5
I
MAX
CURRENT (µA)
V
CC
= 5V
I
MAX
Pin Current vs Temperature
TEMPERATURE (°C)
–40
70
DUTY CYCLE (%)
75
85
90
95
0
40
60
1649 G03
80
–20 20
80
100
100
V
COMP
= V
CC
V
FB
= 1.265V
V
CC
= 5V
Maximum Duty Cycle
vs Temperature
Error Amplifier Transconductance
vs Temperature
TEMPERATURE (°C)
–40
350
TRANSCONDUCTANCE (µmho)
400
500
550
600
850
700
0
40
60 100
1649 G04
450
750
800
650
–20 20
80
g
m
=
∆I
COMP
∆V
FB
V
CC
= 5V
Output Voltage vs Load Current
with Current Limit
LOAD CURRENT (A)
0
OUTPUT VOLTAGE (V)
1.5
2.0
2.5
6
10
1649 G07
1.0
0.5
0
24 8
3.0
3.5
4.0
12
T
A
= 25°C
V
CC
= 5V
FIGURE 1
R
IMAX
= 16k R
IMAX
= 33k
Load Regulation
LOAD CURRENT (A)
0
–1.0
∆V
OUT
(mV)
–0.8
–0.4
–0.2
0
0.4
1
5
7
1649 G06
–0.6
0.2
4
9
10
2
3
68
T
A
= 25°C
V
OUT
= 3.3V
V
CC
= 5V
FIGURE 1
ELECTRICAL CHARACTERISTICS
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16

LTC1649CS

Mfr. #:
Buy LTC1649CS
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators LTC1649 - 3.3V Input High Power Step-Down Switching Regulator Controller
Lifecycle:
New from this manufacturer.
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