step-down DC/DC controller providing excellent AC and
DC load and line regulation. The device incorporates an
accurate undervoltage lockout feature that shuts down the
LTC1772B when the input voltage falls below 2.0V.
The LTC1772B provides a ± 2.5% output voltage accuracy
and consumes only 270μA of quiescent current. In shut-
down, the device draws a mere 8μA.
To further maximize the life of a battery source, the
external P-channel MOSFET is turned on continuously
in dropout (100% duty cycle). High constant operating
frequency of 550kHz allows the use of a small external
inductor.
The LTC1772B is available in a small footprint 6-lead
TSOT-23.
For a Burst Mode operation enabled version of the
LTC1772B, please refer to the LTC1772 data sheet.
L,
LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Burst Mode
®
Operation Disabled for Lower Output
Ripple at Light Loads
High Efficiency: Up to 94%
High Output Currents Easily Achieved
Wide V
IN
Range: 2.5V to 9.8V
Constant Frequency 550kHz Operation
Low Dropout: 100% Duty Cycle
Output Voltage Down to 0.8V
Current Mode Operation for Excellent Line and Load
Transient Response
Shutdown Mode Draws Only 8µA Supply Current
Tiny 6-Lead TSOT-23 Package
APPLICATIONS
n
n
n
n
n
One or Two Lithium-Ion-Powered Applications
Cellular Telephones
Wireless Devices
Portable Computers
Distributed 3.3V, 2.5V or 1.8V Power Systems
TYPICAL APPLICATION
R1
0.03Ω
1
10k
220pF
I
TH
/RUN PGATE
LTC1772B
2
3
GND
V
FB
V
IN
SENSE
–
5
4
D1
6
L1
M1 4.7μH
C1
10μF
10V
V
IN
2.5V
TO 9.8V
100
95
90
EFFICIENCY (%)
V
OUT
2.5V
2A
174k
85
80
75
70
C1: TAIYO YUDEN LMK325BJ106K-T
C2A: SANYO 6TPA47M
C2B: AVX 0805ZC105KAT1A
D1: MOTOROLA MBRM120T3
L1: MURATA LQN6C-4R7
M1: FAIRCHILD FDC638P
R1: IRC LRC-LR1206-01-R030F
80.6k
65
60
1772 F01a
Efficiency vs Load Current*
LTC1772
Burst Mode
OPERATION
+
C2A
47μF
6V
C2B
1μF
10V
LTC1772B
NON-Burst Mode
OPERATION
V
IN
= 3.6V
V
OUT
= 2.5V
10
100
1000
10000
LOAD CURRENT (mA)
*OUTPUT RIPPLE WAVEFORMS FOR THE CIRCUIT
OF FIGURE 1 APPEAR IN FIGURE 2.
1772 F01b
Figure 1. High Efficiency, High Output Current 2.5V/2A Regulator
1772bfa
1
LTC1772B
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
I
TH
/RUN 1
GND 2
V
FB
3
6 PGATE
5 V
IN
4 SENSE
–
Input Supply Voltage (V
IN
) .........................– 0.3V to 10V
SENSE
–
, PGATE Voltages ...............–0.3V to (V
IN
+ 0.3V)
V
FB
, I
TH
/RUN Voltages............................... –0.3V to 2.4V
PGATE Peak Output Current (< 10µs) ........................ 1A
Storage Ambient Temperature Range.....– 65°C to 150°C
Operating Temperature Range (Note 2).... –40°C to 85°C
Junction Temperature (Note 3) ............................ 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
T
JMAX
= 150°C,
θ
JA
= 230°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC1772BES6#PBF
LTC1772BIS6#PBF
LEAD BASED FINISH
LTC1772BES6
LTC1772BIS6
TAPE AND REEL
LTC1772BES6#TRPBF
LTC1772BIS6#TRPBF
TAPE AND REEL
LTC1772BES6#TR
LTC1772BIS6#TR
PART MARKING*
LTVU
LTVU
PART MARKING*
LTVU
LTVU
PACKAGE DESCRIPTION
6-Lead Plastic TSOT Package
6-Lead Plastic TSOT Package
PACKAGE DESCRIPTION
6-Lead Plastic TSOT Package
6-Lead Plastic TSOT Package
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS
PARAMETER
Input DC Supply Current
Normal Operation
Shutdown
UVLO
Undervoltage Lockout Threshold
Shutdown Threshold (at I
TH
/RUN)
Start-Up Current Source
Regulated Feedback Voltage
Output Voltage Line Regulation
Output Voltage Load Regulation
V
ITH
/RUN = 0V
0°C to 70°C (Note 5)
–40°C to 85°C (Note 5)
2.4V ≤ V
IN
≤ 9.8V (Note 5)
CONDITIONS
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 4.2V unless otherwise specified. (Note 2)
MIN
TYP
270
8
6
l
l
l
l
MAX
420
22
10
2.35
2.40
0.55
0.85
0.820
0.830
UNITS
μA
μA
μA
V
V
V
μA
V
V
mV/V
mV/μA
mV/μA
Typicals at V
IN
= 4.2V (Note 4)
2.4V ≤ V
IN
≤ 9.8V, PGATE Logic High
2.4V ≤ V
IN
≤ 9.8V, V
ITH
/RUN = 0V
V
IN
< UVLO Threshold
V
IN
Falling
V
IN
Rising
1.55
1.85
0.15
0.25
0.780
0.770
2.00
2.10
0.35
0.5
0.800
0.800
0.05
2.5
2.5
I
TH
/RUN Sinking 5μA (Note 5)
I
TH
/RUN Sourcing 5μA (Note 5)
1772bfa
2
LTC1772B
ELECTRICAL CHARACTERISTICS
PARAMETER
V
FB
Input Current
Overvoltage Protect Threshold
Overvoltage Protect Hysteresis
Oscillator Frequency
Gate Drive Rise Time
Gate Drive Fall Time
Peak Current Sense Voltage
V
FB
= 0.8V
V
FB
= 0V
C
LOAD
= 3000pF
C
LOAD
= 3000pF
(Note 6)
500
CONDITIONS
(Note 5)
Measured at V
FB
0.820
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 4.2V unless otherwise specified. (Note 2)
MIN
TYP
10
0.860
20
550
120
40
40
105
650
MAX
50
0.895
UNITS
nA
V
mV
kHz
kHz
ns
ns
mV
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
The LTC1772BE is guaranteed to meet specifications from 0°C to
85°C. Specifications over the –40°C to 85°C operating temperature range
are assured by design, characterization and correlation with statistical
process controls. The LTC1772BI is guaranteed to meet specifications over
the full –40°C to 85°C operating temperature range.
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
•
θ
JA
°C/W)
Note 4:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 5:
The LTC1772B is tested in a feedback loop that servos V
FB
to the
output of the error amplifier.
Note 6:
Peak current sense voltage is reduced dependent on duty cycle to
a percentage of value as given in Figure 2.
1772bfa
3
LTC1772B
TYPICAL PERFORMANCE CHARACTERISTICS
Reference Voltage
vs Temperature
825
820
815
V
FB
VOLTAGE (mV)
Normalized Oscillator Frequency
vs Temperature
10
8
NORMALIZED FREQUENCY (%)
Undervoltage Lockout Trip
Voltage vs Temperature
2.24
2.20
2.16
TRIP VOLTAGE (V)
V
IN
= 4.2V
V
IN
= 4.2V
V
IN
FALLING
6
4
2
0
–2
–4
–6
–8
810
805
800
795
790
785
780
775
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1772 G01
2.12
2.08
2.04
2.00
1.96
1.92
1.88
–10
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1772 G02
1.84
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1772 G03
Maximum (V
IN
– SENSE
–
) Voltage
vs Duty Cycle
120
110
TRIP VOLTAGE (mV)
Shutdown Threshold
vs Temperature
600
560
520
I
TH
/RUN VOLTAGE (mV)
V
IN
= 4.2V
T
A
= 25°C
V
IN
= 4.2V
100
90
80
70
60
50
40
20
30
40
50 60 70 80
DUTY CYCLE (%)
90
100
480
440
400
360
320
280
240
200
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1772 G05
1772 G04
1772bfa
4
LTC1772B
PIN FUNCTIONS
I
TH
/RUN (Pin 1):
This pin performs two functions. It
serves as the error amplifier compensation point as well
as the run control input. Nominal voltage range for this
pin is 0.85V to 1.9V. Forcing this pin below 0.35V causes
the device to be shut down. In shutdown all functions are
京公网安备 11010802033920号
EEWORLD
