allows the efficiency to be optimized while minimizing
the solution footprint. Both converters feature soft-start
and current limit protection. The uncommitted gain block
can be configured as an LDO or utilized as a battery-good
comparator.
The buck converter is current mode controlled with internal
synchronous rectification to improve efficiency. Pin-select-
able Burst Mode operation can be enabled to improve light
load efficiency, or the buck converter can be operated in
low noise PWM mode for sensitive applications.
The buck-boost converter provides continuous conduc-
tion operation to maximize efficiency and minimize noise.
At light loads, use of Burst Mode operation will improve
efficiency.
The LTC3520 provides a <1μA shutdown mode and over-
temperature shutdown on both converters. The LTC3520
is available in a low profile (0.75mm) 24-lead 4mm
×
4mm QFN package.
n
n
n
n
n
n
n
n
Dual High Efficiency DC/DC Converters:
Buck-Boost (V
OUT
: 2.2V to 5.25V, I
OUT
= 1A at
V
OUT
= 3.3V, V
IN
≥ 3V)
Buck (V
OUT
: 0.8V to V
IN
, I
OUT
= 600mA)
2.2V to 5.5V Input Voltage Range
Pin-Selectable Burst Mode
®
Operation
Uncommitted Gain Block for LDO Controller, Battery
Good Indication or Sequencing
Programmable 100kHz to 2MHz Switching Frequency
55μA Total Quiescent Current for Both Converters in
Burst Mode Operation
Thermal and Overcurrent Protection
<1μA Quiescent Current in Shutdown
24-Lead 4mm
×
4mm QFN Package
APPLICATIONS
n
n
n
n
Portable Media Players
Digital Cameras
Handheld PCs, PDAs
GPS Receivers
L,
LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners. Protected by U.S. Patents, including 5481178, 6166527, 6304066, 6404251, 6580258.
TYPICAL APPLICATION
3.3V at 500mA, 1.8V at 600mA and 1.5V at 200mA Converter
V
IN
2.2V TO
5.5V
V
OUT2
1.8V
600mA
Efficiency vs V
IN
100
BUCK-BOOST
I
OUT
= 150mA
BUCK
I
OUT
= 250mA
22μF
4.7μH
255k
PV
IN1
PV
IN2
PV
IN3
SV
IN
SW1A
SW1B
V
OUT1
SW2
V
C1
FB2
200k
0.01μF
SS2
54.9k
R
T
PWM1
BURST PWM
PWM2
SD3
OFF ON
SD2
SD1
PGND1 SGND PGND2
A
IN
A
OUT
LTC3520
FB1
4.7μH
V
OUT1
3.3V
500mA
1A FOR
V
IN
≥ 3V
95
EFFICIENCY (%)
90
85
80
75
70
2.2
470pF
56pF
1M
15k
0.01μF
10k
309k
47μF
10μF
27pF
SS1
V
OUT2
V
OUT
1.5V
200mA
4.7μF
33pF
100k
2.7
3.2
110k
3520 TA01
4.2
3.7
V
IN
(V)
4.7
5.2
3520 TA01b
3520fa
1
LTC3520
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
PGND1
V
OUT1
18 FB1
17 SS1
25
16 SGND
15 V
C1
14 FB2
13 SS2
7
SD2
8
SD3
9 10 11 12
PGND2
PV
IN2
SW2
PWM2
SW1A
SW1B
PV
IN3
SV
IN
1
A
OUT
2
A
IN
3
R
T
4
PWM1 5
SD1
6
PV
IN1
PV
IN1
, PV
IN2
, PV
IN3
, SV
IN
Voltage................ –0.3V to 6V
SW1A, SW1B, SW2 Voltage
DC............................................................ –0.3V to 6V
Pulsed <100ns ............................................ –1V to 7V
Voltage, All Other Pins ................................. –0.3V to 6V
Operating Junction Temperature Range
(Note 2).................................................. –40°C to 125°C
Maximum Junction Temperature (Note 5) ............ 125°C
Storage Temperature Range .................. –65°C to 150°C
24 23 22 21 20 19
UF PACKAGE
24-LEAD (4mm 4mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 37°C/W
EXPOSED PAD (PIN 25) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3520EUF#PBF
LTC3520IUF#PBF
TAPE AND REEL
LTC3520EUF#TRPBF
LTC3520IUF#TRPBF
PART MARKING*
3520
3520
PACKAGE DESCRIPTION
24-Lead (4mm
×
4mm) Plastic QFN
24-Lead (4mm
×
4mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C, S
VIN
= P
VIN1
= P
VIN2
= P
VIN3
= 3.6V, V
OUT1
= 3.3V, R
T
= 54.9k,
unless otherwise noted.
PARAMETER
Input Voltage
Quiescent Current in Shutdown
V
SD1
= V
SD2
= V
SD3
= 0V
LTC3520E
LTC3520I
SV
IN
Rising
V
FB1
= V
FB2
= 0.88V, V
SD3
= 0V
R
T
= 54.9k
l
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
l
l
l
TYP
MAX
5.5
UNITS
V
μA
μA
V
μA
MHz
Ω
Ω
2.2
0.01
0.5
2
55
0.8
1
0.32
0.18
1
4
2.2
1.2
Undervoltage Lockout
Burst Mode Quiescent Current, Both Converters
Oscillator Frequency
Buck Converter
PMOS Switch Resistance
NMOS Switch Resistance
NMOS Switch Leakage
PMOS Switch Leakage
V
SW2
= 5V, S
VIN
= P
VIN1
= P
VIN2
= P
VIN3
= 5V
V
SW2
= 0V, S
VIN
= P
VIN1
= P
VIN2
= P
VIN3
= 5V
0.1
0.1
5
10
μA
μA
3520fa
2
LTC3520
ELECTRICAL CHARACTERISTICS
PARAMETER
Feedback Voltage (FB2 Pin)
Feedback Input Current (FB2 Pin)
PMOS Current Limit
Maximum Duty Cycle
Minimum Duty Cycle
Soft-Start Charging Current
SD2
Input High Voltage
SD2
Input Low Voltage
SD2
Input Current
Buck-Boost Converter
Output Voltage
PMOS Switch Resistance
NMOS Switch Resistance
NMOS Switch Leakage
PMOS Switch Leakage
Feedback Voltage (FB1 Pin)
Feedback Input Current (FB1 Pin)
Forward Current Limit
(Note 3)
LTC3520E
LTC3520I
(Note 3)
(Note 3)
l
l
l
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C, S
VIN
= P
VIN1
= P
VIN2
= P
VIN3
= 3.6V, V
OUT1
= 3.3V, R
T
= 54.9k,
unless otherwise noted.
CONDITIONS
(Note 4)
(Note 3)
V
FB2
= 0.72V
V
FB2
= 0.88V
l
l
l
l
MIN
0.771
0.8
100
TYP
0.790
1
1.25
MAX
0.809
50
UNITS
V
nA
A
%
0
6
1.4
0.4
0.01
2.2
0.20
0.15
1
5.25
%
μA
V
V
μA
V
Ω
Ω
V
SW1A
= V
SW1B
= 5V, S
VIN
= P
VIN1
= P
VIN2
= P
VIN3
= 5V
V
SW1A
= V
SW1B
= 0V, S
VIN
= P
VIN1
= P
VIN2
= P
VIN3
= 5V
l
0.1
0.1
0.766
0.782
1
1.4
1.25
2
1.85
560
325
80
500
14
5
10
0.798
50
μA
μA
V
nA
A
A
mA
mA
dB
μA
μA
%
%
Reverse Current Limit
Burst Mode Operation Current Limit
Error Amplifier Gain
Error Amplifier Sink Current
Error Amplifier Source Current
Maximum Duty Cycle
Minimum Duty Cycle
Soft-Start Charging Current
SD1,
PWM1 Input High Voltage
SD1,
PWM1 Input Low Voltage
SD1,
PWM1 Input Current
Gain Block
Quiescent Current
A
IN
Pin Threshold Voltage
A
IN
Pin Input Bias Current
A
OUT
Sink Current
A
OUT
Source Current
A
OUT
Pin Voltage
Open Loop Gain
Boost (% Switch C is On)
Buck (% Switch A is On)
l
l
70
100
80
0
6
%
μA
V
1.4
0.4
0.01
V
AIN
= 0.88V, V
SD1
= V
SD2
= 0V
l
V
μA
μA
1
45
0.770
0.786
1
17
18
25
80
150
0.802
50
V
nA
mA
μA
mV
dB
V
AIN
= 0.72V, V
AOUT
= 1.8V
V
AIN
= 0.88V, V
AOUT
= 1.8V
V
AIN
= 0.72V, I
AOUT
= 1mA
3520fa
3
LTC3520
ELECTRICAL CHARACTERISTICS
PARAMETER
Propagation Delay
SD3
Input High Voltage
SD3
Input Low Voltage
SD3
Input Current
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 LTC3520E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3520I is guaranteed
to meet performance specifications over the full –40°C to 125°C operating
junction temperature range.
0.01
CONDITIONS
A
OUT
Falling
1.4
0.4
1
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C, V
IN
= 3.6V, V
OUT1
= 3.3V, V
OUT2
= 1.8V, R
T
= 54.9k, unless
otherwise noted.
MIN
TYP
11
MAX
UNITS
μs
V
V
μA
Note 3:
Current measurements are performed when the LTC3520 is not
switching. The current limit values in operation will be somewhat higher
due to the propagation delay of the comparators.
Note 4:
The LTC3520 is tested in a proprietary non-switching test mode
that internally connects the FB2 pin to the output of the buck converter
error amplifier.
Note 5:
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
便携式医疗设备的特殊性决定了它们应该是对用户友好的、必须工作在无菌环境下，并且空间占用小、耗能低。 同时，便携式医疗设备还需要足够的计算能力以便处理医疗数据，能够连接到无线或有线接口以便记录和发送数据。从设计人员的角度考虑，上述需求需要低功耗的单片机（MCU）和数字信号控制器（Digital Signal Controller，DSC）。 正是有了嵌入式处理器，设计人员才有可能设...[详细]
微控制器 MCU
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
