LT3570
14
3570fb
APPLICATIONS INFORMATION
Boost Diode Selection
A Schottky diode is recommended for use with the LT3570
inverter/boost regulator. The Microsemi UPS120 is a very
good choice. Where the input to output voltage differen-
tial exceeds 20V, use the UPS140 (a 40V diode). These
diodes are rated to handle an average forward current of
1A. For applications where the average forward current
of the diode is less than 0.5A, use an ON Semiconductor
MBR0520L diode.
BOOST Pin Considerations
The capacitor and diode tied to the BOOST pin generate
a voltage that is higher than the input voltage. In most
cases, a 0.1糉 capacitor and fast switching diode (such
as the CMDSH-3 or MMSD914LT1) will work well. Fig-
ure 2 shows three ways to arrange the boost circuit. The
BOOST pin must be more than 2.5V above the SW pin for
full ef ciency. For outputs of 3.3V and higher, the standard
circuit (Figure 2a) is best. For outputs between 2.8V and
3.3V, use a small Schottky diode (such as the BAT-54).
For lower output voltages, the boost diode can be tied
to the input (Figure 2b). The circuit in Figure 2a is more
ef cient because the BOOST pin current comes from a
lower voltage source. Finally, as shown in Figure 2c, the
anode of the boost diode can be tied to another source
that is at least 3V. For example, if you are generating 3.3V
and 1.8V and the 3.3V is on whenever the 1.8V is on, the
1.8V boost diode can be connected to the 3.3V output. In
any case, be sure that the maximum voltage at the BOOST
pin is less than 60V and the voltage difference between
the BOOST and SW2 pins is less than 25V.
The minimum operating voltage of an LT3570 application
is limited by the undervoltage lockout (2.5V) and by the
maximum duty cycle. The boost circuit also limits the
minimum input voltage for proper start-up. If the input
voltage ramps slowly, or the LT3570 turns on when the
output is already in regulation, the boost capacitor may
not be fully charged. Because the boost capacitor charges
with the energy stored in the inductor, the circuit will rely
on some minimum load current to get the boost circuit
running properly. This minimum load will depend on input
and output voltages, and on the arrangement of the boost
circuit. The minimum load current generally goes to zero
once the circuit has started. Even without an output load
current, in many cases the discharged output capacitor will
present a load to the switcher that will allow it to start.
Switcher Frequency Compensation
The LT3570 uses current mode control to regulate the
output. This simpli es loop compensation. In particular, the
LT3570 does not depend on the ESR of the output capaci-
tor for stability so you are free to use ceramic capacitors
to achieve low output ripple and small circuit size.
To compensate the feedback loop of the LT3570, a series
resistor-capacitor network should be connected from
the V
C
pin to GND. For most applications, a capacitor in
the range of 500pF to 4.7nF will suf ce. A good starting
value for the compensation capacitor, C
C
, is 1nF. The
V
IN
BOOST
GND
SW
LT3570
(2a)
D3
C3
D2
C2
V
IN
BOOST
GND
SW
LT3570
(2b)
D3
C5
D2
C2
D3
V
IN
BOOST
GND
SW
LT3570
2c
C5
D2
C2
V
EXT
3570 F02
Figure 2. Boost Pin Con gurations
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
LT3645HMSE#TRPBF
IC REG DL BUCK/LINEAR 12-MSOP
LT3694IFE-1#TRPBF
IC REG TRPL BUCK/LINEAR 20TSSOP
LT4220IGN#TR
IC CTLR HOTSWAP DUAL 16-SSOP
LT4250LCN8
IC CONTRLR HOT SWAP NEG 48V 8DIP
LT4254CGN
IC CTRLR HOTSWAP POSVOLT 16SSOP
LT4256-1IS8#TRPBF
IC CTRLR HOTSWAP HV LATCH 8SOIC
LTC1392IS8#TRPBF
IC DATA ACQ SYSTEM 10BIT 8-SOIC
LTC1421ISW-2.5#PBF
IC CONTROLLER HOT SWAP 24-SOIC
相关代理商/技术参数
LT3570IFE-PBF
制造商:LINER 制造商全称:Linear Technology 功能描述:1.5A Buck Converter, 1.5A Boost Converter and LDO Controller
LT3570IFE-TRPBF
制造商:LINER 制造商全称:Linear Technology 功能描述:1.5A Buck Converter, 1.5A Boost Converter and LDO Controller
LT3570IUF#PBF
功能描述:IC REG TRPL BCK/BST/LINEAR 24QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 + 切换式 系列:- 标准包装:2,500 系列:- 拓扑:降压（降压）同步（3），线性（LDO）（2） 功能:任何功能 输出数:5 频率 - 开关:300kHz 电压/电流 - 输出 1:控制器 电压/电流 - 输出 2:控制器 电压/电流 - 输出 3:控制器 带 LED 驱动器:无 带监控器:无 带序列发生器:是 电源电压:5.6 V ~ 24 V 工作温度:-40°C ~ 85°C 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:*
LT3570IUF#TRPBF
功能描述:IC REG TRPL BCK/BST/LINEAR 24QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 + 切换式 系列:- 标准包装:2,500 系列:- 拓扑:降压（降压）同步（3），线性（LDO）（2） 功能:任何功能 输出数:5 频率 - 开关:300kHz 电压/电流 - 输出 1:控制器 电压/电流 - 输出 2:控制器 电压/电流 - 输出 3:控制器 带 LED 驱动器:无 带监控器:无 带序列发生器:是 电源电压:5.6 V ~ 24 V 工作温度:-40°C ~ 85°C 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:*
LT3570IUF-PBF
制造商:LINER 制造商全称:Linear Technology 功能描述:1.5A Buck Converter, 1.5A Boost Converter and LDO Controller
LT3570IUF-TRPBF
制造商:LINER 制造商全称:Linear Technology 功能描述:1.5A Buck Converter, 1.5A Boost Converter and LDO Controller
LT3571EUD#PBF
功能描述:IC REG BOOST ADJ 0.47A 16QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2
LT3571EUD#TRPBF
功能描述:IC REG BOOST ADJ 0.47A 16QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘