- 您现在的位置：买卖IC网 > Sheet目录868 > LTM8008HV#PBF (Linear Technology)IC DC/DC UMODULE 16-LGA
LTM8008
APPLICATIONS INFORMATION
LTM8008
( R3 + R4 )
V VIN,FALLING = 1.21 ?
RunningInputVoltageVersusStartVoltage
In normal operation the LTM8008 SEPIC Converter output
SPV is used to run the INTV CC internal biasing through
a rectifying diode (see the Block Diagram). This allows
the internal MOSFET driver Q1 and other circuitry to be
properly biased even when the input voltage falls as low
as 3V. At start-up, however, the SPV voltage is low and
INTV CC is derived from V IN through a linear regulator. In
order to properly bias the LTM8008 internal circuitry at
start-up, V IN must rise to at least 6V.
Main Control Loop
The LTM8008 uses a fixed frequency, current mode con-
trol scheme to provide excellent line and load regulation.
At the start of each oscillator cycle, a latch turns on the
internal power MOSFET switch. The switch current flows
through an internal current sensing resistor and generates
a voltage proportional to the switch current. This current
sense voltage is added to a stabilizing slope compensation
ramp and the resulting sum is compared with the voltage
on the V C pin. When the stabilized current sense voltage
exceeds the level of the V C pin, the internal latch is reset,
turning off the power switch. The level at the V C pin is an
amplified version of the difference between the feedback
voltage and the reference voltage. In this manner, the error
amplifier sets the correct peak switch current level to keep
the output in regulation. The LTM8008 is also equipped
with a switch current limit function. If the detected current
is higher than 8.2A, typical, the internal circuitry will turn
off Q1 for the rest of the switching cycle.
The LTM8008 has overvoltage protection functions to pro-
tect the converter from excessive output voltage overshoot
during start-up or recovery from a short-circuit condition.
If the output voltage exceeds the targeted set point by
8%, internal circuitry will actively inhibit switching for the
duration of an output overvoltage condition.
Programming Turn-On and Turn-Off Thresholds with
the RUN Pin
The RUN pin controls whether the LTM8008 is enabled
or shut down. Low power circuitry allows the user to ac-
curately program the supply voltage at which the SEPIC
converter turns on and off. The falling value can be ac-
curately set by the resistor divider network composed of
R3 and R4 shown in Figure 1.
V IN
R3
RUN
R4
8008 F01
Figure 1. The LTM8008 Turn-On and Turn-Off Thresholds Are Set
by a Simple Resistor Network
If RUN is above 1.21V, the LTM8008 is running. Below
1.21V and above 0.7V, the LTM8008 is off and the RUN
pin sinks a hysteresis current (typically 2μA). Below 0.7V,
the LTM8008 is not switching and is in a low power state,
drawing less than 70μA at V IN . The typical falling threshold
voltage and rising threshold voltage can be calculated by
the following equations:
R4
V VIN,RISING = 2μA ? R3 + V IN,FALLING
For applications where the RUN pin is not used, the RUN
pin can be connected directly to the input voltage INTV CC
for always-on operation.
INTV CC Regulator Bypassing and Operation
An internal, low dropout (LDO) voltage regulator produces
the INTV CC supply which powers the internal circuitry during
start-up or whenever SPV is low. The LTM8008 contains
an undervoltage lockout comparator and an overvoltage
lockout comparator for the INTV CC supply. The INTV CC
undervoltage (UV) function protects the internal circuitry
from attempting to operate in a brown-out condition, while
the overvoltage (OV) function protects the gate of the
power MOSFET and excessive power dissipation within
the LTM8008 in the case of a fault. When INTV CC is below
the UV threshold, or above the OV threshold, switching
stops and the soft-start operation will be triggered.
The INTV CC regulator must be bypassed to ground im-
mediately adjacent to the LTM8008 pins with a minimum
of a 4.7μF ceramic capacitor. Good bypassing is neces-
sary to supply the high transient currents required by the
MOSFET gate driver.
8008fa
8
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
LTM8020IV#PBF
IC DC/DC UMODULE 200MA 21-LGA
LTM8023MPV#PBF
IC BUCK SYNC ADJ 2A 50LGA
LTM8025MPV#PBF
IC CONVERTER BUCK 3A ADJ 70LGA
LTM8026MPV#PBF
IC UMODULE 36VIN 5A CVCC 81LGA
LTM8027EV#PBF
IC BUCK SYNC ADJ 4A 113LGA
LTM8032MPY#PBF
IC DC/DC UMODULE 2A 71BGA
LTM8033MPV#PBF
IC DC-DC UMODULE BUCK 3A 76-LGA
LTM8040IV#PBF
IC LED DRVR HP CONST CURR 66-LGA
相关代理商/技术参数
LTM8008HVPBF
制造商:LINER 制造商全称:Linear Technology 功能描述:72VIN, 6 Output DC/DC SEPIC μModule Regulator
LTM8020
制造商:LINER 制造商全称:Linear Technology 功能描述:Low VIN, 8A DC/DC μModule Regulator
LTM8020EV#PBF
功能描述:IC DC/DC UMODULE 200MA 21-LGA RoHS:是 类别:电源 - 板载 >> DC DC Converters 系列:µModule® 设计资源:VI-200, VI-J00 Design Guide, Appl Manual 标准包装:1 系列:* 类型:隔离 输出数:1 电压 - 输入（最小）:55V 电压 - 输入（最大）:100V Voltage - Output 1:5.8V Voltage - Output 2:- Voltage - Output 3:- 电流 - 输出（最大）:* 电源（瓦） - 制造商系列:100W 电压 - 隔离:* 特点:* 安装类型:通孔 封装/外壳:9 针半砖 BusMod 尺寸/尺寸:2.36" L x 2.28" W x 1.08" H（59.9mm x 57.9mm x 27.4mm） 包装:散装 工作温度:-25°C ~ 100°C 效率:* 电源（瓦特）- 最大:*
LTM8020EV#PBF
制造商:Linear Technology 功能描述:DC/DC Converter IC
LTM8020EVPBF
制造商:Linear Technology 功能描述:DC to DC Step Down Power Supply
LTM8020EV-PBF
制造商:LINER 制造商全称:Linear Technology 功能描述:200mA, 36V DC/DC μModule
LTM8020IV#PBF
功能描述:IC DC/DC UMODULE 200MA 21-LGA RoHS:是 类别:电源 - 板载 >> DC DC Converters 系列:µModule® 设计资源:VI-200, VI-J00 Design Guide, Appl Manual 标准包装:1 系列:* 类型:隔离 输出数:1 电压 - 输入（最小）:55V 电压 - 输入（最大）:100V Voltage - Output 1:5.8V Voltage - Output 2:- Voltage - Output 3:- 电流 - 输出（最大）:* 电源（瓦） - 制造商系列:100W 电压 - 隔离:* 特点:* 安装类型:通孔 封装/外壳:9 针半砖 BusMod 尺寸/尺寸:2.36" L x 2.28" W x 1.08" H（59.9mm x 57.9mm x 27.4mm） 包装:散装 工作温度:-25°C ~ 100°C 效率:* 电源（瓦特）- 最大:*
LTM8020IV#PBF
制造商:Linear Technology 功能描述:DC/DC Controller LTC 制造商:Linear Technology 功能描述:IC, DC/DC MOD REGULATOR, 450kHz, LGA-21