参数资料
| 型号： | LTC3813EG#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM CM 28-SSOP |
| 标准包装： | 47 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 1MHz |
| 电源电压： | 7 V ~ 75 V |
| 降压： | 无 |
| 升压： | 是 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 28-SSOP（0.209"，5.30mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1336 (CN2011-ZH PDF) |
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LTC3813
OPERATION
Main Control Loop
The LTC3813 is a current mode controller for DC/DC step-
up converters. In normal operation, the top MOSFET is
turned on for a ?xed interval determined by a one-shot
timer (OST). When the top MOSFET is turned off, the bot-
tom MOSFET is turned on until the current comparator
I CMP trips, restarting the one-shot timer and initiating the
next cycle. Inductor current is determined by sensing the
voltage between the SENSE – and SENSE + pins using a
sense resistor or the bottom MOSFET on-resistance. The
voltage on the I TH pin sets the comparator threshold cor-
responding to the inductor peak current. The fast 25MHz
error ampli?er EA adjusts this voltage by comparing the
feedback signal V FB to the internal 0.8V reference volt-
age. If the load current increases, it causes a drop in the
feedback voltage relative to the reference. The I TH voltage
then rises until the average inductor current again matches
the load current.
The operating frequency is determined implicitly by the
top MOSFET on-time (t OFF ) and the duty cycle required to
maintain regulation. The one-shot timer generates a top
MOSFET on-time that is inversely proportional to the I OFF
current and proportional to the V OFF voltage. Connecting
V OUT to I OFF and V IN to V OFF with a resistive divider keeps
the frequency approximately constant with changes in V IN .
The nominal frequency can be adjusted with an external
resistor R OFF .
For applications with stringent constant-frequency require-
ments, the LTC3813 can be synchronized with an external
clock. By programming the nominal frequency the same as
the external clock frequency, the LTC3813 behaves as a con-
inductor current will never exceed the value programmed
on the V RNG pin.
Overvoltage and undervoltage comparators OV and UV
pull the PGOOD output low if the output feedback voltage
exits a ±10% window around the regulation point after the
internal 125μs power bad mask timer expires. Furthermore,
in an overvoltage condition, M1 is turned off and M2 is
turned on immediately and held on until the overvoltage
condition clears.
The LTC3813 provides two undervoltage lockout com-
parators—one for the INTV CC /DRV CC supply and one for
the input supply V IN . The INTV CC UV threshold is 6.2V to
guarantee that the MOSFETs have suf?cient gate drive volt-
age before turning on. The V IN UV threshold (UVIN pin) is
0.8V with 10% hysteresis which allows programming the
V IN threshold with the appropriate resistor divider con-
nected to V IN . If either comparator inputs are under the
UV threshold, the LTC3813 is shut down and the drivers
are turned off.
Strong Gate Drivers
The LTC3813 contains very low impedance drivers capable
of supplying amps of current to slew large MOSFET gates
quickly. This minimizes transition losses and allows paral-
leling MOSFETs for higher current applications. A 100V
?oating high side driver drives the top side MOSFET and
a low side driver drives the bottom side MOSFET (see
Figure 1). The bottom side driver is supplied directly
from the DRV CC pin. The top MOSFET drivers are biased
from ?oating bootstrap capacitor C B , which normally is
recharged during each off cycle through an external diode
stant-frequency part against the load and supply variations.
Pulling the SHDN pin low forces the controller into its
shutdown state, turning off both M1 and M2. Forcing a
voltage above 1.5V will turn on the device.
LTC3813
DRV CC
DRV CC
BOOST
TG
D B
C B
V IN
L
+
C IN
Fault Monitoring/Protection
SW
Constant off-time current mode architecture provides
accurate cycle-by-cycle current limit protection—a fea-
ture that is very important for protecting the high volt-
BGRTN
BG
M2
M1
+
3813 F01
V OUT
C OUT
age power supply from output overcurrent conditions.
The cycle-by-cycle current monitor guarantees that the
0V TO –5V
Figure 1. Floating TG Driver Supply and Negative BG Return
3813fb
11
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| LTC3813IG#PBF | 功能描述:IC REG CTRLR BST PWM CM 28-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
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