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| 型号： | LTC3458EDE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BOOST SYNC ADJ 1.4A 12DFN |
| 标准包装： | 2,500 |
| 类型： | 升压（升压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 2 V ~ 7.5 V |
| 输入电压： | 1.5 V ~ 6 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 1.5MHz |
| 电流 - 输出： | 1.4A |
| 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： | 12-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 12-DFN（4x3） |
LTC3458
APPLICATIO S I FOR ATIO
C BURST =
PMOS
transition occurs using a single resistor. During Burst
Mode operation, the oscillator is shut down, since the on
time is determined by the time it takes the inductor current
to reach a fixed peak current, and the off time is deter-
mined by the time it takes for the inductor current to return
to zero.
In Burst Mode operation, the IC delivers energy to the
output until it is regulated and then goes into a sleep mode
where the outputs are off and the IC is consuming only
15 μ A of quiescent current. In this mode the output ripple
voltage has a variable frequency component with load
current and will be typically 2% peak-to-peak. This maxi-
mizes efficiency at very light loads by minimizing switch-
ing and quiescent losses. Burst Mode ripple can be re-
duced slightly by using more output capacitance (22 μ F or
greater). This capacitor does not need to be a low ESR type
if low ESR ceramics are also used. Another method of
reducing Burst Mode ripple is to place a small feed-
forward capacitor across the upper resistor in the V OUT
feedback divider network.
During Burst Mode operation, COMP is disconnected
from the error amplifier in an effort to hold the voltage on
the external compensation network where it was before
entering Burst Mode operation. To minimize the effects of
leakage current and stray resistance, voltage clamps limit
the minimum and maximum voltage on COMP during
Burst Mode operation. This minimizes the transient expe-
rienced when a heavy load is suddenly applied to the
converter after being in Burst Mode operation for an
extended period of time.
For automatic operation, an RC network should be con-
nected from BURST to ground. The value of the resistor
will control the average load current (I BURST ) at which
Burst Mode operation will be entered and exited (there is
hysteresis to prevent oscillation between modes). The
equation given for the capacitor on BURST is for the
minimum value, to prevent ripple on the BURST pin from
causing the part to oscillate in and out of Burst Mode
operation at the current where the mode transition occurs.
C OUT ? V OUT
10 , 000
where C BURST(MIN) and C OUT are in μ F.
Note: the BURST pin only sources current based on
current delivered to V OUT through the P-channel MOSFET.
If current in the inductor is allowed to go negative (this can
occur at very light loads and high step-up ratios), the burst
threshold may become inaccurate, preventing the IC from
entering Burst Mode operation. For R BURST values greater
than 200k, a larger than recommended inductor value may
be needed to ensure positive inductor current and auto-
matic Burst Mode operation.
In the event that a sudden load transient causes the voltage
level on FB to drop by more than 4% from the regulation
value, an internal pull-up is applied to BURST, forcing the
part quickly out of Burst Mode operation. For optimum
transient response when going between Burst Mode op-
eration and PWM mode, Burst can be controlled manually
by the host. This way PWM mode can be commanded
before the load step occurs, minimizing output voltage
drop. Note that Burst Mode operation is inhibited during
start-up and soft-start.
Manual Control
For applications requiring fixed frequency operation at all
load currents, connect the BURST pin to V OUT through a
50k Ω resistor. To force Burst Mode operation, ground the
BURST pin.
For applications where a large load step can be anticipated,
the circuit below can be used to reduce the voltage
transient on V OUT . Automatic operation is achieved when
the external PMOS is off and fixed frequency operation is
commanded when the external PMOS is on. In shutdown,
the PMOS should be off.
V IN
HIGH: AUTO MODE
LOW: FIXED FREQUENCY
BURST
R BURST =
10
I BURST
133k
0.01 μ F
where R BURST is in k Ω and I BURST is in amps.
Figure 1
3458 FO2
3458fa
10
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相关代理商/技术参数 |
参数描述 |
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| LTC3458L | 制造商:LINER 制造商全称:Linear Technology 功能描述:1.7A, 1.5MHz Synchronous Step-Up DC/DC Converter with Output Disconnect |
| LTC3458LEDE | 功能描述:IC REG BOOST SYNC ADJ 1.4A 12DFN RoHS:否 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 |
| LTC3458LEDE#PBF | 功能描述:IC REG BOOST SYNC ADJ 1.4A 12DFN 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 |
| LTC3458LEDE#TRPBF | 功能描述:IC REG BOOST SYNC ADJ 1.4A 12DFN 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 |
| LTC3459 | 制造商:LINER 制造商全称:Linear Technology 功能描述:1.2MHz Step-Up DC/DC Converter in SOT-23 |
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