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| 型号： | MAX1993ETG+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 21/36页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 24-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 75 |
| 系列： | Quick-PWM™ |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 600kHz |
| 占空比： | 100% |
| 电源电压： | 4.5 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 ~ 85°C |
| 封装/外壳： | 24-WFQFN 裸露焊盘 |
| 包装： | 管件 |
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Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
current only at the start of the off-cycle. See Setting the
Current Limit section for various current-sense configu-
C BYP
rations (Figure 10) and LSAT recommendations.
MOSFET Gate Drivers (DH, DL)
The DH and DL drivers are optimized for driving moder-
MAX1992
MAX1993
V DD
BST
(R BST )*
D BST
ately sized high-side and larger low-side power
MOSFETs. This is consistent with the low duty factor seen
in notebook applications, where a large V IN - V OUT differ-
ential exists. An adaptive dead-time circuit monitors the
DL output and prevents the high-side MOSFET from turn-
ing on until DL is off. A similar adaptive dead-time circuit
monitors the DH output, preventing the low-side MOSFET
from turning on until DH is off. There must be a low-resis-
tance, low-inductance path from the DL and DH drivers to
the MOSFET gates in order for the adaptive dead-time
circuits to work properly; otherwise, the sense circuitry in
the MAX1992/MAX1993 interpret the MOSFET gates as
“off” while charge actually remains. Use very short, wide
V DD
DH
LX
DL
PGND
C BST
(C NL )*
N H
N L
INPUT (V IN )
L
V GS ( TH ) < V IN ? RSS ?
traces (50 mils to 100 mils wide if the MOSFET is 1in from
the driver).
The internal pulldown transistor that drives DL low is
robust, with a 0.6 Ω (typ) on-resistance. This helps prevent
DL from being pulled up because of capacitive coupling
from the drain to the gate of the low-side MOSFETs when
the inductor node (LX) quickly switches from ground to
V IN . Applications with high-input voltages and long induc-
tive driver traces can require additional gate-to-source
capacitance to ensure that fast-rising LX edges do not
pull up the low-side MOSFETs gate, causing shoot-
through currents. The capacitive coupling between LX
and DL created by the MOSFET’s gate-to-drain capaci-
tance (C RSS ), gate-to-source capacitance (C ISS - C RSS ),
and additional board parasitics should not exceed the
following minimum threshold.
? C ?
? C ISS ?
Lot-to-lot variation of the threshold voltage can cause
problems in marginal designs. Alternatively, adding a
resistor of less than 10 Ω in series with BST can remedy
the problem by increasing the turn-on time of the high-
side MOSFET without degrading the turn-off time
(Figure 6).
(R BST )* OPTIONAL—THE RESISTOR LOWERS EMI BY DECREASING
THE SWITCHING NODE RISE TIME.
(C NL )* OPTIONAL—THE CAPACITOR REDUCES LX TO DL CAPACITIVE
COUPLING THAT CAN CAUSE SHOOT-THROUGH CURRENTS.
Figure 6. Optional Gate Driver Circuitry
POR, UVLO, and Soft-Start
Power-on reset (POR) occurs when V CC rises above
approximately 2V, resetting the fault latch and soft-start
counter, powering up the reference, and preparing the
PWM for operation. Until V CC reaches 4.25V (typ), V CC
undervoltage lockout (UVLO) circuitry inhibits switch-
ing. The controller inhibits switching by pulling DH low
and holding DL low when OVP and shutdown dis-
charge are disabled or forcing DL high when OVP and
shutdown discharge are enabled (Table 6). When V CC
rises above 4.25V, the controller activates the PWM
controller and initializes soft-start.
Soft-start allows a gradual increase of the internal current-
limit level during startup to reduce the input surge cur-
rents. The MAX1992/MAX1993 divide the soft-start period
into five phases. During the first phase, the controller lim-
its the current limit to only 20% of the full current limit. If
the output does not reach regulation within 425μs, soft-
start enters the second phase, and the current limit is
increased by another 20%. This process repeats until the
maximum current limit is reached after 1.7ms or when the
output reaches the nominal regulation voltage, whichever
occurs first (see soft-start waveforms in the Typical
Operating Characteristics ). Adding a capacitor in parallel
with the external ILIM resistors creates a continuously
adjustable analog soft-start function.
______________________________________________________________________________________
21
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1993ETG+ | 功能描述:电压模式 PWM 控制器 Step-Down w/Inductor RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| MAX1993ETG+T | 功能描述:电压模式 PWM 控制器 Step-Down w/Inductor RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| MAX1993ETG+TG40 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1993ETG-T | 功能描述:电压模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| MAX1993EVKIT | 制造商:Maxim Integrated Products 功能描述:EVALUATION KIT FOR THE MAX1992 MAX1993 - Bulk |
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