- 您现在的位置：买卖IC网 > PDF目录1838 > MAX1644EAE-T (Maxim Integrated Products)IC REG BUCK SYNC ADJ 2A 16SSOP PDF资料下载
参数资料
| 型号： | MAX1644EAE-T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 6/11页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 2A 16SSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,000 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.1 V ~ 5.5 V |
| 输入电压： | 3 V ~ 5.5 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 最高 350kHz |
| 电流 - 输出： | 2A |
| 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： | 16-SSOP（0.209"，5.30mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 16-SSOP |
2A, Low-Voltage, Step-Down Regulator with
Synchronous Rectification and Internal Switches
_______________Detailed Description
The MAX1644 synchronous, current-mode, constant-off-
time, PWM DC-DC converter steps down input voltages
of +3V to +5.5V to a preset output voltage of either +3.3V
or +2.5V, or to an adjustable output voltage from +1.1V
to V IN . The device delivers up to 2A of continuous load
current. Internal switches composed of a 0.1 Ω PMOS
power switch and a 0.1 Ω NMOS synchronous-rectifier
switch improve efficiency, reduce component count, and
eliminate the need for an external Schottky diode.
The MAX1644 optimizes performance by operating in
constant-off-time mode under heavy loads and in
Maxim’s proprietary Idle Mode under light loads. A sin-
gle resistor-programmable constant-off-time control
sets switching frequencies up to 350kHz, allowing the
user to optimize performance trade-offs in efficiency,
switching noise, component size, and cost. Under low-
dropout conditions, the device operates in a 100%
duty-cycle mode, where the PMOS switch remains per-
manently on. Idle Mode enhances light-load efficiency
by skipping cycles, thus reducing transition and gate-
charge losses.
When power is drawn from a regulated supply, constant-
off-time PWM architecture essentially provides constant-
frequency operation. This architecture has the inherent
advantage of quick response to line and load transients.
The MAX1644’s current-mode, constant-off-time PWM
architecture regulates the output voltage by changing
the PMOS switch on-time relative to the constant off-
time. Increasing the on-time increases the peak induc-
tor current and the amount of energy transferred to the
load per pulse.
Modes of Operation
The current through the PMOS switch determines the
mode of operation: constant-off-time mode (for load
currents greater than 0.2A) or Idle Mode (for load cur-
rents less than 0.2A). Current sense is achieved
through a proprietary architecture that eliminates cur-
rent-sensing I 2 R losses.
Constant-Off-Time Mode
Constant-off-time operation occurs when the current
through the PMOS switch is greater than the Idle Mode
threshold current (0.4A, which corresponds to a load
current of 0.2A). In this mode, the regulation compara-
tor turns the PMOS switch on at the end of each off-
time, keeping the device in continuous-conduction
mode. The PMOS switch remains on until the output is
in regulation or the current limit is reached. When the
PMOS switch turns off, it remains off for the pro-
grammed off-time (t OFF ). If the output falls dramatically
out of regulation—approximately V FB / 4—the PMOS
switch remains off for approximately four times t OFF .
The NMOS synchronous rectifier turns on shortly after
the PMOS switch turns off, and it remains on until short-
ly before the PMOS switch turns back on.
Idle Mode
Under light loads, the device improves efficiency by
switching to a pulse-skipping Idle Mode. Idle Mode
operation occurs when the current through the PMOS
switch is less than the Idle Mode threshold current. Idle
Mode forces the PMOS to remain on until the current
through the switch reaches 0.4A, thus minimizing the
unnecessary switching that degrades efficiency under
light loads. In Idle Mode, the device operates in discon-
tinuous conduction. Current-sense circuitry monitors the
current through the NMOS synchronous switch, turning it
off before the current reverses. This prevents current
from being pulled from the output filter through the
inductor and NMOS switch to ground. As the device
switches between operating modes, no major shift in cir-
cuit behavior occurs.
100% Duty-Cycle Operation
When the input voltage drops near the output voltage,
the duty cycle increases until the PMOS MOSFET is on
continuously. The dropout voltage in 100% duty cycle
is the output current multiplied by the on-resistance of
the internal PMOS switch and parasitic resistance in the
inductor. The PMOS switch remains on continuously as
long as the current limit is not reached.
Shutdown
Drive SHDN to a logic-level low to place the MAX1644
in low-power shutdown mode and reduce supply cur-
rent to less than 1μA. In shutdown, all circuitry and
internal MOSFETs turn off, and the LX node becomes
high impedance. Drive SHDN to a logic-level high or
connect to V CC for normal operation.
Summing Comparator
Three signals are added together at the input of the
summing comparator (Figure 1): an output voltage error
signal relative to the reference voltage, an integrated
output voltage error correction signal, and the sensed
PMOS switch current. The integrated error signal is pro-
vided by a transconductance amplifier with an external
capacitor at COMP. This integrator provides high DC
accuracy without the need for a high-gain amplifier.
Connecting a capacitor at COMP modifies the overall
loop response (see the Integrator Amplifier section).
6
_______________________________________________________________________________________
相关PDF资料 |
PDF描述 |
|---|---|
| MAX1651CSA | IC REG CTRLR BUCK PWM 8-SOIC |
| MAX1653EEE-T | IC REG CTRLR BUCK PWM CM 16-QSOP |
| MAX1659ESA+ | IC REG LDO 5V/ADJ .35A 8-SOIC |
| MAX1667EAP+T | IC SMART BATT CHGR LEVEL2 20SSOP |
| MAX1672EEE-T | IC REG BUCK BOOST FIX/ADJ 16QSOP |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1644EVKIT | 功能描述:电源管理IC开发工具 Evaluation Kit for the MAX1644 RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| MAX1645AEEI | 功能描述:电池管理 RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| MAX1645AEEI+T | 功能描述:电池管理 RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| MAX1645AEEI-T | 功能描述:电池管理 RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| MAX1645AEVSYS | 制造商:Maxim Integrated Products 功能描述:KIT PKG - Bulk |
发布紧急采购，3分钟左右您将得到回复。