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| 型号： | MAX8646ETG+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 10/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 6A 24TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.6 V ~ 3.2 V |
| 输入电压： | 2.35 V ~ 3.6 V |
| PWM 型： | 电压模式 |
| 频率 - 开关： | 500kHz ~ 2MHz |
| 电流 - 输出： | 6A |
| 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： | 24-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 24-TQFN-EP（4x4） |
6A, 2MHz Step-Down Regulator
with Integrated Switches
voltage exceeds the V COMP signal or the current-limit
threshold is exceeded. The low-side switch is then
turned on for the remainder of the oscillator cycle.
Current Limit
The internal, high-side MOSFET has a typical 11A peak
current-limit threshold. When current flowing out of LX
exceeds this limit, the high-side MOSFET turns off and
the synchronous rectifier turns on. The synchronous
rectifier remains on until the inductor current falls below
the low-side current limit. This lowers the duty cycle
and causes the output voltage to droop until the current
limit is no longer exceeded. The MAX8646 uses a hic-
cup mode to prevent overheating during short-circuit
BST
The gate-drive voltage for the high-side, n-channel
switch is generated by a flying-capacitor boost circuit.
The capacitor between BST and LX is charged from the
V IN supply while the low-side MOSFET is on. When the
low-side MOSFET is switched off, the voltage of the
capacitor is stacked above LX to provide the necessary
turn-on voltage for the high-side internal MOSFET.
Frequency Select (FREQ)
The switching frequency is resistor programmable from
500kHz to 2MHz. Set the switching frequency of the IC
with a resistor (R FREQ ) connected from FREQ to GND.
R FREQ is calculated as:
× (
output conditions.
During current limit if V FB drops below 420mV and
stays below this level for 12μs or more, the part enters
R FREQ =
49 . 9 k ? 1
0 . 95 μs f S
? 0 . 05 μs )
hiccup mode. The high-side MOSFET and the synchro-
nous rectifier are turned off and both COMP and REFIN
are internally pulled low. If REFIN and SS are connect-
ed together, then both are pulled low. The part remains
in this state for 1024 clock cycles and then attempts to
restart for 128 clock cycles. If the fault causing current
limit has cleared, the part resumes normal operation.
Otherwise, the part reenters hiccup mode again.
Soft-Start and REFIN
The MAX8646 utilizes an adjustable soft-start function
to limit inrush current during startup. An 8μA (typ) cur-
rent source charges an external capacitor connected to
SS. The soft-start time is adjusted by the value of the
external capacitor from SS to GND. The required
capacitance value is determined as:
where f S is the desired switching frequency in Hz.
Power-Good Output (PWRGD)
PWRGD is an open-drain output that goes high imped-
ance when V FB is above 0.9 x V REFIN . PWRGD pulls
low when V FB is below 90% of its regulation for at least
48 clock cycles. PWRGD is low during shutdown.
Programming the Output Voltage
(CTL1, CTL2)
As shown in Table 1, the output voltage is pin program-
mable by the logic states of CTL1 and CTL2. CTL1 and
CTL2 are tri-level inputs: V DD , unconnected, and GND.
The logic states of CTL1 and CTL2 should be pro-
grammed only before power-up. Once the part is
enabled, CTL1 and CTL2 should not be changed. If the
C =
8 μ A × t SS
0 . 6 V
output voltage needs to be reprogrammed, cycle
power or EN and reprogram before enabling.
where t SS is the required soft-start time in seconds. The
MAX8646 also features an external reference input
(REFIN). The IC regulates FB to the voltage applied to
REFIN. The internal soft-start is not available when
using an external reference. A method of soft-start
when using an external reference is shown in Figure 2.
Connect REFIN to SS to use the internal 0.6V reference.
R1
REFIN
Undervoltage Lockout (UVLO)
R2
C
MAX8646
The UVLO circuitry inhibits switching when V DD is below
2V (typ). Once V DD rises above 2V (typ), UVLO clears
and the soft-start function activates. A 100mV hysteresis
is built in for glitch immunity. Figure 3 is the type III com-
pensation network.
Figure 2. Typical Soft-Start Implementation with External
Reference
10
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相关代理商/技术参数 |
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| MAX8646EVKIT+ | 功能描述:直流/直流开关调节器 Evaluation Kit for the MAX8646 RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MAX8647ETE+ | 功能描述:LED照明驱动器 Charge Pump for 6 White/RGB LEDs RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| MAX8647ETE+T | 功能描述:LED照明驱动器 Charge Pump for 6 White/RGB LEDs RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| MAX8648ETE | 制造商:MAXIM 功能描述:Pb Free |
| MAX8648ETE+ | 功能描述:LED照明驱动器 Charge Pump for 6 White/RGB LEDs RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
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