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| 型号： | MAX8805YEWEBE+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 14/24页 |
| 文件大小： | 0K |
| 描述： | IC CONV STP-DN PWM 600MA 16WLP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 应用： | 转换器，WCDMA PA 电源 |
| 输入电压： | 2.7 V ~ 5.5 V |
| 输出数： | 1 |
| 输出电压： | 0.4 V ~ 5.5 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-UFBGA，WLCSP |
| 供应商设备封装： | 16-WLP（2x2） |
| 包装： | 带卷 (TR) |
600mA/650mA PWM Step-Down Converters in
2mm x 2mm WLP for WCDMA PA Power
Detailed Description
The MAX8805W/MAX8805X/MAX8805Y/MAX8805Z are
designed to dynamically power the PA in WCDMA and
NCDMA handsets. The devices contain a high-frequency,
high-efficiency step-down converter, and two LDOs.
The MAX8805Y/MAX8805Z step-down converters deliver
over 600mA, while the MAX8805W/MAX8805X deliver
over 650mA. The hysteretic PWM control scheme pro-
vides extremely fast transient response, while 2MHz and
4MHz switching-frequency options allow the trade-off
between efficiency and the smallest external compo-
nents. A 60m ? bypass FET connects the PA directly to
the battery during high-power transmission.
Step-Down Converter Control Scheme
A hysteretic PWM control scheme ensures high effi-
ciency, fast switching, fast transient response, low-out-
put ripple, and physically tiny external components.
The control scheme is simple: when the output voltage
is below the regulation threshold, the error comparator
begins a switching cycle by turning on the high-side
switch. This high-side switch remains on until the mini-
mum on-time expires and the output voltage is within
Step-Down Converter Bypass Mode
During high-power transmission, the bypass mode con-
nects IN1A and IN1B directly to PAA and PAB with the
internal 60m ? (typ) bypass FET, while the step-down
converter is forced into 100% duty-cycle operation. The
low on-resistance in this mode provides low dropout,
long battery life, and high output current capability.
Forced and Automatic Bypass Mode
Invoke forced bypass mode by driving HP high or
invoke automatic bypass mode by applying a high volt-
age to REFIN. To prevent excessive output ripple as
the step-down converter approaches dropout, the
MAX8805Y/MAX8805Z enter bypass mode automatical-
ly when V REFIN > 0.465 x V IN2 (see Figure 2) and
MAX8805W/MAX8805X enter bypass mode automati-
cally when V REFIN > 0.372 x V IN2 . Note that IN2 is used
instead of IN1 to prevent switching noise from causing
false enagement of automatic bypass mode. For this
reason, IN2 must be connected to the same source
as IN1.
regulation, or the inductor current is above the current-
limit threshold. Once off, the high-side switch remains
off until the minimum off-time expires and the output
voltage falls again below the regulation threshold.
During the off period, the low-side synchronous rectifier
turns on and remains on until the high-side switch turns
on again. The internal synchronous rectifier eliminates
the need for an external Schottky diode.
Voltage-Positioning Load Regulation
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
2.5
2.0
1.5
1.0
The MAX8805W/MAX8805X/MAX8805Y/MAX8805Z step-
1.0
IN2
0.5
down converters utilize a unique feedback network. By
taking DC feedback from the LX node through R1 in
Figure 1, the usual phase lag due to the output capacitor
0.5
0
0
5
PA_
REFIN
10 15 20 25 30 35 40 45 50
0
is removed, making the loop exceedingly stable and
allowing the use of very small ceramic output capacitors.
To improve the load regulation, resistor R3 is included in
the feedback. This configuration yields load regulation
equal to half of the inductor’s series resistance multiplied
by the load current. This voltage-positioning load regula-
tion greatly reduces overshoot during load transients or
when changing the output voltage from one level to anoth-
er. However, when calculating the required REFIN volt-
age, the load regulation should be considered. Because
inductor resistance is typically well specified and the
typical PA is a resistive load, the MAX8805Y/MAX8805Z
V REFIN to V OUT gain is slightly less than 2V/V, and the
MAX8805W/MAX8805X V REFIN to V OUT gain is slightly
less than 2.5V/V. The output voltage is aproximately:
V OUT = (REFIN to PA_Gain) x V REFIN - 1/2 x L ESR x I LOAD
TIME (ms)
Figure 2. V IN2 and V PA_ with Automatic Entry/Exit into Bypass
Mode (MAX8805Y/MAX8805Z)
Shutdown Mode
Connect PA_EN to GND or logic-low to place the
MAX8805W/MAX8805X/MAX8805Y/MAX8805Z PA
step-down converter in shutdown mode. In shutdown,
the control circuitry, internal switching MOSFET, and
synchronous rectifier turn off and LX becomes high
impedance. Connect PA_EN to IN1_ or logic-high for
normal operation.
Connect EN1 or EN2 to GND or logic-low to place
LDO1 or LDO2, respectively, in shutdown mode. In
14
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8805YEWEBG+T | 功能描述:直流/直流开关转换器 600mA/650mA PWM Step-Down Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX8805YEWECC+T | 功能描述:直流/直流开关转换器 600mA/650mA PWM Step-Down Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX8805YEWECD+T | 功能描述:直流/直流开关转换器 600mA/650mA PWM Step-Down Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX8805YEWECE+T | 功能描述:直流/直流开关转换器 600mA/650mA PWM Step-Down Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX8805YEWEDD+T | 功能描述:直流/直流开关转换器 600mA/650mA PWM Step-Down Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
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