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| 型号： | MAX1688ESA+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 9/12页 |
| 文件大小： | 0K |
| 描述： | IC REG BOOST SYNC ADJ 2.5A 8SOIC |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 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： | 1.25 V ~ 6 V |
| 输入电压： | 2.7 V ~ 6 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 1MHz |
| 电流 - 输出： | 2.5A |
| 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： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-SOIC |
Step-Up DC-DC Converters with
Precise, Adaptive Current Limit for GSM
between CHG and GND controls the output recharge
a)
MAX1687
b)
MAX1687
time. A large resistor increases peak inductor current
which speeds up recovery time. Calculate the resistor
as follows:
( ) ? + 0.1 ? ?
? V
? D
? ?
R CHG = ? ?
( )
??
?? V
? 1-D
? ?
?
?
?
V IN(MIN)
?
?
?
?
(
)
?
REF
LIM
c)
R3
R4
REF
LIM
DAC
MAX1687
LIM
V LIM(CHG) = V REF
R3 + R4 > 125k ?
R4
R4 + R3
? I BURST OUT GSM
?
?
?
?
? V DROOP gm CHG V REF gm FB
?
IN(MIN) GSM ?
?
?
?
1 - tol ?
where:
Figure 5. Current-Limit Adjust
To set the current limit, apply a voltage of 0 to 1V at
LIM. The current limit is 200mA when V LIM = 0 to
0.25V. Use the following equation to calculate I LIM :
I LIM = V LIM (0.86A/V) – 0.06A
where V LIM = 0.25V to 1V.
V LIM is internally clamped to 1.25V when the voltage
applied at V LIM is above 1.25V. Generate V LIM by one
of three methods: an externally applied voltage, the
output of a DAC, or a resistor-divider using V REF as the
supply voltage (TSSOP packages) (Figure 5). Note that
REF can supply up to 10μA.
Determine V LIM as follows:
V LIM = (I LX(PEAK) + 0.06A) / 0.86
where I LX(PEAK) = [(I LOAD · V OUT ) / V IN ] + 0.1A (see
the Inductor Current parameter in the Typical Operating
Characteristics).
Setting Recharge Time (MAX1688)
The MAX1688 has a recharging feature employing a
sample-and-hold, which sets the maximum time to
recharge the reservoir capacitor. Synchronize the ON
pin to place the converter in standby during each load
current burst. At the end of each load current burst, the
output voltage is sampled by the MAX1688. This volt-
age controls the peak inductor current. The greater the
difference between the regulated output voltage and
the valley of the sag voltage, the higher the peak cur-
rent. This results in a constant recharge time that com-
pensates for varying output filter capacitor character-
istics as well as a varying input voltage. Therefore, the
circuit demands only as much peak current from the
battery as output conditions require, minimizing the
peak current from the battery. An external resistor
R CHG is the external resistor
I BURST is the peak burst current expected
D GSM is the duty cycle of GSM
V IN is the input voltage
V OUT is the output voltage
V REF = 1.25V
V DROOP is the drop in output voltage during the cur-
rent burst
g mCHG is the internal transconductance = 0.8A/V
g mFB is the feedback transconductance = 200μA/V
tol is the tolerance of the R CHG resistor
For example, for I BURST = 2.66A, V DROOP = 0.36V, V IN
= +2.7V, and V OUT = 3.6V, then R CHG = 31.5k ? , using
a 5% tolerance resistor.
The recovery time for a 40.2k ? R CHG is shorter than
that with an 18k ? R CHG , but the peak battery current is
higher. See Switching Waveforms (GSM Pulsed Load
1A, R CHG = 40.2k ? ) and Switching Waveforms (GSM
Pulsed Load 1A, R CH = 18k ? ) in Typical Operating
Characteristics.
Inductor Selection
The value of the inductor determines the switching fre-
quency. Calculate the switching frequency as:
f = V IN [1 - (V IN / V OUT )] / (L · I RIPPLE )
where f is the switching frequency, V IN is the input volt-
age, V OUT is the output voltage, L is the inductor value,
and I RIPPLE is the ripple current expected, typically
0.2A. Using a lower value inductor increases the fre-
quency and reduces the physical size of the inductor.
A typical frequency is from 150kHz to 1MHz (see
Switching Frequency vs. Inductance in the Typical
Operating Characteristics).
_______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1688EUE | 功能描述:直流/直流开关转换器 StepUp w/Prec Adapt Crnt Limit for GSM 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 |
| MAX1688EUE+ | 功能描述:直流/直流开关转换器 StepUp w/Prec Adapt Crnt Limit for GSM 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 |
| MAX1688EUE+T | 功能描述:直流/直流开关转换器 StepUp w/Prec Adapt Crnt Limit for GSM 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 |
| MAX1688EUE-T | 功能描述:直流/直流开关转换器 StepUp w/Prec Adapt Crnt Limit for GSM 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 |
| MAX1688EUE-T | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
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