参数资料
型号: MAX8874SEUK+T
厂商: Maxim Integrated
文件页数: 7/10页
文件大小: 0K
描述: IC REG LDO 2.84V/ADJ SOT23-5
产品培训模块: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
标准包装: 2,500
稳压器拓扑结构: 正,固定式或可调式
输出电压: 2.84V,1.25 V ~ 6.5 V
输入电压: 2.5 V ~ 6.5 V
电压 - 压降(标准): 0.055V @ 50mA
稳压器数量: 1
电流 - 输出: 120mA(最小)
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: SC-74A,SOT-753
供应商设备封装: SOT-23-5
包装: 带卷 (TR)
MAX8873T/S/R, MAX8874T/S/R
Low-Dropout, 120mA Linear Regulators
Choose R2 = 100k Ω to optimize power consumption,
accuracy, and high-frequency power-supply rejection.
OUTPUT
The total current through the external resistive feedback
1
IN
OUT
5
VOLTAGE
and load resistors should not be less than 10μA. Since
the V SET tolerance is typically less than ±25mV, the out-
C IN
BATTERY 1 μ F
3
MAX8873
MAX8874
SHDN
GND
2
SET
4
R1 20pF
R2
C OUT
1 μ F
R L
put can be set using fixed resistors instead of trim pots.
Connect a 10pF to 25pF capacitor across R1 to com-
pensate for layout-induced parasitic capacitances.
In preset voltage mode, impedances between SET and
ground should be less than 100k Ω . Otherwise, spurious
conditions could cause the voltage at SET to exceed
the 60mV dual-mode threshold.
Shutdown
A low input on the SHDN pin shuts down the
Figure 2. Adjustable Output Using External Feedback
Resistors
Internal P-Channel Pass Transistor
The MAX8873/MAX8874 feature a 1.1 Ω typical P-chan-
nel MOSFET pass transistor. This provides several
advantages over similar designs using PNP pass tran-
sistors, including longer battery life.
The P-channel MOSFET requires no base drive current,
which reduces quiescent current considerably. PNP-
based regulators waste considerable amounts of cur-
rent in dropout when the pass transistor saturates. They
also use high base-drive currents under large loads.
The MAX8873/MAX8874 do not suffer from these prob-
lems, and consume only 82μA of quiescent current,
whether in dropout, light load, or heavy load applica-
tions (see Typical Operating Characteristics).
Output Voltage Selection
The MAX8873/MAX8874 feature Dual Mode operation:
they operate in either a preset voltage mode or an
adjustable mode.
In preset voltage mode, internal, trimmed feedback
resistors set the MAX887_R output to 2.80V, the
MAX887_S output to 2.84V, and the MAX887_T output to
3.15V. Select this mode by connecting SET to ground.
In adjustable mode, select an output between 1.25V
and 6.5V using two external resistors connected as a
voltage divider to SET (Figure 2). The output voltage is
set by the following equation:
V OUT = V SET (1 + R1 / R2)
where V SET = 1.25V. To simplify resistor selection:
MAX8873/MAX8874. In shutdown mode, the pass tran-
sistor, control circuit, reference, and all biases are
turned off, reducing the supply current to typically
0.1nA. Connect SHDN to IN for normal operation. The
MAX8874 output voltage is actively discharged to
ground when the part is placed in shutdown (see
Typical Operating Characteristics).
Current Limit
The MAX8873/MAX8874 include a current limiter that
monitors and controls the pass transistor’s gate volt-
age, estimating the output current and limiting it to
about 280mA. For design purposes, the current limit
should be considered 120mA to 420mA. The output
can be shorted to ground for an indefinite time period
without damaging the part.
Thermal Overload Protection
Thermal overload protection limits total power dissipa-
tion in the MAX8873/MAX8874. When the junction tem-
perature exceeds T J = +170°C, the thermal sensor
sends a signal to the shutdown logic, turning off the
pass transistor and allowing the IC to cool. The thermal
sensor turns the pass transistor on again after the IC’s
junction temperature typically cools by 20°C, resulting
in a pulsed output during continuous thermal overload
conditions.
Thermal overload protection is designed to protect the
MAX8873/MAX8874 in the event of fault conditions.
Stressing the device with high load currents and high
input-output differential voltages (which result in die tem-
peratures above +125°C) may cause a momentary over-
shoot (2% to 8% for 200ms) when the load is completely
removed. This can be remedied by raising the minimum
load current from 0μA (+125°C) to 100μA (+150°C). For
? V
? V SET
? 1 ?
?
Maxim Integrated
R1 = R2 ? OUT
?
?
?
continuous operation, do not exceed the absolute maxi-
mum junction temperature rating of T J = +150°C.
7
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