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参数资料
| 型号： | MAX1857EUA47 |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | 基准电压源/电流源 |
| 英文描述： | 500mA, Low-Dropout, Ripple-Rejecting LDO in MAX |
| 中文描述： | FIXED/ADJUSTABLE POSITIVE LDO REGULATOR, 0.175 V DROPOUT, PDSO8 |
| 封装： | MICRO MAX PACKAGE-8 |
| 文件页数： | 8/10页 |
| 文件大小： | 245K |
| 代理商： | MAX1857EUA47 |
M
shut down,
RST
is held low independent of the output
voltage. If unused, leave
RST
grounded or unconnected.
Current Limit
The MAX1857 monitors and controls the pass transis-
tor
’
s gate voltage, limiting the output current to 1.2A.
This current limit doubles when the output voltage is
within 4% of the nominal value to improve performance
with large load transients. The output can be shorted to
ground for an indefinite period of time without damag-
ing the part.
Thermal Overload Protection
Thermal overload protection limits total power dissipa-
tion in the MAX1857. When the junction temperature
exceeds T
J
= +170
°
C, a thermal sensor turns off the
pass transistor, allowing the device to cool. The thermal
sensor turns the pass transistor on again after the junc-
tion temperature cools by 20
°
C, resulting in a pulsed
output during continuous thermal overload conditions.
Thermal overload protection protects the MAX1857 in
the event of fault conditions. For continuous operation,
do not exceed the absolute maximum junction-temper-
ature rating of T
J
= +150
°
C.
Operating Region and
Power Dissipation
The MAX1857
’
s maximum power dissipation depends on
the thermal resistance of the IC package and circuit
board, the temperature difference between the die junc-
tion and ambient air, and the rate of air flow. The power
dissipated in the device is P = I
OUT
x (V
IN
- V
OUT
). The
maximum allowed power dissipation is 330mW or:
P
MAX
= (T
J(MAX)
- T
A
) / (
θ
JC
+
θ
CA
)
where T
J
- T
A
is the temperature difference between
the MAX1857 die junction and the surrounding air;
θ
JC
is the thermal resistance from the junction to the case;
and
θ
CA
is the thermal resistance from the case
through the PC board, copper traces, and other materi-
als to the surrounding air.
The MAX1857 delivers up to 0.5A
RMS
and operates with
input voltages up to 5.5V, but not simultaneously. High
output currents can only be sustained when input-output
differential voltages are low, as shown in Figure 3.
Applications Information
Capacitor Selection
and Regulator Stability
Capacitors are required at the MAX1857
’
s input and
output for stable operation over the full temperature
range and with load currents up to 500mA. Connect a
1μF capacitor between IN and ground and a 3.3μF low
equivalent series resistance (ESR) capacitor between
OUT and ground. For output voltages less than 2V, use
a 4.7μF low-ESR output capacitor. The input capacitor
(C
IN
) lowers the source impedance of the input supply.
Reduce noise and improve load-transient response,
stability, and power-supply rejection by using larger
output capacitors such as 10μF.
The output capacitor
’
s (C
OUT
) ESR affects stability and
output noise. Use output capacitors with an ESR of
0.1
or less to ensure stability and optimum transient
response. Surface-mount ceramic capacitors have very
low ESR and are commonly available in values up to
10μF. Connect C
IN
and C
OUT
as close to the MAX1857
as possible to minimize the impact of PC board trace
inductance.
Noise, PSRR, and Transient Response
The MAX1857 is designed to operate with low dropout
voltages and low quiescent currents in battery-powered
systems while still maintaining good noise, transient
response, and AC rejection. See the
Typical Operating
Characteristics
for a plot of power-supply rejection ratio
(PSRR) vs. frequency. When operating from noisy
sources, improved supply-noise rejection and transient
response can be achieved by increasing the values of
the input and output bypass capacitors and through
passive filtering techniques.
The MAX1857 load-transient response graphs (see
Typical Operating Characteristics
) show two compo-
500mA, Low-Dropout,
Ripple-Rejecting LDO in μMAX
8
_______________________________________________________________________________________
Figure 3. Power Operating Regions: Maximum Output Current
vs. Supply Voltage
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
M
4.0
4.5
0
0.5
3.5
3.0
2.5
2.0
1.5
1.0
INPUT-OUTPUT VOLTAGE DIFFERENTIAL (V)
MAXIMUM SUPPLY
VOLTAGE LIMIT
(V
OUT
= 1.25V)
μ
MAX PACKAGE OPERATING
REGION AT T
J(MAX)
= +150
°
C
T
A
= +50
°
C
T
A
= +70
°
C
T
A
= +85
°
C
CONTINUOUS CURRENT LIMIT
T
D
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相关代理商/技术参数 |
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|---|---|
| MAX1857EUA47+ | 功能描述:低压差稳压器 - LDO 500mA Ripple-Rejecting RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| MAX1857EUA47+T | 功能描述:低压差稳压器 - LDO 500mA Ripple-Rejecting RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| MAX1857EUA47-T | 功能描述:低压差稳压器 - LDO 500mA Ripple-Rejecting RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| MAX1858AEEG | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1858AEEG+ | 功能描述:电压模式 PWM 控制器 Dual 180 Out Buck Controllers RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
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