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| 型号： | MAX887HESA+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 10/12页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 0.6A 8SOIC |
| 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： | 1.25 V ~ 10 V |
| 输入电压： | 3.5 V ~ 11 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 300kHz |
| 电流 - 输出： | 600mA |
| 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 |
100% Duty Cycle, Low-Noise,
Step-Down, PWM DC-DC Converter
R1 = R2 ? OUT ? 1 ?
when to turn off this synchronous rectifier. A fourth
comparator (ILIM) is used at the P-channel MOSFET
switch for overcurrent detection. This protects the sys-
tem, external components, and internal MOSFETs
under overload conditions.
________________Design Information
Output Voltage Selection
To select an output voltage between 1.25V and 10.5V,
connect FB to a resistor voltage divider between the
output and GND (Figure 2). Select feedback resistor R2
in the 5k ? to 100k ? range, since FB input leakage is
±100nA max. R1 is then given by:
? V ?
? V FB ?
where V FB = 1.25V. A small ceramic capacitor (C1)
around 100pF to 470pF should be added in parallel
with R1 to compensate for stray capacitance at the FB
pin, and output capacitor equivalent series resistance
(ESR).
Inductor Selection
A 1.3A inductor with the value recommended in Table 1
is sufficient for most applications. However, the exact
inductor value is not critical, and values within 50% of
those in Table 1 are acceptable. For best efficiency, the
inductor’s DC resistance should be less than 0.25 ? .
The inductor saturation current rating must exceed the
ple and transient response. Lower oscillator frequen-
cies require a larger-value output capacitor. When Idle
Mode is used, verify capacitor selection with light loads
during PFM operation, since output ripple is higher
under these conditions.
Low-ESR capacitors are recommended. Capacitor ESR
is a major contributor to output ripple (usually more
than 60%). Ordinary aluminum-electrolytic capacitors
have high ESR and should be avoided. Low-ESR alu-
minum-electrolytic capacitors are acceptable and rel-
atively inexpensive. Low-ESR tantalum capacitors
are better and provide a compact solution for space-
constrained surface-mount designs. Do not exceed
the ripple current ratings of tantalum capacitors.
Ceramic capacitors have the lowest ESR overall, and
OS-CON capacitors have the lowest ESR of the high-
value electrolytic types. It is generally not necessary to
use ceramic and OS-CON capacitors for the MAX887;
they need only be considered in very compact, high-
reliability, or wide-temperature applications, where the
expense is justified. When using very-low-ESR capaci-
tors, such as ceramic or OS-CON, check for stability
while examining load-transient response, and increase
the compensation capacitor C1 if needed. Table 2 lists
suppliers for the various components used with the
MAX887.
Table 2. Component Suppliers
1A I LIM current limit. Table 2 lists component suppliers.
COMPANY
PHONE
FAX
Capacitor Selection
AVX
USA
(803) 946-0690
(803) 626-3123
Input and output filter capacitors should be chosen to
(800) 282-4975
service inductor currents with acceptable voltage rip-
ple. The input filter capacitor also reduces peak cur-
rents and noise at the voltage source. See Table 1 for
suggested values. The MAX887’s loop gain is relatively
low, to enable the use of small, low-valued output filter
capacitors. Higher values provide improved output rip-
Table 1. Inductor and Output Filter
vs. Sync Frequency
Coilcraft
Coiltronics
Dale
International
Rectifier
Motorola
Nichicon
Nihon
Sanyo
USA
USA
USA
USA
USA
USA
Japan
USA
Japan
USA
(847) 639-6400
(561) 241-7876
(605) 668-4131
(310) 322-3331
(602) 303-5454
(847) 843-7500
81-7-5231-8461
(805) 867-2555
81-3-3494-7411
(619) 661-6835
(847) 639-1469
(561) 241-9339
(605) 665-1627
(310) 322-3332
(602) 994-6430
(847) 843-2798
81-7-5256-4158
(805) 867-2698
81-3-3494-7414
(619) 661-1055
SYNC
L1
C OUT
Japan
81-7-2070-6306
81-7-2070-1174
RANGE (kHz)
(μH)
(μF)
Siliconix
USA
(408) 988-8000
(408) 970-3950
300–400
33
33
(800) 554-5565
200–300
150–200
100–150
47
68
100
47
68
100
Sprague
Sumida
United
USA
USA
Japan
USA
(603) 224-1961
(847) 956-0666
81-3-3607-5111
(714) 255-9500
(603) 224-1430
(847) 956-0702
81-3-3607-5144
(714) 255-9400
75–100
150
150
Chemi-Con
10
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