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| 型号： | A4490EES-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 10/17页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 1.5A TRPL 20QFN |
| 标准包装： | 92 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 3 |
| 输出电压： | 可调 |
| 输入电压： | 4.5 V ~ 34 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 550kHz |
| 电流 - 输出： | 1.5A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-WFQFN 裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 20-QFN 裸露焊盘（4x4） |
| 配用： | 620-1388-ND - BOARD EVAL FOR A4490 |
| 其它名称： | A4490SES-T A4490SES-T-ND |
A4490
Triple Output Step-Down Switching Regulator
The bias current, I BIAS , flowing out of the FB1 node into R2, will
introduce a small voltage offset to the output.
Enable Each regulator channel can be individually enabled via
the corresponding ENBx pin. If any channel is required to start-
up automatically after the VBB voltage is applied, that particu-
lar channel should have the ENB pin tied to the VBB rail via a
pullup resistor.
This resistor should be selected to limit the current to less than
the maximum specified value, 1 mA. This prevents the internal
protection clamps from turning on. It is recommended that a
100 k Ω pull-up resistor be used. This would ensure the current
remains below the maximum value when V BB = 36 V.
Soft Start Each regulator channel contains a soft start circuit. A
soft start cycle is initiated when the appropriate regulator enable
input is set to high; the V BB , charge pump, and bias supply volt-
ages are above the minimum values; and no thermal shutdown
condition exists. Note that an overload or short circuit will not
cause a soft start cycle, unless a thermal shutdown event occurs.
During a soft start cycle, the reference voltage is ramped from
0 to 0.8 V typical, which in turn forces the current demand signal
to increase in a linear fashion.
Shutdown All converter channels are disabled in the event of
either a thermal shutdown event or an undervoltage on VBB
(V BBUV(sd) or V BBCPUV(sd) ).
As soon as the above fault conditions have been removed, and
assuming the ENB inputs are enabled, the appropriate channels
will auto-restart under control of the soft start.
Current Limit The typical peak current limit for each channel is
specified as 2.5 A minimum, with a duty cycle of 0.9. The mini-
mum current limit occurs at maximum duty cycle (0.9), because
the slope compensation has a maximum effect under this condi-
tion. As the duty cycle reduces, the current limit increases. This
means for applications that operate with a narrow duty cycle, it is
possible to operate with a load current greater than 2.0 A.
Figure 3 illustrates the typical peak current limit versus duty
to check the implications on the thermal performance. See the
Thermal Considerations section.
Component Selection
Inductor The inductance value, L, determines the ripple current.
It is important to ensure that the minimum current limit is not
exceeded under worst-case conditions: V BB (min), I LOAD (max),
f SW (min), and L(min).
It is recommended that gapped ferrite solutions be used as
opposed to powdered iron solutions, the latter of which exhibit
relatively high core losses that can have a large impact on long
term reliability.
Inductors are typically specified at two current levels, rms cur-
rent and saturation current. With regard to the rms current, it is
important to understand how the rms current level is specified,
in terms of ambient temperature. Some manufacturers quote an
ambient only, whilst others quote a temperature that includes a
self-induced temperature rise. For example, if an inductor is rated
for 85°C and includes a self-induced temperature rise of 25°C
at maximum load, then the inductor cannot be safely operated
beyond an ambient temperature of 60°C at full load. The rms cur-
rent can be assumed to be simply the maximum load current, with
perhaps some margin to allow for overloads, and so forth.
The first stage of determining the inductor value is to specify a
peak-to-peak ripple current of typically about 20% to 25% of the
maximum load.
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
0.5
1.0
0.5
0
cycle. For example, it is possible to operate with a peak current
0
20
40
60
80
100
limit of 3.75 A with a duty cycle of 0.3.
As well as ensuring the peak current limit is not exceeded, under
worst case load and input voltage conditions, it is also important
Duty Cycle (%)
Figure 3. Current limit versus duty cycle
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
10
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相关代理商/技术参数 |
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| A4490EESTRT | 制造商:ALLEGRO 功能描述:Pb Free |
| A4490EESTR-T | 功能描述:IC REG BUCK ADJ 1.5A TRPL 20QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 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:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| A4491 | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:Designed to provide the power supply requirements of printers, office automation, industrial, and portable equipment, the A4491 provides three high current, |
| A4491EESTR-T | 功能描述:IC REG BUCK ADJ 2.2A TRPL 20QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:50 系列:- 类型:升压（升压） 输出类型:可调式 输出数:1 输出电压:5 V ~ 25 V 输入电压:2.3 V ~ 5.5 V PWM 型:电流模式 频率 - 开关:600kHz，1.2MHz 电流 - 输出:1A 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-TSSOP，8-MSOP（0.118"，3.00mm 宽） 包装:管件 供应商设备封装:8-MSOP |
| A4492 | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:Designed to provide the power supply requirements for automotive applications, the A4492 provides three high current, high performance, switching regulator outputs with independent soft start. |
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