参数资料
| 型号： | A8483EEK-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 6/10页 |
| 文件大小： | 0K |
| 描述： | IC REG BOOST ADJ 0.35A 5MLP |
| 标准包装： | 121 |
| 类型： | 升压（升压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 可调至 35V |
| 输入电压： | 2.5 V ~ 10 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 1.2MHz |
| 电流 - 输出： | 350mA |
| 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： | 5-WDFN 裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 5-MLP/TDFN（3x3） |
A8483
1.2 MHz Step-up Converter
for Display Bias Supply
Applications Information
Dimming Control
Display dimming can be achieved by controlling the output volt-
age, V OUT , using the FB pin. The circuitry behind the FB pin is
flexible, to accommodate a variety of schemes used for dimming:
? Adjust the duty cycle of the pulse train applied to the FB pin
through resistor R3, as shown in figure 11. Capacitor Cf is used
to generate the average voltage level. Variation of output volt-
age with PWM duty cycle is shown in figure 9.
? Apply a constant dc voltage to the FB pin through resistor R3,
as shown in figure 12. Variation of output voltage with dc volt-
age are shown in figure 10.
? Selection of the resistor connected between the FB pin and
Output voltage rise time at power-on can be extended by using a
soft start circuit, such as the one shown in figure 14 for an OLED
application, and in figure 16 for a WLED application. At power-
on, the device duty cycle begins initially at a high level, drawing
a large current from the input supply, VIN. The soft-start circuits
shown can reduce the level of current flow by controlling the FB
pin.
When a signal is applied to the EN pin, capacitor C3 discharges,
pulling the FB pin high, and reducing V OUT to a minimum. When
the EN signal is removed, C3 recharges and as it does, the voltage
drop across R3 reduces, allowing the device duty cycle to
GND, as shown in figure 12 for OLED applications, and in
figure 13 for WLED applications. The voltage drop across the
transistor should be negligible compared to the FB sense volt-
age.
V SUPPLY
C1
1 μF
5
VIN
L1
10 μH
A8483
1
SW
D1
V OUT
R1
560 k Ω
C2
1 μF
Soft Start
Li-ion
2.5 V to
EN
4
GND
2
FB
3
17
5.5 V
Enable
R3
160 k Ω
R2
47 k Ω
Cf
1 nF
15
13
Analog Voltage or
PWM 10 kHz
V C
Cf for PWM dimming only
11
9
Figure 11. OLED Bias Supply. Use for low-noise PWM dimming,
or with analog voltage through the FB pin.
7
L1
V OUT
5
5
VIN
10 μH
1
SW
D1
3
V SUPPLY
C1
1 μF
A8483
R1
560 k Ω
C2
10 μF
10 20 30 40 50 60 70 80 90
Duty Cycle (%)
Figure 9. PWM Dimming Control of Duty Cycle. Performance of 5 V input
circuit shown in figure 3.
Li-ion
2.5 V to
5.5 V
EN
4
Enable
GND
2
FB
3
R3
47 k Ω
V C
R2
47 k Ω
Cf
1 nF
Q1
20
18
16
14
Figure 12. OLED Dimming Control. Single-bit resolution using
external transistor.
V OUT
12
10
8
V SUPPLY
C1
5
VIN
L1
10 μH
A8483
1
SW
D1
6
4
2
0
Li-ion
2.5 V to
5.5 V
1 μF
EN
4
Enable
GND
2
FB
3
R2
80 Ω
R1
80 Ω
C2
0.22 μF
0.2
0.4
0.6
0.8
1
V C
V C (V)
Figure 10. DC Voltage Dimming Control of Duty Cycle. Performance of
circuit shown in figure 11.
Q1
Figure 13. WLED Dimming Control. Single-bit resolution using
external transistor.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
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