参数资料
| 型号： | SC4524DSETRT |
| 厂商： | Semtech |
| 文件页数： | 12/22页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 2A 8SOIC |
| 标准包装： | 1 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1 V ~ 17.28 V |
| 输入电压： | 3 V ~ 18 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 300kHz ~ 1.3MHz |
| 电流 - 输出： | 2A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 105°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm Width）裸露焊盘 |
| 包装： | 标准包装 |
| 供应商设备封装： | 8-SOIC-EP |
| 其它名称： | SC4524DSEDKR |
SC4524D
Applications Information (Cont.)
Freewheeling Diode
Use of Schottky barrier diodes as freewheeling rectifiers
reduces diode reverse recovery input current spikes,
A small ceramic capacitor (0.33uF - 0.47uF) is adequate for
bootstrapping.
easing high-side current sensing in the SC4524D. These
diodes should have an average forward current rating
at least 2A and a reverse blocking voltage of at least a
few volts higher than the input voltage. For switching
regulators operating at low duty cycles (i.e. low output
voltage to input voltage conversion ratios), it is beneficial
to use freewheeling diodes with somewhat higher
average current ratings (thus lower forward voltages). This
is because the diode conduction interval is much longer
than that of the transistor. Converter efficiency will be
2.2
2.1
2.0
1.9
1.8
1.7
Minimum Bootstrap Voltage
vs Temperature
I S W = -2 .6 A
improved if the voltage drop across the diode is lower.
1.6
-50
-25
0
25
50
75
100
125
The freewheeling diode should be placed close to the
SW pin of the SC4524D to minimize ringing due to trace
inductance. 20BQ030 (International Rectifier), B230A
(Diodes Inc.), SS13, SS23 (Vishay), CMSH1-40M, CMSH1-
40ML and CMSH2-40M (Central-Semi.) are all suitable.
Temperature ( o C)
Figure 5 — Typical Minimum Bootstrap Voltage
required to Saturate Transistor (I SW = -2.6A).
D1
The freewheeling diode should be placed close to the SW
pin of the SC4524D on the PCB to minimize ringing due to
trace inductance.
Bootstrapping the Power Transistor
V IN
BST
IN SW
SC4524D
GND
D2
C1
3V < V O < 8V
The typical minimum BST-SW voltage required to fully
saturate the power transistor is shown in Figure 5, which
is about 1.96V at room temperature.
D1
(a)
The BST-SW voltage is supplied by a bootstrap circuit
powered from either the input or the output of the
V IN
IN
BST
SW
C1
V O < 2 .5 V
converter (Figure 6(a), 6(b) and 6(c)). To maximize
efficiency, tie the bootstrap diode to the converter output
if V O > 2.5V as shown in Figure 6(a) and 6(c). Since the
bootstrap supply current is proportional to the converter
SC4524D
GND
(b)
D
2
load current, using a lower voltage to power the bootstrap
circuit reduces driving loss and improves efficiency.
The bootstrap diode D1 can be a fast switching PN diode
(1N4148 or 1N914) if V O falls between 3V and 8V as shown
in Figure 6(a). If the converter output voltage is between
2.5V and 3V or higher than 8V, then use a low forward drop
V IN
IN
BST
SW
SC4524D
GND
D2
C1
D1
2.5 V < V O < 3V
or V O > 8V
Schottky diode (BAT54 or similar) for D1 (Figure 6(c)). If V O
is less than 2.5V, then it will be necessary to bootstrap the
SC4524D from VIN (Figure 6(b)). D1 is a PN junction diode
(C)
Figure 6 — Methods of Bootstrapping the SC4524D
as in Figure 6(a).
12
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