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参数资料
| 型号： | IRDC3637 |
| 厂商： | International Rectifier |
| 文件页数： | 5/21页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL SYNC BUCK REGULATOR |
| 产品变化通告： | (EP) Parts Discontinuation 25/May/2012 |
| 标准包装： | 1 |
| 主要目的： | DC/DC，步降 |
| 输出及类型： | 1，非隔离 |
| 输出电压： | 1.8V |
| 电流 - 输出： | 7A |
| 输入电压： | 4.5 ~ 5.5 V |
| 稳压器拓扑结构： | 降压 |
| 频率 - 开关： | 400kHz |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | IR3637 |
| 产品目录页面： | 1383 (CN2011-ZH PDF) |
| 相关产品： | IR3637ASTRPBFTR-ND - IC REG CTRLR BUCK PWM VM 8-SOIC IR3637ASPBF-ND - IC REG CTRLR BUCK PWM VM 8-SOIC IR3637STRPBFDKR-ND - IC REG CTRLR BUCK PWM VM 8-SOIC IR3637STRPBFCT-ND - IC REG CTRLR BUCK PWM VM 8-SOIC IR3637STRPBFTR-ND - IC REG CTRLR BUCK PWM VM 8-SOIC IR3637SPBF-ND - IC REG CTRLR BUCK PWM VM 8-SOIC |
IR3637SPBF
THEORY OF OPERATION
Soft-Start
The IR3637 has a programmable soft-start to control the
output voltage rise and limit the current surge at the start-
25uA
3V
up. To ensure correct start-up, the soft-start sequence
initiates when the Vc and Vcc rise above their threshold
SS/SD
64uA
Max
HDrv
(3.3V and 4.2V respectively) and generates the Power
On Reset (POR) signal. Soft-start function operates by
POR
sourcing an internal current to charge an external ca-
pacitor to about 3V. Initially, the soft-start function clamps
the E/A’s output of the PWM converter and disables the
short circuit protection. During the power up, the output
starts at zero and voltage at Fb is below 0.4V. The feed-
Comp
0.8V
Fb
25K
25K
Error Amp
LDrv
back UVLO is disabled during this time by injecting a
current (64 μ A) into the Fb. This generates a voltage
about 1.6V (64 μ A × 25K) across the negative input of E/
0.4V
A and positive input of the feedback UVLO comparator
(see Figure 3).
64uA × 25K=1.6V
When SS=0
Feeback
POR
The magnitude of this current is inversely proportional to
the voltage at soft-start pin.
The 20 μ A current source starts to charge up the exter-
nal capacitor. In the mean time, the soft-start voltage
ramps up, the current flowing into Fb pin starts to de-
crease linearly and so does the voltage at the positive
pin of feedback UVLO comparator and the voltage nega-
tive input of E/A.
When the soft-start capacitor is around 1V, the current
flowing into the Fb pin is approximately 32 μ A. The volt-
age at the positive input of the E/A is approximately:
32 μ A × 25K = 0.8V
UVLO Comp
Figure 3 - Soft-start circuit for IR3637.
The output start-up time is the time period when soft-
start capacitor voltage increases from 1V to 2V. The start-
up time will be dependent on the size of the external
soft-start capacitor. The start-up time can be estimated
by:
25 μ A × T START /C SS = 2V-1V
For a given start up time, the soft-start capacitor can be
estimated as:
C SS ? 25 μ A × T START /1V
Output of UVLO
The E/A will start to operate and the output voltage starts
POR
3V
to increase. As the soft-start capacitor voltage contin-
ues to go up, the current flowing into the Fb pin will keep
decreasing. Because the voltage at pin of E/A is regu-
lated to reference voltage 0.8V, the voltage at the Fb is:
V FB = 0.8-25K × (Injected Current)
Soft-Start
Voltage
Current flowing
into Fb pin
0V
64uA
0uA
? 2V
? 1V
The feedback voltage increases linearly as the injecting
current goes down. The injecting current drops to zero
when soft-start voltage is around 2V and the output volt-
age goes into steady state.
Voltage at negative input ? 1.6V
of Error Amp and Feedback
UVLO comparator
0.8V
0.8V
As shown in Figure 4, the positive pin of feedback UVLO
comparator is always higher than 0.4V, therefore, feed-
Voltage at Fb pin
0V
back UVLO is not functional during soft-start.
Figure 4 - Theoretical operational waveforms
during soft-start.
Rev. 1.1
06/16/05
www.irf.com
5
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相关代理商/技术参数 |
参数描述 |
|---|---|
| IRDC3637EVAL | 制造商:IRF 制造商全称:International Rectifier 功能描述:IR3637 EVALUATION BOARD USER GUIDE |
| IRDC3640 | 功能描述:电源管理IC开发工具 IR3640 12V PWM 1.5MHz Controller RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| IRDC3651 | 功能描述:电源管理IC开发工具 IR3651 EVAL BRD 400kHz RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| IRDC3710-DF | 功能描述:电源管理IC开发工具 1 PHASE SYNC-BUCK PWM CTRLLER IC RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| IRDC3710-QFN | 功能描述:电源管理IC开发工具 1 PHASE SYNC-BUCK PWM CTRLLER IC RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
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