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参数资料
| 型号： | FAN4603MM10X |
| 厂商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 0.6 A SWITCHING REGULATOR, 6600 kHz SWITCHING FREQ-MAX, BCC6 |
| 封装： | 4 X 2.50 MM, 1.10 MM HEIGHT, MLP-6 |
| 文件页数： | 12/12页 |
| 文件大小： | 949K |
| 代理商： | FAN4603MM10X |
2009 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN4603 Rev. 1.0.1
9
FAN4603
—
60
0mA,
Fully
Integrat
ed
Buck
Power
Supply
Modul
e
Operation Description
The FAN4603 is a 600mA, step-down, switching-voltage
regulator that delivers a fixed output from an input voltage
supply of 2.3V to 5.5V. Using a proprietary architecture with
synchronous rectification, the FAN4603 is capable of
delivering a peak efficiency of >90%, while maintaining
efficiency over 80% at load currents as low as 1mA. The
regulator operates at a nominal PWM frequency of 6MHz.
Control Scheme
The FAN4603 uses a proprietary, non-linear, fixed-frequency
PWM modulator to deliver a fast load transient response,
while maintaining a constant switching frequency over a
wide range of operating conditions. Regulator stability is not
dependent on output capacitor ESR, which allows the use of
ceramic capacitors. Although this type of operation normally
results in a switching frequency that varies with input voltage
and load current, an internal frequency loop holds the
switching frequency constant over a large range of input
voltages and load currents.
For very light loads, FAN4603 incorporates a discontinuous
current (DCM) single-pulse PFM mode, which produces
lower output ripple when compared with other PFM
architectures. Transition between PWM and PFM is
seamless, with a glitch of less than 20mV at VOUT during the
transition between DCM and CCM modes.
Combined
with
exceptional
transient
response
characteristics, the very low quiescent current of the
controller (35A) maintains high efficiency; even at very light
loads, while preserving fast transient response for
applications requiring tight output regulation.
Enable and Soft-Start
When EN is LOW, all circuits in FAN4603 are off and the IC
draws ~100nA of current. When EN is HIGH and VIN is
above its UVLO threshold, the regulator begins a soft-start
cycle. The output ramp during soft-start is a fixed slew rate
of 50mV/
μs from 0 to 1 VOUT, then 12.5mV/μs until the output
reaches its setpoint.
PWM mode operation is prohibited during the soft-start cycle
to prevent COUT from being discharged. This allows glitchless
starting into a pre-charged output.
Startup into Large COUT
The IC may fail to start if heavy load is applied during startup
and a large external COUT is present. This is due to the
current-limit fault response, which protects the IC in an over-
current condition during soft-start.
The current required to charge COUT during soft-start,
referred to as “displacement current,” is given as:
dt
dV
C
I
OUT
DISP
=
(1)
where
dt
dV
refers to the soft-start slew rate.
To prevent shutdown during soft-start, the following condition
must be met:
)
DC
(
MAX
LOAD
DISP
I
<
+
(2)
where IMAX(DC) is the maximum load current the IC is
guaranteed to support (600mA).
Table 1 shows combinations of external COUT that allow the
IC to start successfully with the minimum RLOAD that can be
supported at each.
Table 1. Minimum
RLOAD
Values
for
Soft-Start
with
Various External COUT Values
COUT
Minimum RLOAD
2.2
μF, 0402
VOUT / 0.55
4.7
μF, 0402
VOUT / 0.50
10
μF, 0603
VOUT / 0.45
Multiple soft-start cycles may be required for COUT>10μf
(15
μf with no load). The IC shuts down for 85μs when IDISP+
ILOAD exceeds ILIMIT for more than 21μs of current limit. The
IC then begins a new soft-start cycle. Subsequent soft-start
cycles begin with any charge retained by COUT while the IC is
off, allowing VOUT to incrementally reach regulation over
multiple soft-start attempts.
Current Limit, Fault Shutdown, and Restart
A heavy load or short circuit on the output causes the current
to increase until a maximum current threshold is reached.
Upon reaching this point, the high-side switch turns off,
preventing high currents from causing damage. The
regulator continues to limit the current cycle-by-cycle. After
21s of current limit, the regulator triggers an over-current
fault, causing the regulator to shut down for about 85
μs
before attempting an automatic restart.
If the fault is caused by short circuit, the soft-start circuit
attempts to restart and produces an over-current fault after
about 32
μs, which results in a duty cycle of less than 30%,
limiting power dissipation.
Under-Voltage Lockout (UVLO)
When EN is HIGH, the under-voltage lockout keeps the part
from operating until the input supply voltage rises high
enough to properly operate. This ensures no misbehavior of
the regulator during startup or shutdown.
Thermal Shutdown
When the die temperature increases, due to a high load
condition and/or a high ambient temperature, the output
switching is disabled until the temperature on the die has
fallen sufficiently. The junction temperature at which the
thermal shutdown activates is nominally 150°C with 15°C
hysteresis. After cooling, the IC automatically restarts, with a
soft-start cycle.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| FAN4603MM12X | 功能描述:直流/直流开关调节器 6MHz, 600mA Sync Buck regulator RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| FAN4603MM13X | 功能描述:直流/直流开关调节器 6MHz, 600mA Sync Buck regulator RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| FAN4603MM15X | 功能描述:直流/直流开关调节器 6MHz, 600mA Sync Buck regulator RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| FAN4603MM18X | 功能描述:开关变换器、稳压器与控制器 6MHz 500mA Sync Buck Regulator RoHS:否 制造商:Texas Instruments 输出电压:1.2 V to 10 V 输出电流:300 mA 输出功率: 输入电压:3 V to 17 V 开关频率:1 MHz 工作温度范围: 安装风格:SMD/SMT 封装 / 箱体:WSON-8 封装:Reel |
| FAN4800 | 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:Low Start-Up Current PFC/PWM Controller Combos |
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