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부품번호 | AME5297 기능 |
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기능 | Step Down DC/DC Converter | ||
제조업체 | AME | ||
로고 | |||
AME
AME5297
3A, 18V, 500KHz Synchronous
Step-Down DC/DC Converter
n General Description
The AME5297 is a high frequency synchronous
stepdown DC-DC converter with built internal power
MOSFETs. That provides wide 4.5V to 18V input voltage
range and 3A continuous load current capability. The
AME5297 has synchronous mode operation for higher
efficiency over output current load range.
The AME5297 is current mode control scheme which
provides fast transient reponse. Internal compensation
function.
n Features
l Wide 4.5V to 18V Operating Input Range
l 80mΩ/30mΩ Low RDS(ON) internal Power
MOSFETs
l Proprietary Switching Loss Reduction Techn
-ique
l High Efficiency Synchronous Mode Operation
l Fixed 500KHz Switching Frequency
l External Programmable Soft Start
l OCP and Hiccup
l Thermal Shutdown
l Output Adjustable from 0.8V
l RoHS Compliant and Halogen Free
n Application
l Notebook Systems and I/O Power
l Digital Set Top Boxes
l LCD Display, TV
l Networking, XDSL Modem
n Typical Application
VIN 4.5-18V
C1
22uF
25V
C3
1uF
C4
22nF
EN
IN BST
VCC
SW
AME5297
SS
EN/SYNC FB
GND
R4
10Ω
C4
0.1uF
L1
4.7uH
R1
40.2K
R3
33K
3.3V 3A
VOUT
C2
47uF
R2
13K
Rev. A.05
1
AME
AME5297
n Ordering Information
3A, 18V, 500KHz Synchronous
Step-Down DC/DC Converter
AME5297 - x x x xxx x
Special Feature
Output Voltage
Number of Pins
Package Type
Pin Configuration
Pin Configuration
A 1. SS
(TSOT-23-8) 2. IN
3. SW
4. GND
5. BST
6. EN
7. VCC
8. FB
Package
Type
Number of
Pins
E: SOT-2X
A: 8
Output Voltage
ADJ: Adjustable
Special Feature
L: TSOT-23-8 (Low Profile)
4 Rev. A.05
4페이지 AME
AME5297
3A, 18V, 500KHz Synchronous
Step-Down DC/DC Converter
n Detailed Descriptiion
Internal VCC Regulator
The internal VCC regulator is adjusted 5.0V to provide
power to the internal circuits from input voltage VIN. In
order to maintain the VCC voltage stably, a 0.1µ F-to-1µF
ceramic capacitor is recommended.
Enable and Soft Start
The EN pin provides electrical on/off control of the regu-
lator. When the EN pin voltage exceeds the lockout thresh-
old voltage, the regulator starts to operate and the soft
start begins to charge the external capacitor. If the EN pin
voltage is pulled below the lockout threshold voltage, the
regulator stops switching and the soft start resets. Con-
necting the EN pin to ground or to any voltage less than
1.2V will disable the regulator and activate the shutdown
mode. To limit the start-up inrush current, a soft-start
circuit is used to ramp up the reference voltage from 0V to
its final value linearly. The soft start time can be calcu-
lated as follows:
t SS
=
0.8× CSS
ISS
Under Voltage Lockout (UVLO)
The AME5297 incorporates an under voltage lockout cir-
cuit to keep the device disabled when the input voltage
VIN is below the UVLO start threshold voltage. During
powering up, the internal circuits are held inactive and the
soft start is grounded until the input voltage VIN exceeds
the UVLO start threshold voltage. Once the UVLO start
threshold voltage is reached, the soft start is activated and
the device begins to operate. The device operates until
the input voltage VIN falls below the UVLO stop threshold
voltage. The typical hysteresis in the UVLO comparator
is 650mV.
Rev. A.05
Thermal Shutdown
The AME5297 protects itself from overheating with an
internal thermal shutdown circuit. If the junction tempera-
ture exceeds the thermal shutdown threshold, the voltage
reference is grounded and the shutdown mode is activated.
The AME5297 is restarted under control of the soft start
automatically when the junction temperature drops 20oC
below the thermal shutdown threshold.
Over-Current Protection and Hiccup Mode
The over-current limiting is implemented by cycle-by-
cycle monitoring the current through the high side MOSFET.
If the peak current exceeds the over-current limit thresh-
old, the high side MOSFET is turned off. When the feed-
back voltage VFB drops below 0.4V, the oscillator frequency
is reduced to about 1/4 of the normal frequency to ensure
that the inductor current has more time to decay, thereby
preventing runaway. Meanwhile, the AME5297 enters hic-
cup mode, the average short circuit current is greatly re-
duced to alleviate the thermal issue and to protect the
regulator.
Enternal Bootstrap Circuit
The external bootstrap circuit contains a capacitor and a
resistor. A bootstrap capacitor provides power for the high
side MOSFET driver. In order to supply the AC current and
maintain the BST-SW voltage stably at the switching con-
dition of the high side MOSFET, a 0.1µF low ESR ceramic
capacitor is recommended. The bootstrap resistor which
suggests placing 10Ω is utilized to reduce switching spike
voltage and noise.
7
7페이지 | |||
구 성 | 총 14 페이지수 | ||
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DataSheet.kr | 2020 | 연락처 | 링크모음 | 검색 | 사이트맵 |