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PDF APW7237 Data sheet ( Hoja de datos )
| Número de pieza | APW7237 | |
| Descripción | Step-Up Converter | |
| Fabricantes | ANPEC | |
| Logotipo |  |
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APW7237
1.5MHz, High Efficiency, Step-Up Converter with Internal FET Switch
Features
General Description
• Wide 2.7V to 6V Input Voltage Range
The APW7237 is a fixed switching frequency (1.5MHz
• Built-in 0.2Ω N-Channel MOSFET
• Built-in Soft-Start
• High Efficiency up to 90%
• <1µA Quiescent Current During Shutdown
• Current-Mode Operation
- Stable with Ceramic Output Capacitors
- Fast Transient Response
• Current-Limit Protection
typical), current-mode, step-up regulator with an inte-
grated N-channel MOSFET. The device allows the usage
of small inductors and output capacitors for portable
devices. The current-mode control scheme provides fast
transient response and good output voltage accuracy.
The APW7237 includes under-voltage lockout, current-
limit, and over-temperature shutdown preventing dam-
age in the event of an output overload.
• Over-Temperature Protection with Hysteresis
100
• Available in a TSOT-23-5A and TDFN2x2-6 Pack-
age 80
• Lead Free and Green Devices Available
(RoHS Compliant)
60 VIN=3.3V
Applications
40 VIN=5V
• Cell Phone and Smart Phone
• PDA, PMP, MP3
• Digital Camera
• Boost Regulators
20
0
0.01
VOUT=12V
0.1
Supply Voltage (V)
1
Pin Configuration
Simplified Application Circuit
LX 1
GND 2
FB 3
5 VIN
4 EN
TSOT-23-5A
Top View
VIN 1
GND 2
EN 3
6 LX
5 GND
4 FB
TDFN2x2-6
Top View
VIN
5V
C1
4.7µF
ON
OFF
L1
10µH
VIN LX
GND
APW7237
EN FB
VOUT
R1
1.2MΩ
12V
C2
4.7µF
R2
137kΩ
ANPEC reserves the right to make changes to improve reliability or manufacturability without notice, and
advise customers to obtain the latest version of relevant information to verify before placing orders.
Copyright © ANPEC Electronics Corp.
Rev. A.2 - Dec., 2012
1
www.anpec.com.tw
1 page  
APW7237
Typical Operating Characteristics
Output Current vs. Efficiency, VOUT=5V
100
VIN=4.2V
80
VIN=3.3V
60
40
20
0
0.01
0.1
Output Current (A)
1
Supply Voltage vs. IVIN Current
8
6
4
2
0
2.5
0.5
Switching
3 3.5 4 4.5 5 5.5 6
Supply Voltage (V)
Supply Voltage vs. Switch ON
Resistance
0.4
0.3
0.2
0.1
0
2 2.5 3 3.5 4 4.5 5 5.5 6
Supply Voltage (V)
Copyright © ANPEC Electronics Corp.
Rev. A.2 - Dec., 2012
5
Output Current vs. Efficiency, VOUT=12V
100
80
60 VIN=3.3V
40 VIN=5V
20
0
0.01
VOUT=12V
0.1
Output Current (A)
1
Supply Voltage vs. IVIN Current
250
200
150
100
50
No Switching
0
2.5 3 3.5 4 4.5 5 5.5 6
Supply Voltage (V)
Supply Voltage vs. Maximum Duty
Cycle
100
80
60
40
2.5 3 3.5 4 4.5 5 5.5 6
Supply Voltage (V)
www.anpec.com.tw
5 Page 
APW7237
Function Description
Main Control Loop
The APW7237 is a constant frequency and current-mode
switching regulator. In normal operation, the internal N-
channel power MOSFET is turned on each cycle when the
oscillator sets an internal RS latch, and then turned off
when an internal comparator (ICMP) resets the latch. The
peak inductor current at which ICMP resets the RS latch
is controlled by the voltage on the COMP node which is
the output of the error amplifier (EAMP). An external resis-
tive divider connected between VOUT and ground allows
the EAMP to receive an output feedback voltage V at FB
FB
pin. When the load current increases, it causes a slightly
to decrease in VFB associated with the 1.23V reference,
which in turn, it causes the COMP voltage to increase
until the average inductor current matches the new load
current.
VIN Under-Voltage Lockout (UVLO)
The Under-Voltage Lockout (UVLO) circuit compares the
input voltage at VIN with the UVLO threshold to ensure
the input voltage is high enough for reliable operation.
The 100mV (typ) hysteresis prevents supply transients
from causing a restart. Once the input voltage exceeds
the UVLO rising threshold, startup begins. When the in-
put voltage falls below the UVLO falling threshold, the
controller turns off the converter.
Soft-Start
The APW7237 has a built-in soft-start to control the output
voltage rise during start-up. During soft-start, an internal
ramp voltage, connected to the one of the positive inputs
of the error amplifier, raises up to replace the reference
voltage (1.23V typical) until the ramp voltage reaches the
reference voltage.
Current-Limit Protection
The APW7237 monitors the inductor current, flows through
the N-channel MOSFET, and limits the current peak at
current-limit level to prevent loads and the APW7237 from
damaging during overload or short-circuit conditions.
Over-Temperature Protection (OTP)
The over-temperature circuit limits the junction tempera-
ture of the APW7237. When the junction temperature ex-
ceeds 150oC, a thermal sensor turns off the power
MOSFET allowing the devices to cool. The thermal sen-
sor allows the converters to start a soft-start process and
regulates the output voltage again after the junction tem-
perature cools by 40oC. The OTP is designed with a 40oC
hysteresis to lower the average Junction Temperature
(TJ) during continuous thermal overload conditions in-
creasing the lifetime of the device.
Enable/Shutdown
Driving EN to the ground places the APW7237 in shut-
down mode. When in shutdown, the internal power
MOSFET turns off, all internal circuitry shuts down, and
the quiescent supply current reduces to 1µA maximum.
Copyright © ANPEC Electronics Corp.
Rev. A.2 - Dec., 2012
11
www.anpec.com.tw
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet APW7237.PDF ] | |
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