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PDF AP1623 Data sheet ( Hoja de datos )
| Número de pieza | AP1623 | |
| Descripción | PWM Control Step-Down Switching Regulator-Converter | |
| Fabricantes | Anachip | |
| Logotipo |  |
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PWM Control Step-Down Switching Regulator-Converter
AP1623
Features
- Low current consumption:
In operation: 60µA max.
Power off: 0.5µA max.
- Input voltage: 2.5V to 16V.
- Output voltage: 1.8V & Adjustable to 6V.
- Duty ratio: 0% to 100% PWM control
- Oscillation frequency: 180KHz typ.
- Soft-start function: 8ms typ.
- With a power-off function.
- Built-in internal SW P-channel MOS
- SOP-8L Package.
Applications
- On-board power supplies of battery devices for
portable telephones, electronic notebooks, PDA,
and other hand-held sets.
- Power supplies for audio equipment, including
portable CD players and headphone stereo
equipment.
- Fixed voltage power supply for cameras, video
equipment and communications equipment.
- Power supplies for microcomputers.
- Conversion from four Ni-H or Ni-Cd cells or two
lithium-ion cells to 3.3V/3V.
- Conversion of AC adapter input to 5V/3V.
General Description
AP1623 consists of CMOS step-down switching
regulator-controllers with PWM control. These devices
include a reference voltage source, oscillation circuit,
error amplifier, internal PMOS and etc.
AP1623 provides low-ripple power, high efficiency,
and excellent transient characteristics. The PWM
control circuit is able to very the duty ratio linearly
from 0 up to 100. This converter also contains an
error amplifier circuit as well as a soft-start circuit that
prevent s overshoot at startup.
With the addition of an internal P-channel Power MOS,
a coil, capacitors, and a diode connected externally,
these ICs can function as step-down switching
regulators. They serve as ideal power supply units for
portable devices when coupled with the SOP–8L
mini-package, providing such outstanding features as
low current consumption. Since this converter can
accommodate an input voltage of up to 16V, it is also
ideal when operating via an AC adapter.
Pin Assignments
VOUT 1
ON/OFF 2
VCC 3
PVCC 4
AP1623
8 Vss
7 Vss
6 SW
5 SW
Pin Descriptions
Name Pin
Description
VOUT
ON/OFF
1 Output voltage monitoring pin
Power-off pin
H: Normal operation
2
(Step-down operation)
L: Step-down operation
stopped
(All circuits deactivated)
VCC 3 IC signal power supply pin
PVCC
SW
VSS
4 IC power supply pin
Switch Pin. Connect external
5、6
inductor/diode here. Minimize
trace area at this pin to reduce
EMI.
7、8 GND Pin
This datasheet contains new product information. Anachip Corp. reserves the rights to modify the product specification without notice. No liability is assumed as a result of the use of
this product. No rights under any patent accompany the sale of the product.
Rev. 0.1 Feb 10, 2004
1/6
1 page  
PWM Control Step-Down Switching Regulator-Controllers
AP1623
Function Description
PWM Control (AP1623 Series)
The AP1623 consists of DC/DC converters that
employ a pulse-width modulation (PWM) system.
In converters of the AP1623, the pulse width varies
in a range from 0 to 100, according to the load
current, and yet ripple voltage produced by the
switching can easily be removed through a filter
because the switching frequency remains constant.
Therefore, these converters provide a low-ripple
power over broad ranges of input voltage and load
current.
External adjustment of output voltage
The AP1623 allows the user to select 3 types of the
output voltage, when external resistances RA, RB,
and capacitor CC are added, as illustrated in Typical
Application Circuit. Moreover, a temperature
gradient can be obtained by inserting a
thermal-resistor or other element in series with RA
and RB.
Therefore, the output voltage (OUT) is determined
by the output voltage value VOUT of the AP1623,
and the ratio of the parallel resistance value of
external resistance RB and internal resistance R1 +
R2 of the IC, to external resistance RA. The output
voltage is expressed by the following equation:
OUT = VOUT + VOUT × RA ÷ (RB // (R1+ R2))
(Note:// denotes a combined resistance in parallel.)
The voltage accuracy of the output OUT set by
resistances RA and RB is not only affected by the
IC’s output voltage accuracy (VOUT ± 2.4%), but also
by the absolute precision of external resistances RA
and RB in use and the absolute value deviations of
internal resistances R1 and R2 in the IC.
Let us designate the maximum deviations of the
absolute value of external resistances RA and RB by
RAmax and RBmax, respectively, the minimum
deviations by RAmin and RBmin, respectively, and
the maximum and minimum deviations of the
absolute value of internal resistances R1 and R2 in
the IC by (R1+ R2)max and (R1+ R2)min,
respectively. Then, the minimum deviation value
OUTmin and the maximum deviation value
OUTmax of the output voltage OUT are expressed
by the following equations:
OUTmin = VOUT × 0.976 + VOUT × 0.976 × RAmin ÷
(RBmax// (R1+ R2)max)
OUTmax = VOUT × 1.024 + VOUT × 1.024 × RAmax ÷
(RBmin// (R1+ R2)min)
The voltage accuracy of the output OUT cannot be
made higher than the output voltage accuracy (VOUT
± 2.4%) of the IC itself, without adjusting the
external resistances RA and RB involved. The closer
the voltage value of the output OUT and the output
voltage value (VOUT) of the IC are brought to one
other, the more the output voltage remains immune
to deviations in the absolute accuracy of externally
connected resistances RA and RB and the absolute
value of internal resistances R1 and R2 in the IC.
In particular, to suppress the influence of deviations
in internal resistances R1 and R2 in the IC, a major
contributor to deviations in the output OUT, the
external resistances RA and RB must be limited to a
much smaller value than that of internal resistances
R1 and R2 in the IC.
On the other hand, a reactive current flows through
external resistances RA and RB. This reactive
current must be reduced to a negligible value with
respect to the load current in the actual use of the
IC so that the efficiency characteristics will not be
degraded. This requires that the value of external
resistance RA and RB be made sufficiently large.
However, too large a value (more than 1 MΩ) for
the external resistances RA and RB would make the
IC vulnerable to external noise. Check the influence
of this value on actual equipment.
There is a tradeoff between the voltage accuracy of
the output OUT and the reactive current. This
should be taken into consideration based on the
requirements of the intended application.
Deviations in the absolute value of internal
resistances R1 and R2 in the IC vary with the
output voltage of the AP1623, and are broadly
classified as follows:
. Output voltage 2.5V → 4.44MΩ to 27.0MΩ
. Output voltage 3.3V → 3.60MΩ to 23.3MΩ
. Output voltage 5.0V → 2.45MΩ to 2.45MΩ
When a value of R1+R2 given by the equation
indicated below is taken in calculating the voltage
value of the output OUT, a median voltage deviation
will be obtained for the output OUT.
R1 + R2 = 2 ÷ ( 1 ÷ maximum deviation in absolute
value of internal resistances R1 and R2 in IC + 1 ÷
minimum deviation in absolute value of internal
resistances R1 and R2 of IC)
Moreover, add a capacitor CC in parallel to the
external resistance RA in order to avoid output
oscillations and other types of instability.
Make sure that CC is larger than the value given by
the following equation:
CC(F)≥1÷ (2 ×π × RA (Ω) × 7.5kHz)
If a large CC-value is selected, a longer soft-start
time than the one set up in the IC will be set.
Anachip Corp.
www.anachip.com.tw
Rev. 0.1 Feb 10, 2004
5/6
5 Page | ||
| Páginas | Total 6 Páginas | |
| PDF Descargar | [ Datasheet AP1623.PDF ] | |
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