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PDF DPA423 Data sheet ( Hoja de datos )
| Número de pieza | DPA423 | |
| Descripción | (DPA423 - DPA426) Highly Integrated DC-DC Converter ICs for Distributed Power Architectures | |
| Fabricantes | Power Integrations | |
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DPA423-426
DPA-Switch™ Family
Highly Integrated DC-DC Converter ICs
for Distributed Power Architectures
Product Highlights
Highly Integrated Solution
• Eliminates 20-50 external components–saves space, cost
• Integrates 220 V high frequency MOSFET, PWM control
• Lower cost plastic DIP surface mount (G package) and
through-hole (P package) options for designs ≤35 W
Superior Performance and Flexibility
• Eliminates all external current sensing circuitry
• Built-in auto-restart for output overload/open loop protection
• Pin selectable 300/400 kHz fixed frequency
• Wide input (line) voltage range: 16-75 VDC
• Source connected tab reduces EMI
• Line under-voltage (UV) detection: meets ETSI standards
• Line overvoltage (OV) shutdown protection
• Low cost synchronous rectification: line UV/OV shut down
limits gate drive voltage range from transformer winding
• Fully integrated soft-start for minimum stress/overshoot
• Externally programmable current limit
• Supports forward or flyback topology
• Cycle skipping: regulation to zero load without pre-load
• Hysteretic thermal shutdown for automatic fault recovery
EcoSmart ®- Energy Efficient
• Extremely low consumption at no load
• Cycle skipping at light load for high standby efficiency
Applications
• Telco central office equipment: xDSL, ISDN, PABX, etc.
• Distributed power architectures (24 V/48 V bus, etc.)
• Digital feature phones, VoIP phones, PoE
• Industrial controls (24 V/48 V)
Description
The DPA-Switch IC family introduces a highly integrated
solution for DC-DC conversion applications in the 16-75 VDC
input range.
DPA-Switch uses the same proven topology as TOPSwitch, cost
effectively integrating the high voltage power MOSFET, PWM
control, fault protection and other control circuitry onto a single
CMOS chip. High performance features are enabled with three
user configurable pins.
DPA-Switch
VIN D
RESET/
CLAMP
CIRCUIT
S
L
CONTROL
C
XF
VO
SENSE
CIRCUIT
Figure 1. Typical Forward Converter Application.
PI-2770-032002
OUTPUT POWER TABLE
36-75 VDC INPUT RANGE (FORWARD)2,4
Total Device
Dissipation3 0.5 W 1 W 2.5 W 4 W
PRODUCT4
Max
6 W Power
Output1
DPA423 12 W 16 W - - - 18 W
DPA424 16 W 23 W 35 W - - 35 W
DPA425 23 W 32 W 50 W 62 W - 70 W
DPA426 25 W 35 W 55 W 70 W 83 W 100 W
36-75 VDC INPUT RANGE (FLYBACK)2
Total Device3
Dissipation 0.5 W
PRODUCT4
0.75 W
1W
Max
1.5 W Power
Output1
DPA423 9 W 13 W -
- 13 W
DPA424 10 W 14.5 W 18 W 24 W 26 W
DPA425
-5
-5
-5 25.5 W 52 W
Table 1. Notes: 1. Maximum output power is limited by device internal
current limit. 2. See Applications Considerations section for complete
description of assumptions and for output powers with other input voltage
ranges. 3. For device dissipation of 1.5 W or below, use P or G packages.
Device dissipation above 1.5 W is possible only with R package. 4. See
Part Ordering Information. 5. Due to higher switching losses, the DPA425
may not deliver additional power compared to a smaller device.
The following transparent or built-in features are also provided:
soft-start, cycle skipping down to zero load and hysteretic
thermal shutdown. In addition, all critical parameters (i.e.
current limit, frequency, PWM gain) have tight temperature
and absolute tolerance, to simplify design and optimize system
cost.
January 2004
1 page  
approximately 5.8 V, the control circuitry is activated and the
soft-start begins. The soft-start circuit gradually increases the
duty cycle of the MOSFET from zero to the maximum value
over approximately 5 ms. The high voltage current source is
turned off at the end of the soft-start. If no external feedback/
supply current is fed into the CONTROL pin by the end of the
soft-start, the CONTROL pin will start discharging in response
to the supply current drawn by the control circuitry and the gate
current of the switching MOSFET driver. If the power supply
is designed properly, and no fault condition such as open loop
or overloaded output exists, the feedback loop will close,
providing external CONTROL pin current, before the
CONTROL pin voltage has had a chance to discharge to the
lower threshold voltage of approximately 4.8 V (internal supply
under-voltage lockout threshold). When the externally fed
current charges the CONTROL pin to the shunt regulator
voltage of 5.8 V, current in excess of the consumption of the
chip is shunted to SOURCE through resistor RE as shown in
Figure 2. This current flowing through RE controls the duty
cycle of the power MOSFET to provide closed loop regulation.
The shunt regulator has a finite low output impedance ZC that
sets the gain of the error amplifier when used in a primary
feedback configuration. The dynamic impedance ZC of the
CONTROL pin together with the external CONTROL pin
capacitance sets the dominant pole for the control loop.
When a fault condition such as an open loop or overloaded
output prevents the flow of an external current into the
CONTROL pin, the capacitor on the CONTROL pin discharges
towards 4.8 V. At 4.8 V auto-restart is activated which turns the
output MOSFET off and puts the control circuitry in a low
DPA423-426
current standby mode. The high-voltage current source turns on
and charges the external capacitance again. A hysteretic
internal supply under-voltage comparator keeps VC within a
window of typically 4.8 to 5.8 V by turning the high-voltage
current source on and off as shown in Figure 5. The auto-restart
circuit has a divide-by-8 counter that prevents the output
MOSFET from turning on again until eight discharge/charge
cycles have elapsed. This is accomplished by enabling the
output MOSFET only when the divide-by-8 counter reaches
full count (S7). The counter effectively limits DPA-Switch
power dissipation as well as the maximum power delivered to
the power supply output by reducing the auto-restart duty cycle
to typically 4%. Auto-restart mode continues until output
voltage regulation is again achieved through closure of the
feedback loop.
Oscillator and Switching Frequency
The internal oscillator linearly charges and discharges an internal
capacitance between two voltage levels to create a sawtooth
waveform for the pulse width modulator. The oscillator sets
both the pulse width modulator latch and the current limit latch
at the beginning of each cycle.
The nominal switching frequency of 400 kHz was chosen to
minimize the transformer size and to allow faster power supply
loop response. The FREQUENCY pin, when shorted to the
CONTROL pin, lowers the switching frequency to 300 kHz,
which may be preferable in some applications such as those
employing secondary synchronous rectification. Otherwise,
the FREQUENCY pin should be connected to the SOURCE pin
for the default 400 kHz.
VLINE
0V
VUV
VC
0V
VDRAIN
0V
S7 S0
S1 S2
S6 S7 S0 S1 S2
S6 S7
S0
S1 S2
S6 S7 S7
5.8 V
4.8 V
VOUT
0V
12
3
Note: S0 through S7 are the output states of the auto-restart counter
2
Figure 5. Typical Waveforms for (1) Power Up (2) Normal Operation (3) Auto-restart (4) Power Down.
4
PI-2545-050602
5K
1/04
5 Page 
DPA423-426
CONTROL Pin
230 µA
DPA-Switch
EXTERNAL CURRENT LIMIT (X)
(Negative Current Sense - ON/OFF,
Current Limit Adjustment)
VBG + VT
LINE-SENSE (L)
(Voltage Sense)
VBG 1 V
(Positive Current Sense - Under-Voltage,
Overvoltage, ON/OFF Maximum Duty
Cycle Reduction)
240 µA
Figure 8. LINE-SENSE (L), and EXTERNAL CURRENT LIMIT (X) Pin Input Simplified Schematic.
PI-2765-080801
11K
1/04
11 Page | ||
| Páginas | Total 36 Páginas | |
| PDF Descargar | [ Datasheet DPA423.PDF ] | |
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