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PDF NE5561D Data sheet ( Hoja de datos )
| Número de pieza | NE5561D | |
| Descripción | Switched-mode power supply control circuit | |
| Fabricantes | Philipss | |
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Philips Semiconductors
Switched-mode power supply control circuit
Product specification
NE/SE5561
DESCRIPTION
The NE5561/SE5561 is a control circuit for use in switched-mode
power supplies. It contains an internal temperature- compensated
supply, PWM, sawtooth oscillator, overcurrent sense latch, and
output stage. The device is intended for low cost SMPS applications
where extensive housekeeping functions are not required.
FEATURES
• Micro-miniature (D) package
• Pulse-width modulator
• Current limiting (cycle-by-cycle)
• Sawtooth generator
• Stabilized power supply
• Double pulse protection
• Internal temperature-compensated reference
PIN CONFIGURATION
D, FE, N Packages
VCC 1
VZ
FEEDBACK
2
3
GAIN 4
8 GND
7 OUTPUT
6 CURRENT SENSE
5 RT, CT
Figure 1. Pin Configuration
APPLICATIONS
• Switched-mode power supplies
• DC motor controller inverter
• DC/DC converter
ORDERING INFORMATION
DESCRIPTION
8-Pin Plastic Dual In-Line Package (DIP)
8-Pin Plastic Dual In-Line Package (DIP)
8-Pin Ceramic Dual In-Line Package (CERDIP)
8-Pin Small Outline (SO) Package
TEMPERATURE RANGE
0 to +70°C
-55 to +125°C
-55 to +125°C
0 to +70°C
ORDER CODE
NE5561N
SE5561N
SE5561FE
NE5561D
DWG #
SOT97-1
SOT97-1
0580A
SOT96-1
BLOCK DIAGRAM
REF
VOLTAGE
RT, CT
5
SAWTOOTH
GENERATOR
VCC
+
ERROR
AMP
FEEDBACK 3 –
GAIN 4
0.5V
–
6
CURRENT
+
SENSE
PWM
S
LATCH
R
7
OUTPUT
STABILIZED
SUPPLY
8.2V
2 VZ
18
VCC
GND
Figure 2. Block Diagram
SL00385
1994 Aug 31
1 853-0889 13721
1 page  
Philips Semiconductors
Switched-mode power supply control circuit
Product specification
NE/SE5561
NE5561 Voltage-Current-Fed
Supply Characteristics
mA
20
10
0V
0 10 20 30
Current-Fed Dropping Resistor
VS
RVCC
1 VCC
GND
8
VS * VCC
RVCC + (10 20mA)
NOTE:
See DC Electrical Characteristics for Current Fed VCC Range.
SL00387
Figure 4. NE5561 Voltage-Current-Fed Supply Characteristics
NE5561 START-UP
The start-up, or initial turn-on, of this device requires some degree of
external protective duty cycle limiting to prevent the duty cycle from
initially going to the extreme maximum (δ>90%). Either overcurrent
limit or slow-start circuitry must be employed to limit duty cycle to a
safe value during start-up. Both may be used, if desired.
To implement slow-start, the start-up circuit can be used. The divider
R1 and R2 sets a voltage, buffered by Q1, such that the output of
the error amplifier is clamped to a maximum output voltage, thereby
limiting the maximum duty cycle. The addition of capacitor C will
cause this voltage to ramp-up slowly when power is applied, causing
the duty cycle to ramp-up simultaneously.
Overcurrent limit may be used also. To limit duty cycle in this mode,
the switch current is monitored at Pin 6 and the output of the 5561 is
disabled on a cycle-by-cycle basis when current reaches the
programmed limit. With current limit control of slow-start, the duty
cycle is limited to that value, just allowing maximum switch current
to flow. (Approximately 0.50V measured at Pin 6.)
APPLICATIONS
5V, 0.5A Buck Regulator Operates from 15V
The converter design shows how simple it is to derive a TTL supply
from a system supply of 15V (see Figure 1). The NE5561 drives a
2N4920 PNP transistor directly to provide switching current to the
inductor.
Overall line regulation is excellent and covers a range of 12V to 18V
with minimal change (<10mV) in the output operating at full load.
As with all NE5561 circuits, the auxiliary slow start and δMAX circuit
is required, as evidenced by Q1. The δMAX limit may be calculated
by using the relationship:
R1
R2
)
R2
(8.2V)
+
VdMAX
The maximum duty cycle is then determined from the pulse-width
modulator transfer graph, with R1 and R2 being defined from the
desired conditions.
1994 Aug 31
5
5 Page | ||
| Páginas | Total 5 Páginas | |
| PDF Descargar | [ Datasheet NE5561D.PDF ] | |
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