概述
数据手册ML4863ES 概述
High Efficiency Flyback Controller 高效率反激式控制器
ML4863ES 数据手册
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PDF下载July 2000
FEATURING
Extended Commercial Temperature Range
-20˚C to 70˚C
ML4863*
for Portable Handheld Equipment
High Efficiency Flyback Controller
GENERAL DESCRIPTION
FEATURES
The ML4863 is a flyback controller designed for use in
multi-cell battery powered systems such as PDAs and
notebook computers. The flyback topology is ideal for
systems where the battery voltage can be either above or
below the output voltage, and where multiple output
voltages are required.
■ Variable frequency current mode control and
synchronous rectification for high efficiency
■ Minimum external components
■ Guaranteed start-up and operation over a wide input
voltage range (3.15V to 15V)
The ML4863 uses the output voltage as the feedback
control signal to the current mode variable frequency
flyback controller. In addition, a synchronous rectifier
control output is supplied to provide the highest possible
conversion efficiency (greater than 85% efficiency over a
1mA to 1A load range).
■ High frequency operation (>200kHz) minimizes the
size of the magnetics
■ Flyback topology allows multiple outputs in addition to
the regulated 5V
The ML4863 has been designed to operate with a
minimum number of external components to optimize
space and cost.
■ Built-in overvoltage and current limit protection
*Some Packages Are Obsolete
BLOCK DIAGRAM
V
SHDN
CC
3
BIAS & UVLO
V
FB
V
CC
V
5
IN
4.5V
LDO
1
4
V
FB
–
V
FB
+
V
REF
GND
I
8
6
V
CC
CURRENT
COMPARATOR
OUT 1
+
SWITCHING
CONTROL
A1
COMP
–
18mV
18mV
R
CROSS-CONDUCTION
PROTECTION
gm
V
CC
RECTIFIER
COMPARATOR
OUT 2
–
COMP
A2
7
2
BLANKING
+
SENSE
1
ML4863
PIN CONFIGURATION
ML4863
8-Pin SOIC (S08)
V
1
2
3
4
8
7
6
5
GND
IN
SENSE
SHDN
OUT 2
OUT 1
V
V
CC
FB
TOP VIEW
PIN DESCRIPTION
PIN NAME
FUNCTION
PIN NAME
FUNCTION
1
2
3
V
Battery input voltage
Secondary side current sense
5
6
7
8
V
Internal power supply node for
connection of a bypass capacitor
IN
CC
SENSE
SHDN
OUT 1
OUT 2
GND
Flyback primary switch MOSFET driver
output
Pulling this pin high initiates a
shutdown mode to minimize battery
drain
Flyback synchronous rectifier MOSFET
driver output
4
V
Feedback input from transformer
FB
secondary, and supply voltage when
Analog signal ground
V
> 4.5V
OUT
2
ML4863
ABSOLUTE MAXIMUM RATINGS
Absolute maximum ratings are those values beyond which
the device could be permanently damaged. Absolute
maximum ratings are stress ratings only and functional
device operation is not implied.
Lead Temperature (Soldering 10 Sec.) ..................... 260ºC
Thermal Resistance (q ) .................................... 160ºC/W
JA
OPERATING CONDITIONS
V
................................................................. GND – 0.3V to 18V
Temperature Range
IN
Voltage on any other pin ........................... GND – 0.3V to 7V
Source or Sink Current (OUT1 & OUT2)...................... 1A
Junction Temperature ..............................................150ºC
Storage Temperature Range...................... –65ºC to 150ºC
ML4863CS................................................. 0ºC to 70ºC
ML4863ES ............................................. –20ºC to 70ºC
ML4863IS .............................................. –40ºC to 85ºC
V
Operating Range ...................................3.15V to 15V
IN
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, V = 12V, T = Operating Temperature Range (Note 1)
IN
A
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
OSCILLATOR
tON
ON Time
C Suffix
2.1
2.1
2.5
2.5
2.8
2.95
850
µs
µs
ns
E/I Suffix
Minimum Off Time
VFB REGULATION
Total Variation
OUTPUT DRIVERS
OUT1 Rise Time
VFB = 0V
450
650
Line, Load, & Temp
4.85
5
5.15
V
CLOAD = 3nF, 20% to 90% of VCC
CLOAD = 3nF, 90% to 20% of VCC
CLOAD = 3nF, 20% to 90% of VCC
60
60
60
70
70
70
ns
ns
ns
OUT1 Fall Time
OUT2 Rise Time
OUT2 Fall Time
Continuous Mode, CLOAD = 3nF,
90% to 20% of VCC
60
70
ns
ns
Discontinuous Mode, CLOAD = 3nF,
90% to 20% of VCC
125
150
SHDN
SENSE
Input High Voltage
Input Low Voltage
Input Bias Current
2.0
V
V
0.8
10
SHDN = 5V
5
µA
SENSE Threshold – Full Load
VIN = 5V, VFB = VFB (No Load) – 100mV
VFB = 0V
130
150
160
235
mV
mV
SENSE Threshold – Short Circuit
CIRCUIT PROTECTION
Undervoltage Lockout Start-up Threshold
Undervoltage Lockout Hysteresis
3.0
0.5
3.15
0.6
V
V
3
ML4863
ELECTRICAL CHARACTERISTICS (Continued)
SYMBOL
SUPPLY
IFB
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
VFB Quiescent Current
100
20
5
150
25
µA
µA
µA
V
IIN
VIN Shutdown Current
SHDN = 5V
SHDN = 5V, VIN < 6V
10
VCC
VCC Output Voltage
VFB = 0V, VIN = 15V, CVCC = 0.1µF
VFB = 0V, VIN = 6V, CVCC = 0.1µF
VFB = 0V, VIN = 3.15V, CVCC = 0.1µF
VFB = 5V
4.5
4.0
2.8
4.5
5.5
5.0
V
V
5
5.15
V
Note 1: Limits are guaranteed by 100% testing, sampling, or correlation with worst case test conditions.
4
ML4863
FUNCTIONAL DESCRIPTION
The ML4863 utilizes a flyback topology with constant on-
time control. The circuit determines the length of the off-
time by waiting for the inductor current to drop to a level
TRANSCONDUCTANCE AMPLIFIER
The feedback transconductance amplifier generates a
current from the voltage difference between the output
and the reference. This current produces a voltage across
determined by the feedback voltage (V ). Consequently,
FB
the current programming is somewhat unconventional
because the valley of the current ripple is programmed
instead of the peak. The controller automatically enters
burst mode when the programmed current falls below
zero. Constant on-time control therefore features a
transition into and out of burst mode which does not
require additional control circuitry.
R
that adds to the negative voltage on the current sense
gm
resistor, R
. When the current level in the inductor
SENSE
drops low enough to cause the voltage at the non-inverting
input of the current programming comparator to go
positive, the comparator trips and the converter starts a
new on-cycle. The current programming comparator
controls the length of the off-time by waiting until the
current in the secondary decreases to the value specified
by the feedback transconductance amplifier.
The control circuit is made up of four distinctive blocks;
the constant on-time oscillator, the current programming
comparator, the feedback transconductance amplifier, and
the synchronous rectifier controller. A simplified circuit
diagram is shown in Figure 1.
In this way, the feedback transconductance amplifier‘s
output current steers the current level in the inductor.
When the output voltage drops due to a load increase, it
will increase the output current of the feedback amplifier
OSCILLATOR & COMPARATOR
and generate a larger voltage across R which in turn
gm
The oscillator has a constant on-time and a minimum off-
time. The off-time is extended as long as the output of the
current programming comparator is low. Note that in
constant on-time control, a discharge (off-time) cycle is
needed for the inductor current to be sensed. The
minimum off-time is required to account for the finite
circuit delays in sensing the inductor output current.
raises the secondary current trip level. However, when the
output voltage is too high, the feedback amplifier’s output
current will eventually become negative. Because the
output current of the inductor can never go negative by
virtue of the diode, the non-inverting input of the
comparator will also stay negative. This causes the
converter to stop operation until the output voltage drops
enough to increase the output current of the feedback
transconductance amplifier above zero.
V
OUT
I
S
V
IN
R
ESR
4
V
FB
L
P
1:1
FEEDBACK
TRANSCONDUCTANCE
AMPLIFIER
CONSTANT ON-TIME
MINIMUM OFF-TIME
OSCILLATOR
CURRENT
PROGRAMMING
COMPARATOR
R
P
C
+
ONE SHOT
+
OUT 1
–
COMP
–
t
V
ON
REF
6
C
2.5µs
P
ONE SHOT
t
OFF
500ns
R
gm
RECTIFIER
COMPARATOR
OUT 2
SENSE
–
COMP
+
BLANKING
7
2
A2
ML4863
R
SENSE
Figure 1. Schematic of the ML4863 Controller and Power Stage
5
ML4863
FUNCTIONAL DESCRIPTION (Continued)
SYNCHRONOUS RECTIFIER CONTROL
where h = converter efficiency.
Once R has been determined, L can be found:
The control circuitry for the synchronous rectifier does not
influence the operation of the main controller. The
synchronous rectifier is turned on during the minimum off
time, or whenever the SENSE pin is less than –18mV.
During transitions where the primary switch is turned on
before the voltage on the SENSE pin goes above –18mV,
the gate of the synchronous rectifier is discharged softly to
avoid accidently triggering the current-mode comparator
with the gate discharge spike on the sense resistor.
SENSE
P
LP = (25×10−6 ) × V
×RSENSE
(2)
IN MAX
0 5
Three operational modes are defined by the voltage at the
SENSE pin at the end of the off-time: discontinuous mode,
continuous mode, and current limit. The following values
can be used to determine the current levels of each mode:
V
< 0V: discontinuous mode
SENSE
The part will also operate with a Schottky diode in place
of the synchronous rectifier, but the conversion efficiency
will suffer.
0V < V
< 160mV: continuous mode
SENSE
160mV < V
< 235mV: current limit
SENSE
CURRENT LIMIT AND MODES OF OPERATION
Inserting the maximum value of V
for each
SENSE
The normal operating range and current limit point are
determined by the current programming comparator. They
are dependent on the value of the synchronous rectifier
operational mode into the following equation will
determine the maximum current levels for each
operational mode:
current sense resistor (R
), the nominal transformer
SENSE
ꢀ
IN ꢃ
× η
V
VSENSE
tON × V
primary inductance (L ), and the input voltage.
IN
P
IOUT
=
×
+
ꢂR
ꢅ
(3)
VOUT + V
2×LP
ꢁ
ꢄ
IN
SENSE
R
can be calculated by:
SENSE
ꢀ
ꢁ
ꢃ
V
V
ꢂ 150mV
5ꢅꢄ
IN
0
MIN
5
IN
0
MIN
5
RSENSE
(1)
VOUT
V
IOUT
20
V
IOUT
IN
0
MAX
5
IN
0
MAX
5
0
MAX
6
ML4863
DESIGN CONSIDERATIONS
DESIGN PROCEDURE
See Table 1 for suggested component manufacturers.
Part
Number
A typical design can be implemented by using the
following procedure.
Component Manufacturer
Phone
Sense
Resistors
Dale
IRC
LRC Series
WSL Series
(402) 563-6506
(512) 992-7900
1.
Specify the application by defining:
Inductors
Coilcraft
Coiltronics
Dale
R4999
(847) 639-6400
The maximum input voltage (V
)
IN(MAX)
The mainimum input voltage (V
)
OCTA-PAC Series (561)241-7876
IN(MIN)
OUT(MAX)
The maximum output current (I
The maximum output ripple (DV
)
LPE-6562 Series (605) 665-9301
LPT-4545 series
)
OUT
Capacitors AVX
Sprague
TPS series
(207) 282-5111
(207) 324-4140
As a general design rule, the output ripple should be kept
below 100mV to ensure stability.
593D Series
MOSFETs National
NDS94XX
NDS99XX
(800) 272-9954
2.
Select a sense resistor, R
, using equation 1.
SENSE
Motorola
MMDF Series
MMSF Series
(602) 897-5056
3a.
Determine the inductance required for the
optimum output ripple using equation 2.
Siliconix
Littlefoot Series (408) 988-8000
3b.
3c.
Determine the minimum inductor current rating
required. The peak inductor current is calculated
using the following formula:
Table 1. Component Suppliers
6
V
(2.5 10
)
235mV
RSENSE
IN (MAX)
DESIGN EXAMPLE
IL PEAK
=
+
(4)
LP
1.
Specify the application by defining:
Specify the inductor's DC winding resistance. A
good rule of thumb is to allow 5mW, or less, of
resistance per µH of inductance. For minimum
core loss, choose a high frequency core material
such as Kool-Mu, ferrite, or MPP.
V
V
= 6V
= 4V
IN(MAX)
IN(MIN)
I
= 500mA
OUT(MAX)
DV
= 100mV
OUT
2.
Select the sense resistor, R
, using Equation 1:
SENSE
3d.
4a.
Specify the coupled inductor's turns ratio:
Np : Ns = 1:1
4
5+ 4
150mV
ꢁ500mA 20 × 6 × 0.5ꢄ
4V
× ꢀ
ꢃ × 0.85
RSENSE
=
+
ꢂ
ꢅ
(1a)
Calculate the minimum output capacitance
required using:
R
= 138mW @ 120mW
SENSE
3a.
3b.
Determine the inductance required using
equation 2.
6
V
+ V
ꢀ
IN(MAX) ꢃ
2.510
OUT
C = IOUT (MAX)
(5)
(6)
ꢂ
ꢅ
VOUT
VOUT
ꢁ
ꢄ
LP = (25×10−6 ) × 6 × 0.12
= 18µH
(2a)
4b.
5.
Establish the maximum allowable ESR for the
ouput capacitor:
Determine the minimum inductor current rating
required.
VOUT RSENSE
RESR
<
150mV
(4a)
235mV 6 × (2.5×10−6
120mΩ
)
As a final design check, evaluate the system
stability (no compensation, single pole response)
by using the following equation:
IL PEAK
=
+
= 2.79A
18 ×10–6
R
× (VOUT + V
)
ꢀ
!
"
(7)
SENSE
IN (MIN)
∆VOUT ≤ (6 ×10−6 ) ×
#
LP
$
where R
used.
and L are the actual values to be
P
SENSE
7
ML4863
DESIGN CONSIDERATIONS (Continued)
3c.
3d.
4a.
Specify the inductor’s DC winding resistance:
= 90mW
LAYOUT
L
Good PC board layout practices will ensure the proper
operation of the ML4863. Important layout considerations
follow:
DCR
Specify the coupled inductor's turn ratio:
Np : Ns = 1:1
• The connection from the current sense resistor to the
SENSE pin of the ML4863 should be made by a
separate trace and connected right at the sense resistor
lead.
Calculate the minimum output capacitance
required using equation 5.
5+ 6
2.5×10−6
• The V bypass capacitor needs to be located close to
C = 0.50 × ꢁ ꢄ ×
CC
ꢃ ꢆ
= 55µF
(5a)
(6a)
the ML4863 for adequate filtering of the IC's internal
bias voltage.
ꢂ ꢅ
5
0.1
4b.
Establish the maximum ESR for the output
capacitor using equation 6.
• Trace lengths from the capacitors to the inductor, and
from the inductor to the FET should be as short as
possible to minimize noise and ground bounce.
0.1× 0.12
150mV
RESR
<
= 80mW
• Power and ground planes must be large enough to
handle the current the converter has been designed for.
Based on these calculations, the design should use two
100µF capacitors, with an ESR of 100mW each, in parallel
to meet the capacitance and ESR requirements.
See Figure 5 for a sample PC board layout.
5.
As a final design check, evaluate the system
stability using equation 7.
0.12× (5+ 4)
18 ×10–6
) × ꢆ
"
= 360mV (7a)
100mV ≤ (6 ×10−6
#
$
!
Since the inequality is met, the circuit should be stable.
Some typical application circuits are shown in Figures 2, 3,
and 4.
V
V
OUT
OUT
5V, 1A
Coiltronics
CTX20-4
5V, 2A
Dale
LPE6562
400µF
800µF
V
V
IN
IN
47µF
100µF
ML4863
GND
ML4863
GND
NDS9955
V
V
IN
IN
SENSE OUT 2
SHDN OUT 1
SENSE OUT 2
SHDN OUT 1
NDS9410
V
V
CC
V
V
CC
FB
FB
NDS9410
1µF
1µF
100mΩ
50mΩ
Figure 2. 5V, 1A Circuit
Figure 3. 5V, 2A Circuit
8
ML4863
12V
C4
C5
33µF
20V
33µF
20V
5V
C6
C7
C8
C9
100µF
6.3V
100µF
6.3V
100µF
6.3V
100µF
6.3V
T1
DALE
LPE-6562-A145
3.3V
C13
100µF
6.3V
7
4
9
8
3
C10
100µF
6.3V
C11
100µF
6.3V
C12
100µF
6.3V
1,5
6,10
2
NDS9955
Q1A
Q1B
Q2A
Q2B
MMDF3N03
ML4863
GND
R1
120mΩ
V
V
IN
IN
C1
C2
33µF
20V
33µF
20V
SENSE OUT 2
SHDN OUT 1
R2
30mΩ
SHDN
V
V
CC
FB
C3
1µF
50V
R3
60mΩ
Figure 4. 5W Multiple Output DC-DC Converter
Figure 5. Typical PC Board Layout
9
ML4863
PHYSICAL DIMENSIONS inches (millimeters)
Package: S08
8-Pin SOIC
0.189 - 0.199
(4.80 - 5.06)
8
0.148 - 0.158 0.228 - 0.244
(3.76 - 4.01) (5.79 - 6.20)
PIN 1 ID
1
0.017 - 0.027
(0.43 - 0.69)
(4 PLACES)
0.050 BSC
(1.27 BSC)
0.059 - 0.069
(1.49 - 1.75)
0º - 8º
0.012 - 0.020
(0.30 - 0.51)
0.015 - 0.035
(0.38 - 0.89)
0.006 - 0.010
(0.15 - 0.26)
0.055 - 0.061
(1.40 - 1.55)
0.004 - 0.010
(0.10 - 0.26)
SEATING PLANE
ORDERING INFORMATION
PART NUMBER
TEMPERATURE RANGE
PACKAGE
ML4863CS
ML4863ES
ML4863IS (Obsolete)
0ºC to 70ºC
–20ºC to 70ºC
–40ºC to 85ºC
8-Pin SOIC (S08)
8-Pin SOIC (S08)
8-Pin SOIC (S08)
© Micro Linear 1997. is a registered trademark of Micro Linear Corporation. All other trademarks are the property of their respective owners.
Products described herein may be covered by one or more of the following U.S. patents: 4,897,611; 4,964,026; 5,027,116; 5,281,862; 5,283,483; 5,418,502;
5,508,570; 5,510,727; 5,523,940; 5,546,017; 5,559,470; 5,565,761; 5,592,128; 5,594,376; 5,652,479; 5,661,427; 5,663,874; 5,672,959; 5,689,167. Japan: 2,598,946;
2,619,299; 2,704,176. Other patents are pending.
2092 Concourse Drive
San Jose, CA 95131
Tel: 408/433-5200
Fax: 408/432-0295
www.microlinear.com
Micro Linear reserves the right to make changes to any product herein to improve reliability, function or design. Micro Linear does not assume any liability
arising out of the application or use of any product described herein, neither does it convey any license under its patent right nor the rights of others. The circuits
contained in this data sheet are offered as possible applications only. Micro Linear makes no warranties or representations as to whether the illustrated circuits
infringe any intellectual property rights of others, and will accept no responsibility or liability for use of any application herein. The customer is urged to consult
with appropriate legal counsel before deciding on a particular application.
DS4863-01
10
ML4863ES 相关器件
| 型号 | 制造商 | 描述 | 价格 | 文档 |
| ML4863IS | MICRO-LINEAR | High Efficiency Flyback Controller | 获取价格 |
|
| ML4865 | FAIRCHILD | High Voltage High Current Boost Regulator | 获取价格 |
|
| ML4865 | MICRO-LINEAR | High Voltage High Current Boost Regulator | 获取价格 |
|
| ML4865CS-2 | FAIRCHILD | High Voltage High Current Boost Regulator | 获取价格 |
|
| ML4865CS-2 | MICRO-LINEAR | High Voltage High Current Boost Regulator | 获取价格 |
|
| ML4865CS-2 | ROCHESTER | Switching Regulator, Current-mode, 2A, 200kHz Switching Freq-Max, PDSO8, SOIC-8 | 获取价格 |
|
| ML4865CS2 | ROCHESTER | 2 A SWITCHING REGULATOR, 200 kHz SWITCHING FREQ-MAX, PDSO8, SOIC-8 | 获取价格 |
|
| ML4865CS2 | FAIRCHILD | Switching Regulator, Current-mode, 2A, 200kHz Switching Freq-Max, CMOS, PDSO8, SOIC-8 | 获取价格 |
|
| ML4865CS2X | FAIRCHILD | Switching Regulator, Current-mode, 2A, 200kHz Switching Freq-Max, PDSO8, SOIC-8 | 获取价格 |
|
| ML4865CSX-2 | FAIRCHILD | Switching Regulator, Current-mode, 2A, 200kHz Switching Freq-Max, PDSO8, SOIC-8 | 获取价格 |
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