Micro Linear Corporation ML4863IS, ML4863CS, ML4863ES Datasheet
July 2000
FEATURING
Extended Commercial Temperature Range
-20˚C to 70˚C
for Portable Handheld Equipment
ML4863*
High Efficiency Flyback Controller
GENERAL DESCRIPTION
The ML4863 is a flyback controller designed for use in
multi-cell battery powered systems such as PDAs and
FEATURES
■ Variable frequency current mode control and
synchronous rectification for high efficiency
notebook computers. The flyback topology is ideal for
systems where the battery voltage can be either above or
■ Minimum external components
below the output voltage, and where multiple output
voltages are required.
■ 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
■ High frequency operation (>200kHz) minimizes the
size of the magnetics
control output is supplied to provide the highest possible
conversion efficiency (greater than 85% efficiency over a
1mA to 1A load range).
The ML4863 has been designed to operate with a
■ Flyback topology allows multiple outputs in addition to
the regulated 5V
■ Built-in overvoltage and current limit protection
minimum number of external components to optimize
space and cost. *Some Packages Are Obsolete
BLOCK DIAGRAM
3
1
4
SHDN
V
IN
V
FB
R
gm
4.5V
LDO
I
BIAS & UVLO
18mV
18mV
CURRENT
COMPARATOR
+
COMP
–
RECTIFIER
COMPARATOR
–
COMP
+
V
FB
V
CC
SWITCHING
CONTROL
BLANKING
V
CC
5
–
+
V
REF
V
CC
A1
CROSS-CONDUCTION
PROTECTION
A2
V
CC
V
FB
GND
8
OUT 1
6
OUT 2
7
SENSE
2
1
ML4863
PIN CONFIGURATION
PIN DESCRIPTION
8-Pin SOIC (S08)
V
IN
SENSE
SHDN
V
FB
TOP VIEW
ML4863
1
2
3
4
8
GND
7
OUT 2
6
OUT 1
5
V
CC
PIN NAME FUNCTION
1V
IN
Battery input voltage
2 SENSE Secondary side current sense
3 SHDN Pulling this pin high initiates a
shutdown mode to minimize battery
drain
4V
FB
Feedback input from transformer
secondary, and supply voltage when
V
> 4.5V
OUT
PIN NAME FUNCTION
5V
CC
Internal power supply node for
connection of a bypass capacitor
6 OUT 1 Flyback primary switch MOSFET driver
output
7 OUT 2 Flyback synchronous rectifier MOSFET
driver output
8 GND Analog signal ground
2
ABSOLUTE MAXIMUM RATINGS
ML4863
Absolute maximum ratings are those values beyond which
the device could be permanently damaged. Absolute
Lead Temperature (Soldering 10 Sec.) ..................... 260ºC
Thermal Resistance (qJA) .................................... 160ºC/W
maximum ratings are stress ratings only and functional
device operation is not implied.
V
................................................................. GND – 0.3V to 18V
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
OPERATING CONDITIONS
Temperature Range
ML4863CS................................................. 0ºC to 70ºC
ML4863ES ............................................. –20ºC to 70ºC
ML4863IS .............................................. –40ºC to 85ºC
VIN Operating Range ...................................3.15V to 15V
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, VIN = 12V, TA = Operating Temperature Range (Note 1)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
OSCILLATOR
t
ON
ON Time C Suffix 2.1 2.5 2.8 µs
E/I Suffix 2.1 2.5 2.95 µs
Minimum Off Time VFB = 0V 450 650 850 ns
VFB REGULATION
Total Variation Line, Load, & Temp 4.85 5 5.15 V
OUTPUT DRIVERS
OUT1 Rise Time C
OUT1 Fall Time C
OUT2 Rise Time C
OUT2 Fall Time Continuous Mode, C
SHDN
Input High Voltage 2.0 V
Input Low Voltage 0.8 V
Input Bias Current SHDN = 5V 5 10 µA
SENSE
SENSE Threshold – Full Load VIN = 5V, VFB = V
SENSE Threshold – Short Circuit VFB = 0V 235 mV
CIRCUIT PROTECTION
= 3nF, 20% to 90% of V
LOAD
= 3nF, 90% to 20% of V
LOAD
= 3nF, 20% to 90% of V
LOAD
90% to 20% of V
Discontinuous Mode, C
90% to 20% of V
LOAD
CC
CC
FB (No Load)
CC
CC
CC
= 3nF,
= 3nF,
LOAD
– 100mV 130 150 160 mV
60 70 ns
60 70 ns
60 70 ns
60 70 ns
125 150 ns
Undervoltage Lockout Start-up Threshold 3.0 3.15 V
Undervoltage Lockout Hysteresis 0.5 0.6 V
3
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