ML4825 Micro Linear, ML4825 Datasheet

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ML4825

Manufacturer Part Number
ML4825
Description
High Frequency Power Supply Controller
Manufacturer
Micro Linear
Datasheet

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GENERAL DESCRIPTION
The ML4825 High Frequency PWM Controller is an IC
controller optimized for use in Switch Mode Power
Supply designs running at frequencies to 1MHz.
Propagation delays are minimal through the comparators
and logic for reliable high frequency operation while slew
rate and bandwidth are maximized on the error amplifier.
This controller is designed to work in either voltage or
current mode and provides for input voltage feed forward.
A 1V threshold current limit comparator provides cycle-
by-cycle current limit while exceeding a 1.4V threshold
initiates a soft-start cycle. The soft start pin doubles as a
maximum duty cycle clamp. An under-voltage lockout
circuit with 800mV of hysteresis assures low startup
current and drives the outputs low.
This controller is similar in architecture and performance
to the UC1825 controller, however the ML4825 includes
many features not found on the 1825. These features are
set in Italics .
BLOCK DIAGRAM
7
5
6
3
2
1
8
9
R
E/A OUT
NI
INV
SS
I
C
RAMP
LIM
T
T
/SD
1.4V
1V
+
+
+
(Pin configuration shown for 16-pin version)
ERROR
1.25V
+
AMP
OSC
High Frequency Power Supply Controller
9 A
+
V+
COMP
R
S
+
P
C
TF.F.
Q
1V
Q
Q
FEATURES
Practical operation at switching frequencies to 1.0MHz
High current (2A peak) dual totem pole outputs
Wide bandwidth error amplifier
Fully latched logic with double pulse suppression
Pulse-by-pulse current limiting
Soft start and maximum duty cycle control
Under voltage lockout with hysteresis
Precision trimmed 5.1V bandgap reference
Pin compatible improved replacement for UC1825
Fast shut down path from current limit to outputs
Outputs preset to known condition after under voltage
lockout
Soft start latch ensures full soft start cycle
Outputs pull low for undervotage lockout
LOCKOUT
VOLTAGE
UNDER
*Some Packages Are Obsolete or End Of Life
R
S
+
9V
Q
V
ENABLE
POWER GND
POWER V
REF
V
REF
INTERNAL
GEN
BIAS
C
+
SIGNAL GND
CLOCK OUT
4V
ML4825*
PWR GND
1.5V V
PWR V
OUT A
OUT B
V
REF
CC
C
May 1997
13
11
14
12
16
15
10
4
1

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ML4825 Summary of contents

Page 1

... High Frequency Power Supply Controller GENERAL DESCRIPTION The ML4825 High Frequency PWM Controller controller optimized for use in Switch Mode Power Supply designs running at frequencies to 1MHz. Propagation delays are minimal through the comparators and logic for reliable high frequency operation while slew rate and bandwidth are maximized on the error amplifier ...

Page 2

... OUT A GND I /SD LIM PIN NAME 9 (12) I LIM 10 (13) GND 11 (14) OUT A 12 (15) PWR GND Return for the high current totem 13 (17 (18) OUT B for T 15 (19 (20) 5.1V REF ML4825 20-Pin PLCC OUT B CLOCK ...

Page 3

... ML4825IX, ML4825CX ....................................... 150 C Storage Temperature Range ..................... – 150 C Lead Temperature (soldering 10 sec.) ..................... 260 C Thermal Resistance ( Plastic DIP or SOIC ......................................... 65 C/W Plastic Chip Carrier (PCC) ................................ 60 C/W OPERATING CONDITIONS Temperature Range ML4825CX ................................................ ML4825IX .............................................. – 1000pF Operating Temperature Range CONDITIONS 10V < ...

Page 4

... ML4825 ELECTRICAL CHARACTERISTICS PARAMETER ERROR AMPLIFIER (Continued) CMRR PSRR Output Sink Current Output Source Current Output High Voltage Output Low Voltage Unity Gain Bandwidth Slew Rate PWM COMPARATOR Ramp Bias Current Duty Cycle Range E/A OUT Zero DC Threshold Delay to Output SOFT START ...

Page 5

... FUNCTIONAL DESCRIPTION OSCILLATOR The ML4825 oscillator charges the external capacitor (C with a current (I ) equal to 3/R . When the capacitor SET SET voltage reaches the upper threshold (Ramp Peak), the comparator changes state and the capacitor discharges to the lower threshold (Ramp Valley) through Q1. While the capacitor is discharging, Q2 provides a high pulse ...

Page 6

... Inhibit line) for ease in implementing the soft start function. OUTPUT DRIVER STAGE The ML4825 Output Driver peak output high speed totem pole circuit designed to quickly switch the gates of capacitive loads, such as power MOSFET transistors. ...

Page 7

... Figure 9. Rise/Fall Time (C = 1000pF –60 –40 – 100 TEMPERATURE (°C) Figure 11. Supply Current vs. Temperature 0 –0 200 0 Figure 10. Rise/Fall Time (C 120 140 ML4825 –2 100 200 300 400 500 TIME (ns) = 10,000pF ...

Page 8

... BSC (1.40 - 1.65) (2.54 BSC) 0.015 MIN (0.38 MIN) SEATING PLANE 0.016 - 0.022 (0.40 - 0.56) Package: S16W 16-Pin Wide SOIC 0.291 - 0.301 0.398 - 0.412 (7.39 - 7.65) (10.11 - 10.47) 0.050 BSC (1.27 BSC) 0.095 - 0.107 (2.41 - 2.72) 0º - 8º 0.005 - 0.013 SEATING PLANE (0.13 - 0.33) ML4825 0.295 - 0.325 (7.49 - 8.26) 0.008 - 0.012 0º - 15º (0.20 - 0.31) 0.022 - 0.042 0.009 - 0.013 (0.56 - 1.07) (0.22 - 0.33) 11 ...

Page 9

... PART NUMBER ML4825CP ML4825CS ML4825CQ ML4825IP ML4825IS ML4825IQ © Micro Linear 1997 is a registered trademark of Micro Linear Corporation Products described in this document may be covered by one or more of the following patents, U.S.: 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; Japan: 2598946; 2619299. Other patents are pending. ...

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