MC34025 Datasheet, PDF (1/20 Pages) ON Semiconductor – High Speed Double-Ended PWM Controller

High Speed Double-Ended
PWM Controller
Order this document by MC34025/D
MC34025
MC33025
The MC34025 series are high speed, fixed frequency, double–ended
pulse width modulator controllers optimized for high frequency operation.
They are specifically designed for Off–Line and DC–to–DC converter
applications offering the designer a cost effective solution with minimal
external components. These integrated circuits feature an oscillator, a
temperature compensated reference, a wide bandwidth error amplifier, a
high speed current sensing comparator, steering flip–flop, and dual high
current totem pole outputs ideally suited for driving power MOSFETs.
Also included are protective features consisting of input and reference
undervoltage lockouts each with hysteresis, cycle–by–cycle current limiting,
and a latch for single pulse metering.
The flexibility of this series allows it to be easily configured for either
current mode or voltage mode control.
• 50 ns Propagation Delay to Outputs
• Dual High Current Totem Pole Outputs
• Wide Bandwidth Error Amplifier
• Fully–Latched Logic with Double Pulse Suppression
• Latching PWM for Cycle–By–Cycle Current Limiting
• Soft–Start Control with Latched Overcurrent Reset
• Input Undervoltage Lockout with Hysteresis
• Low Start–Up Current (500 µA Typ)
• Internally Trimmed Reference with Undervoltage Lockout
• 90% Maximum Duty Cycle (Externally Adjustable)
• Precision Trimmed Oscillator
• Voltage or Current Mode Operation to 1.0 MHz
• Functionally Similar to the UC3825
16
Vref
4
Clock
5
RT
CT
6
7
Ramp
Error Amp ³
Output
Noninverting 2
Input
Inverting
Input 1
8
Soft–Start
Simplified Application
Oscillator
5.1V
Reference
UVLO
Latching
PWM and
Error
Amp
Steering
Flip Flop
Soft–Star
t
10 Ground
This device contains 227 active transistors.
15
VCC
13
VC
14
Output B
11
Output A
Power
12 ^Ground
9
Current
Limit/
Shutdown
16
1
P SUFFIX
PLASTIC PACKAGE
CASE 648
16
1
DW SUFFIX
PLASTIC PACKAGE
CASE 751G
(SO–16L)
PIN CONNECTIONS
Error Amp
Inverting Input ¹
Error Amp ₂
Noninverting Input
Error Amp Output ³
16 _Vref
15 _VCC
14 _{Output B}
Clock ⁴
RT ⁵
13 _VC
12 _{Power Ground}
CT 6
Ramp ⁷
Soft–Start ⁸
11 Output A
10 _Ground
9 ^{Current Limit/}
Shutdown
(Top View)
ORDERING INFORMATION
Device
Operating
Temperature Range
Package
MC33025DW
SO–16L
TA = – 40° to +105°C
MC33025P
Plastic DIP
MC34025DW
MC34025P
TA = 0° to +70°C
SO–16L
Plastic DIP
MOTOROLA ANALOG IC DEVICE DATA
© Motorola, Inc. 1996
Rev 1
1