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PDF MC34066 Data sheet ( Hoja de datos )
| Número de pieza | MC34066 | |
| Descripción | (MC33066 / MC34066) HIGH PERFORMANCE RESONANT MODE CONTROLLERS | |
| Fabricantes | Motorola Semiconductors | |
| Logotipo |  |
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Order this document by MC34066/D
High Performance
Resonant Mode Controllers
The MC34066/MC33066 are high performance resonant mode
controllers designed for off–line and dc–to–dc converter applications that
utilize frequency modulated constant on–time or constant off–time control.
These integrated circuits feature a variable frequency oscillator with
programmable deadtime, precision retriggerable one–shot timer,
temperature compensated reference, high gain wide–bandwidth error
amplifier with a precision output clamp, steering flip–flop, and dual high
current totem pole outputs ideally suited for driving power MOSFETs.
Also included are protective features consisting of a high speed fault
comparator and latch, programmable soft–start circuitry, input undervoltage
lockout with selectable thresholds, and reference undervoltage lockout.
These devices are available in dual–in–line and surface mount packages.
• Variable Frequency Oscillator with a Control Range Exceeding 1000:1
• Programmable Oscillator Deadtime Allows Constant Off–Time Operation
• Precision Retriggerable One–Shot Timer
• Internally Trimmed Bandgap Reference
• 5.0 MHz Error Amplifier with Precision Output Clamp
• Dual High Current Totem Pole Outputs
• Selectable Undervoltage Lockout Thresholds with Hysteresis
• Enable Input
• Programmable Soft–Start Circuitry
• Low Startup Current for Off–Line Operation
MC34066
MC33066
HIGH PERFORMANCE
RESONANT MODE
CONTROLLERS
SEMICONDUCTOR
TECHNICAL DATA
P SUFFIX
PLASTIC PACKAGE
CASE 648
DW SUFFIX
PLASTIC PACKAGE
CASE 751G
(SO–16L)
PIN CONNECTIONS
Simplified Block Diagram
VCC
15
Enable/
UVLO Adjust 9
Osc
Deadtime 1
Osc RC
Osc Control 2
Current 3
One–Shot RC
16
VCC UVLO
Reference
Regulator
Variable
Frequency
Oscillator
One–Shot
Vref UVLO
Steering
Flip–Flop
Aout
Bout
Error Amp
Clamp
Error Amp
Out 6 Error
Amplifier
Error Amp +
8
Error Amp –
7
CSoft–Start
11
Soft–Start
Fault–Detector/
Latch
MOTOROLA ANALOG IC DEVICE DATA
5 Vref
Gnd
4
Drive
14 Output A
Drive
12 Output B
Drive Gnd
13
Fault Input
10
Osc Deadtime 1
Osc RC 2
Osc Control 3
Current
Gnd 4
Vref 5
Error Amp Out 6
Error Amp 7
Inverting Input
Error Amp 8
Noninverting Input
(Top View)
16 One–Shot RC
15 VCC
14 Drive Output A
13 Drive Gnd
12 Drive Output B
11 CSoft–Start
10 Fault Input
9
Enable/UVLO
Adjust
ORDERING INFORMATION
Device
Operating
Temperature Range Package
MC34066DW
TA = 0° to +70°C
MC34066P
SO–16L
Plastic DIP
MC33066DW
TA = – 40° to +85°C
MC33066P
SO–16L
Plastic DIP
© Motorola, Inc. 1996
Rev 1
1
1 page  
MC34066 MC33066
Oscillator
The characteristics of the variable frequency Oscillator are
crucial for precise controller performance at high operating
frequencies. In addition to triggering the One–Shot timer and
initiating the output pulse, the Oscillator also determines the
initial voltage for the One–Shot capacitor and defines the
minimum deadtime between output pulses. The Oscillator is
designed to operate at frequencies exceeding 1.0 MHz. The
Error Amplifier can control the oscillator frequency over a
1000:1 frequency range, and both the minimum and
maximum frequencies are easily and accurately
programmed by the proper selection of external components.
The Oscillator also includes an adjustable deadtime feature
for applications requiring additional time between output
pulses.
The functional diagram of the Oscillator and One–Shot
timer is shown in Figure 2. The oscillator capacitor COSC is
initially charged by transistor Q1 through the optional
deadtime resistor RDT. When COSC exceeds the 4.9 V upper
threshold of the oscillator comparator, the base of Q1 is
pulled low allowing COSC to discharge through the external
resistors and the internal Current Mirror. When the voltage on
COSC falls below the comparator’s 3.6 V lower threshold, Q1
turns on and again charges COSC.
2.5ROSC + 5.1
tdchg(min) = (RDT + ROSC)COSCIn RVFO
2.5ROSC + 3.6
RVFO
(1)
The minimum oscillator frequency will result when the IOSC
current is zero, and COSC is discharged through the external
resistors ROSC and RDT. This occurs when the Error Amplifier
output voltage is less than the two diode drops required to
bias the input of the Current Mirror. The maximum oscillator
discharge time is given by Equation 2.
tdchg(max) = (RDT + ROSC) COSCIn
5.1
3.6
(2)
The outputs of the control IC are off whenever the oscillator
capacitor COSC is being charged by transistor Q1. The
minimum time between output pulses (deadtime) can be
programmed by controlling the charge time of COSC. Resistor
RDT reduces the current delivered by Q1 to COSC, thus
increasing the charge time and output deadtime. Varying RDT
from 0 Ω to 1000 Ω will increase the output deadtime from
80 ns to 680 ns with COSC equal to 300 pF. The general
expression for the oscillator charge time is give by
Equation 3.
Figure 2. Oscillator and One–Shot Timer
VCC
tchg(max) = RDT COSC In
5.1–3.6 + 80 ns
5.1–4.9
(3)
Osc Deadtime
ROSC
1
RDT
Osc RC
2
COSC
One–Shot RC
RT 16
CT Osc Control
Current
3
IOSC
RVFO
6
Error Amp
Output
Q1
IOSC
Q2
5.1V
Oscillator
–
+
4.9V/3.6V
One–Shot
–
+
4.9V/3.6V
UVLO + Fault
Current Mirror
If RDT is 0 Ω, COSC charges from 3.6 V to 5.1 V in less than
50 ns. The high slew rate of COSC and the propagation delay
of the comparator make it difficult to control the peak voltage.
This accuracy issue is overcome by clamping the base of Q1
through diode Q2 to a voltage reference. The peak voltage of
the oscillator waveform is thereby precisely set at 5.1 V.
The frequency of the Oscillator is modulated by varying the
current IOSC flowing through RVFO into the Osc Control
Current pin. The control current drives a unity gain Current
Mirror which pulls an identical current from the COSC
capacitor. As IOSC increases, COSC discharges faster thus
decreasing the Oscillator period and increasing the
frequency. The maximum frequency occurs when the Error
Amplifier output is at the upper clamp level, nominally 2.5 V
above the voltage at the Osc Control Current pin. The
minimum discharge time for COSC, which corresponds to the
maximum oscillator frequency, is given by Equation 1.
The minimum and maximum oscillator frequencies are
programmed by the proper selection of resistor ROSC and
RVFO. After selecting RDT for the desired deadtime, the
minimum frequency is programmed by ROSC using
Equations 2 and 3 in Equation 4:
1=
fOSC(min)
tdchg(max)
+
tchg
(4)
The maximum oscillator frequency is set by resistor RVFO
in a similar fashion using Equations 1 and 3 in Equation 5:
1
fOSC(max)
=
tdchg(min)
+
tchg
(5)
The value chosen for resistor RDT will affect the peak
voltage of the oscillator waveform. As RDT is increased from
zero, the time required to charge COSC becomes large with
respect to the propagation delay through the oscillator
comparator. Consequently, the overshoot of the upper
threshold is reduced and the peak voltage on the oscillator
waveform drops from 5.1 V to 4.9 V. The best frequency
accuracy is achieved when RDT is zero ohms.
One–Shot Timer
The One–Shot capacitor CT is charged concurrently with
the oscillator capacitor by transistor Q1, as shown in Figure 2.
The One–Shot period begins when the oscillator comparator
turns off Q1, allowing CT to discharge. The period ends when
resistor RT discharges CT to the threshold of the One–Shot
comparator. Discharging CT from an initial voltage of 5.1 V to
a threshold voltage of 3.6 V results in the One–Shot period
given by Equation 6.
tOS = RT CT In
5.1
3.6
= 0.348 RT CT
(6)
MOTOROLA ANALOG IC DEVICE DATA
5
5 Page 
MC34066 MC33066
NOTES
MOTOROLA ANALOG IC DEVICE DATA
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet MC34066.PDF ] | |
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