ON MC33466 Fixed frequency pwm micropower dc-to-dc converter Datasheet

Order this document by MC33466/D
The MC33466 series are micropower switching voltage regulators,
specifically designed for handheld and laptop applications, to provide
regulated output voltages using a minimum of external parts. A wide choice
of output voltages are available. These devices feature a very low quiescent
bias current of 15 µA typical.
The MC33466H–XXJT1 series features a highly accurate voltage
reference, an oscillator, a pulse width modulation (PWM) controller, a driver
transistor (Lx), an error amplifier and feedback resistive divider.
FIXED FREQUENCY PWM
MICROPOWER DC–to–DC
CONVERTER
SEMICONDUCTOR
TECHNICAL DATA
The MC33466H–XXLT1 is identical to the MC33466H–XXJT1, except
that a drive pin (EXT) for an external transistor is provided.
Due to the low bias current specifications, these devices are ideally suited
for battery powered computer, consumer, and industrial equipment where an
extension of useful battery life is desirable.
TAB
1
MC33466 Series Features:
•
Low Quiescent Bias Current of 15 µA
•
High Output Voltage Accuracy of ±2.5%
•
Low Startup Voltage of 0.9 V at 1.0 mA
•
Soft–Start = 500 µs
•
Surface Mount Package
H SUFFIX
PLASTIC PACKAGE
CASE 1213
(SOT–89)
PIN CONNECTIONS
MC33466H–XXJT1
Ground
1
Output
2
Lx
3
ORDERING INFORMATION
Device
Output
Voltage
MC33466H–30JT1
MC33466H–33JT1
MC33466H–50JT1
3.0
3.3
5.0
Int.
Switch
S
it h
MC33466H–30LT1
MC33466H–33LT1
MC33466H–50LT1
3.0
3.3
5.0
Ext.
S it h
Switch
Di
Drive
Type
Operating
Temperature Range
(Top View)
SOT–89
(T
(Tape)
)
MC33466H–XXLT1
Ground
1
Output
2
EXT
3
Other voltages from 2.5 V to 7.5 V, in 0.1 V increments are available. Consult factory for
information.
Tab
(Tab is connected
to Pin 2)
(Top View)
 Motorola, Inc. 1999
MOTOROLA ANALOG IC DEVICE DATA
(Tab is connected
to Pin 2)
Package
(Tape/Reel)
SOT–89
(T
(Tape)
)
30° to +80°C
80°C
TA = –30°
Tab
Rev 4, 08/1999
1
MC33466
Representative Block Diagrams
MC33466H–XXJT1
D
VO
L
3
Vin
2
VLx Limiter
Lx
Cin
Output
(Voltage
Feedback)
Drive
CO
PWM
Controller
Phase
Comp
50 kHz
Oscillator
Vref
Soft–Start
1
Gnd
MC33466H–XXLT1
L
Vin
D
VO
Cin
2
Rb
Q
3
Output
(Voltage
Feedback)
Drive
EXT
Cb
CO
PWM
Controller
100 kHz
Oscillator
Phase
Comp
Soft–Start
Vref
1
Gnd
XX Denotes Output Voltage
This device contains 100 active transistors.
MAXIMUM RATINGS (TC = 25°C, unless otherwise noted.)
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Rating
Symbol
Value
Unit
Power Supply Voltage (Transient)
VO
12
V
Power Supply Voltage (Operating)
VO
8.0
V
External Pin Voltage
VEXT
–0.3 to VO
V
Lx Pin Voltage
VLx
12
V
EXT Pin Source/Sink Current
IEXT
50/50
mA
ILx
250
mA
500
200
mW
°C/W
Operating Junction Temperature
PD
RθJA
TJ
125
°C
Operating Ambient Temperature
TA
–30 to +80
°C
Tstg
–40 to +125
°C
Lx Pin Sink Current
Power Dissipation and Thermal Characteristics
H Suffix, Plastic Package Case 1213 (SOT–89)
Maximum Power Dissipation @ TA = 25°C
Thermal Resistance, Junction–to–Air
Storage Temperature Range
NOTE:
2
ESD data available upon request.
MOTOROLA ANALOG IC DEVICE DATA
MC33466
ELECTRICAL CHARACTERISTICS (VCC = 2.0 V, IO = 10 mA and TA = 25°C, unless otherwise noted.)
Characteristic
Symbol
Min
Typ
Max
40
80
50
100
60
120
Unit
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OSCILLATOR
Frequency
LX output
EXT output
fosc
kHz
Oscillator Minimum Startup Voltage (IO = 0 mA)
Vstart
–
0.8
0.9
V
Oscillator Minimum Supply Voltage (IO = 0 mA)
VCC
0.7
–
–
V
60
63
80
–
–
–
–
–
–
VLxLim
0.65
0.8
1.0
V
ILKG
–
–
0.5
µA
1.5
1.575
2.0
–
–
–
–
–
–
1.5
1.575
2.0
–
–
–
–
–
–
70
80
90
2.925
3.218
4.875
3.0
3.3
5.0
3.075
3.383
5.125
0.5
2.0
–
–
–
–
15
17
30
25
27
45
–
–
–
1.2
1.2
2.0
5.0
5.0
5.0
–
–
–
30
34.5
60
50
56
90
–
–
–
1.2
1.2
2.0
5.0
5.0
5.0
LX OUTPUT (JT1 SUFFIX)
ON State Sink Current (VLx = 0.4 V)
30KT1 Suffix
33KT1 Suffix
50KT1 Suffix
VLx Voltage Limit (Note 1)
OFF State Leakage Current (VLx = 6.0 V)
ILx
mA
EXT OUTPUT (LT1 SUFFIX)
ON State Source Current (VEXT = VO – 0.4 V)
30LT1 Suffix
33LT1 Suffix
50LT1 Suffix
OFF State Sink Current (VEXT = 0.4 V)
30LT1 Suffix
33LT1 Suffix
50LT1 Suffix
Isource
mA
Isink
mA
TOTAL DEVICE
Maximum Duty Ratio Each Cycle
D
Output Voltage
30KT1 or 30LT1 Suffix
33KT1 or 33LT1 Suffix
50KT1 or 50LT1 Suffix
VO
Soft–Start Time (Note 2)
Tss
Quiescent Bias Current (Vin = 2.0 V, IO = 0 mA)
30JT1 Suffix
33JT1 Suffix
50JT1 Suffix
Quiescent Bias Current (Vin = VO + 0.5 V, IO = 0 mA)
30JT1 Suffix
33JT1 Suffix
50JT1 Suffix
IQ
Quiescent Bias Current (Vin = 2.0 V, IO = 0 mA)
30LT1 Suffix
33LT1 Suffix
50LT1 Suffix
Quiescent Bias Current (Vin = VO + 0.5 V, IO = 0 mA)
30LT1 Suffix
33LT1 Suffix
50LT1 Suffix
IQ
%
V
ms
µA
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ÁÁÁ
µA
NOTES: 1. When the Lx switch is turned on, ILx current carried through the RDS(on) of the Lx switch results in VLx. When VLx reaches VLxLim, the Lx switch is
turned off by the Lx switch protection circuit.
2. The soft–start circuit turn–on sequence is as follows:
a) Vin is applied.
b) The internal IC Vref is held at zero for 200 µs. During this time, the error amplifier output voltage ramps up to the positive voltage rail.
c) The internal reference steps up to 0.7 V after 200 µs delay has timed out.
d) The error amplifier output voltage integrates down to its steady state value. As the error amplifier output integrates down, the output Lx pin of EXT
pin pulse width gradually widens to its steady operating value.
MOTOROLA ANALOG IC DEVICE DATA
3
MC33466
Figure 1. Quiescent Current versus Temperature
Figure 2. Quiescent Current versus Temperature
40
2.0
MC33466H–33JT1
IO = 0 mA
Vin = 2.0 V
I Q , QUIESCENT BIAS CURRENT (µ A)
I Q , QUIESCENT BIAS CURRENT (µ A)
50
30
20
10
–40
0
–20
20
40
60
1.2
0.8
20
40
TA, AMBIENT TEMPERATURE (°C)
Figure 3. Oscillator Frequency versus Temperature
Figure 4. Maximum Duty Ratio
versus Temperature
80
40
–20
0
20
40
60
60
80
80
70
60
–40
80
–20
0
20
40
TA, AMBIENT TEMPERATURE (°C)
Figure 5. Lx Switching Current versus Temperature
Figure 6. VLx Voltage Limit versus Temperature
1.0
VLxLim, V Lx VOLTAGE LIMIT (V)
200
160
120
80
0
–40
80
MC33466H–50JT1
L = 120 µH
IO = 10 mA
Vin = 3.0 V
90
TA, AMBIENT TEMPERATURE (°C)
40
60
100
MC33466H–50JT1
L = 120 µH
IO = 10 mA
Vin = 3.0 V
60
20
–40
I Lx , Lx SWITCHING CURRENT (mA)
0
–20
TA, AMBIENT TEMPERATURE (°C)
Dmax , MAXIMUM DUTY RATIO (%)
fosc , OSCILLATOR FREQUENCY (kHz)
1.6
0.4
–40
80
100
MC33466H–50JT1
IO = 10 mA
Vin = 2.0 V
–20
0
20
40
TA, AMBIENT TEMPERATURE (°C)
4
MC33466H–33JT1
IO = 0 mA
Vin = 5.5 V
60
80
0.9
0.8
0.7
0.6 MC33466H–50JT1
IO = 10 mA
Vin = 2.0 V
0.5
–40
–20
0
20
40
60
80
TA, AMBIENT TEMPERATURE (°C)
MOTOROLA ANALOG IC DEVICE DATA
MC33466
Figure 7. Output Voltage versus Output Current
Figure 8. Output Voltage versus Output Current
6.0
6.0
5.0
4.0
Vin = 4.0 V
Vin = 3.0 V
Vin = 2.0 V
VO , OUTPUT VOLTAGE (V)
VO , OUTPUT VOLTAGE (V)
Vin = 2.0 V
3.0
Vin = 1.0 V
2.0
1.0
MC33466H–50JT1
L = 120 µH
TA = 25°C
0
20
40
60
80
100
120
Vin = 4.0 V
4.0
Vin = 1.5 V
3.0
2.0 MC33466H–50LT1
L = 28 µH
TA = 25°C
1.0
0
100
200
Figure 9. Efficiency versus Output Current
Vin = 2.0 V
600
80
Vin = 1.5 V
60
EFFICIENCY (%)
EFFICIENCY (%)
500
100
80
Vin = 1.0 V
40
MC33466H–30JT1
L = 120 µH
TA = 25°C
Figure 17
20
0
5.0
10
Vin = 1.5 V
60
15
20
25
Vin = 0.9 V
0
30
Vin = 2.0 V
40
MC33466H–30LT1
L = 28 µH
TA = 25°C
Figure 18
20
0
100
200
300
400
500
IO, OUTPUT CURRENT (mA)
IO, OUTPUT CURRENT (mA)
Figure 11. Startup/Hold Voltage versus
Output Current
Figure 12. Startup/Hold Voltage versus
Output Current
600
1.6
VLxLim, V Lx VOLTAGE LIMIT (V)
2.0
Vstart /V hold , VOLTAGE LIMIT (V)
400
Figure 10. Efficiency versus Output Current
100
1.6
1.2
Vstart
0.8
0.4
0
300
IO, OUTPUT CURRENT (mA)
IO, OUTPUT CURRENT (mA)
0
Vin = 3.0 V
5.0
MC33466H–50JT1
L = 120 µH
TA = 25°C
Figure 17
Vhold
0
2.0
4.0
6.0
8.0
IO, OUTPUT CURRENT (mA)
MOTOROLA ANALOG IC DEVICE DATA
10
12
1.4
1.2
Vstart
1.0
MC33466H–50LT1
L = 28 µH
TA = 25°C
Figure 18
0.8
Vhold
0.6
0
20
40
60
80
100
120
IO, OUTPUT CURRENT (mA)
5
MC33466
Figure 14. Startup/Hold Voltage
versus Temperature
MC33466H–50JT1
L = 120 µH
IO = 10 mA
Vin = 3.0 V
Figure 17
5.2
5.1
5.0
4.9
4.8
–40
–20
0
20
40
60
80
1.0
0.8
Vstart
0.6
Vhold
MC33466H–50JT1
L = 120 µH
IO = 3.0 mA
Figure 17
0.4
0.2
–40
–20
0
20
40
60
Figure 15. Supply Current versus Input Voltage
Figure 16. Load Transient Response
250
250
MC33466H–50JT1
L = 120 µH
IO = 10 mA
Figure 17
200
MC33466H–50JT1
L = 120 µH
IO = 1.0 to 30 mA
Vin = 3.0 V
Figure 17
5.4
VO , OUTPUT VOLTAGE (V)
I CC , SUPPLY CURRENT (µ A)
80
TA, AMBIENT TEMPERATURE (°C)
TA, AMBIENT TEMPERATURE (°C)
150
100
50
5.2
I O , OUTPUT CURRENT (µ A)
VO , OUTPUT VOLTAGE (V)
Vstart/V hold, STARTUP/HOLD VOLTAGE (V)
Figure 13. Output Voltage versus Temperature
200
150
5.0
100
4.8
50
4.6
0
0
1.0
2.0
3.0
4.0
Vin, INPUT VOLTAGE (V)
6
5.0
6.0
0
10
20
30
40
50
0
60
t, TIME (ms)
MOTOROLA ANALOG IC DEVICE DATA
MC33466
DEFINITIONS
Quiescent Bias Current – Current which is used to operate
the switching regulator chip and is not delivered to the load.
Leakage Current – Current drawn through a transistor
junction, under a specified collector voltage, when the
transistor is off.
FUNCTIONAL DESCRIPTION
Introduction
The MC33466 series are monolithic power switching
regulators optimized for dc–to–dc converter applications
where power drain must be minimized. The combination of
features in this series allows the system designer to directly
implement step–up, step–down or flyback converters with a
small number of external components. Potential applications
include low power consumer products and battery powered
portable products. Typical application circuits are shown in
Figures 17 through 21.
Operating Description
The MC33466 series converters operate as a fixed
frequency voltage mode regulator. Operation is intended to
be in the discontinuous mode, where the inductor current
ramps up to a peak value which is greater than or equal to
twice the value of the dc input current during the on–time of
the transistor switch. During the off–time of the transistor
switch, the inductor current ramps down to zero and remains
at zero until another switching cycle begins.
Because the output voltage pin is also used as the supply
voltage for powering internal circuitry, an external startup
circuit is needed in step–down converter and flyback designs
to provide initial power to the integrated circuit to begin
switching. The startup circuit needed can be three discrete
components, as shown in Figure 19, or a micropower
undervoltage sensor, as shown in Figure 20.
Oscillator
The oscillator frequency, is internally programmed to
50 kHz. The timing capacitor (CT) discharge to charge ratio
of the oscillator is designed for a maximum duty cycle of 80%
at the Lx or EXT output. During the charge of CT, the
oscillator generates an internal blanking pulse that holds the
PWM control off, disabling the output transistor drive. The
oscillator peak and valley thresholds are 0.5 V and ground,
respectively.
Pulse Width Modulator
The Pulse Width Modulator consists of a comparator with
the oscillator ramp voltage applied to the inverting input,
while the error amplifier output is applied to the noninverting
input. Output switch conduction is initiated when the timing
capacitor is charged to its peak voltage value. When the
timing capacitor ramp discharges to a voltage below the error
amplifier output, the comparator resets a latch terminating
output transistor drive for the duration of the oscillator ramp
period.
Error Amplifier and Reference
An Error Amplifier is provided which has a nominal 80 dB
of voltage gain at dc. Internal compensation components
provide poles at 0.25 Hz, 30 kHz and 33 kHz. Two zeros are
provided at 1.0 kHz and at 2.5 kHz. The output voltage value
is set by the internal voltage divider and a 0.7 V reference
which is trimmed to an accuracy of ±2.5%. Because the loop
compensation components are located within the IC,
discontinuous mode operation is recommended for most
applications.
Driver and Output Switch
To aid in system design flexibility and conversion
efficiency, two output driver options are provided. The
MC33466H–XXJT1 converters have an internal drive
transistor which is capable of sinking currents greater than
60 mA into the Lx pin. An internal VLx limiter circuit senses if
the Lx pin voltage exceeds 1.0 V during ton and turns off the
drive transistor. The MC33466H–XXJT1 provides output
drive for an external transistor.
Applications
The following converter applications show the simplicity
and flexibility of the converter architecture. Three main
converter topologies are demonstrated in Figures 17 through
21.
Figure 17. MC33466H–50KT1 Typical
Step–Up Application
Figure 18. MC33466H–50LT1 Typical
Step–Up Application
MBRD520LT1
MBRD520LT1
28 µH
120 µH
Vin
Vin
MC33466H–50KT1
2
3
Lx
VO
VO
22 µF
22 µF
22 µF
300
MMBT2222ALT1
Gnd
1
MOTOROLA ANALOG IC DEVICE DATA
0.01 µF
MC33466H–50LT1
2
VO
VO
5.0 V
3
100 µF
EXT
Gnd
1
7
MC33466
Figure 19. MC33466H–33JT1 Step–Down Application
Startup Circuit
MMBT2222ALT1
1.5 k
BZX84C3V3LT1
3.3 V
47 µH
MMBT2907ALT1
Vin
MBRD0520LT1
1.0 k
330 µF
VO
3.3 V
320 mA
MC33466H–33JT1
100
3
Lx
2
VLx Limiter
Output
Drive
PWM
Controller
330 µF
330 µF
Phase
Comp
50 kHz
Oscillator
Soft–Start
Vref
1
Test
8
Gnd
Condition
Results
Line Regulation
Vin = 5.0 V to 10 V, IO = 320 mA
7 mV = ±0.1%
Load Regulation
Vin = 7.0 V, IO = 3.3 mA to 320 mA
3 mV = ±0.04%
Output Ripple
Vin = 7.0 V, IO = 320 mA
70 mVpp
Efficiency
Vin = 7.0 V, IO = 320 mA
63.8%
MOTOROLA ANALOG IC DEVICE DATA
MC33466
Figure 20. Micropower Step–Down Application
Startup Circuit
MC33464N–30ATR
MMBT2222ALT1
2
In
Out
Gnd
3
1
10 k
10 k
47 µH
MMBT2907ALT1
Vin
5.0 V
100 µF
VO
3.3 V
300 mA
MBRD0520LT1
1.0 k
MC33466H–33JT1
100
3
Lx
2
VLx Limiter
Output
100 µF
Drive
PWM
Controller
Phase
Comp
50 kHz
Oscillator
Soft–Start
Vref
1
NOTE:
Gnd
Using the MC33464N–30ATR reduces current drawn in the startup circuit to 1 mA during normal operation.
MOTOROLA ANALOG IC DEVICE DATA
9
MC33466
Figure 21. Flyback Application
Startup Circuit
1.5 k
MMBT2222ALT1
3.3 V
MMBT2907ALT1
Vin
100 µF
VO
3.3 V
1.0 k
MC33466H–33KT1
100
3
Lx
2
VLx Limiter
Output
100 µF
Drive
PWM
Controller
Phase
Comp
50 kHz
Oscillator
Soft–Start
Vref
1
10
Gnd
MOTOROLA ANALOG IC DEVICE DATA
MC33466
Figure 22. Design Equations
Calculation
Step–Down
Step–Up
Flyback
L
t (Vin –2IVO)(ton)
t (Vin2I)(ton)
t (Vin2I)(ton)
O
ton
in
D
fs
D
t
IL(avg)
D
fs
t
(V )
O
(V )
in
IO
IL(pk)
(V
in
in
(V
D
fs
*
t
V )
in
O
(V )
O
ƪǒ Ǔ ƫ
V
Ns (V )
in
Np
Iin
* VO)(ton)
(V
L
Vripple(pp)
I
L(pk)
in
ȱȧǒ
Ȳ
1
8fsC
Ǔ
O
2
) VO
Iin
* Vsat)(ton)
L
O
(V
ȳȧ
ȴ
) (ESR)2
in
* Vsat)(ton)
L
1
2
The following converter design characteristics must be chosen:
Vin – Nominal Operating dc input voltage
VO – Desired dc output voltage
IO – Desired dc output current
Vripple(pp) – Desired peak–to–peak output ripple voltage. For best performance the ripple voltage should be kept to a low value since it will directly
affect line and load regulation. Capacitor CO should be a low equivalent series resistance (ESR) electrolytic designed for switching regulator
applications.
D – Operating duty cycle = ton(fs). This parameter must be chosen to be <0.5 for step–up and flyback applications.
NOTES: 1. Vsat – Saturation voltage of the switching transistor.
2. Iin – DC input switch.
3. fs – Switching frequency, nominally 50 kHz.
4. RO – Load resistance. RO = VO/IO.
5. Ns, Np – In flyback applications Ns is the number of turns of the secondary transformer winding; Np is the number of the primary winding turns.
Design Example – Step–down Application
Required: Vin = 8.0 V, an output voltage of 3.3 V at 300 mA is desired with an output ripple of less than 300 mVpp.
+ I O + 11 W
V
R
O
O
t VO + 3.38 + 0.41. Choose D = 0.33.
V
1. Because this is a discontinuous mode design, D
in
2. t on
3. L
+ 6.6 µs.
[ fsD + (500.33
kHz)
3.3)(6.6 µs)
+ 51.7 µH.
t (Vin –2IVO)(ton) + (8 – [2(0.3)]
O
Choose L = 47 µH. Coilcraft part number DO3316P–473.
4. I
L(pk)
5. ESR
3.3)(6.6 µs)
+ (Vin – VLO)(ton) + (8 – (47
+ 660 mA.
µH)
t
V
ripple(pp)
I
L(pk)
mV)
+ (300
+ 0.455 W.
(660 mA)
Choose CO = two parallel AVX 330 µF tantalum chip capacitors. Part Number TAJE337M006.
Specified maximum ESR for each is 0.9 Ω.
The complete design schematic is shown in Figure 19.
MOTOROLA ANALOG IC DEVICE DATA
11
MC33466
OUTLINE DIMENSIONS
H SUFFIX
PLASTIC PACKAGE
CASE 1213–01
(SOT–89)
ISSUE O
A
D
A2
C
B
D1
E1
E
L1
B
0.10
B1
e
M
C B
S
A
S
2X
0.10
M
C B
S
A
S
C
NOTES:
1. DIMENSIONS ARE IN MILLIMETERS.
2. INTERPRET DIMENSIONS AND TOLERANCING
PER ASME Y14.5M, 1994.
3. DATUM C IS A SEATING PLANE.
DIM
A2
B
B1
C
D
D1
E
E1
e
e1
L1
MILLIMETERS
MIN
MAX
1.40
1.60
0.37
0.57
0.32
0.52
0.30
0.50
4.40
4.60
1.50
1.70
–––
4.25
2.40
2.60
1.50 BSC
3.00 BSC
0.80
–––
e1
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12
◊
MC33466/D
MOTOROLA ANALOG IC DEVICE
DATA
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