ONSEMI MC33468SN

Order this document by MC33468/D
The MC33468 is a micropower step–up switching voltage regulator,
specifically designed for handheld and pager applications, to provide a
regulated output voltage using a minimum of external parts. This device
features a quiescent bias current of 3.0 µA typical.
The MC33468 features a highly accurate voltage reference, an error
amplifier, an oscillator, a variable frequency modulation (VFM) controller, a
drive pin (EXT) for an external transistor, and feedback resistors.
The Vout pin is fixed at 2V in the IC. The output of the converter with an
inductor, a diode, a capacitor, a drive transistor, and feed–back resistors can
have an output of 30V.
VARIABLE FREQUENCY
MICROPOWER DC–to–DC
CONVERTER
SEMICONDUCTOR
TECHNICAL DATA
MC33468 Features:
• Low Quiescent Bias Current of 3.0 µA
•
•
•
•
•
High Output Voltage Accuracy of ±2.5%
5
Low Startup Voltage of 0.8 V at No Load
Output Voltage Set With External Resistors
1
Operating Temperature Range: –40°C to +85°C
Surface Mount Package
N SUFFIX
PLASTIC PACKAGE
CASE 1212
(SOT–23–5)
ORDERING INFORMATION
Device
Output
Voltage
Marking
Reel
Size
Tape
Width
Quantity
MC33468SN–20ATR
2.0
0KXX*
7”
8 mm
3000
* “XX” denotes the lot number.
PIN DESCRIPTION
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Pin No.
Symbol
1
GND
Ground
2
VDD
Input
3
EXT
External Transistor Drive
4
NC
No Connection
5
VOUT
PIN CONNECTIONS
Description
Voltage Output Pin (Fixed at 2V)
Ground
1
Vdd
2
EXT
3
5 VOUT
4 N/C
(Top View)
Representative Block Diagram
2
5
VDD
3
VOUT
Drive
EXT
Oscillator
Vref
1
MOTOROLA ANALOG IC DEVICE DATA
Gnd
1
MC33468
MAXIMUM RATINGS (TC = 25°C, unless otherwise noted.)
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Symbol
Value
Unit
Power Supply Voltage (Transient)
VDD
12
V
Power Supply Voltage (Operating)
VDD
10
V
External Pin Voltage
VEXT
–0.3 to VDD + 0.3
V
EXT Pin Source/Sink Current
IEXT
50/50
mA
150
667
mW
°C/W
Operating Junction Temperature
PD
RθJA
TJ
125
°C
Operating Ambient Temperature
TA
–40 to +85
°C
Tstg
–55 to +125
°C
Rating
Power Dissipation and Thermal Characteristics
N Suffix, Plastic Package Case 1212 (SOT–23–5)
Maximum Power Dissipation @ TA = 250°C
Thermal Resistance, Junction–to–Air
Storage Temperature Range
ELECTRICAL CHARACTERISTICS (VDD = 1.9 V, TA = 25°C, unless otherwise noted.)
Characteristic
Symbol
Min
Typ
Max
Note1
Unit
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OSCILLATOR
Frequency
fosc
–
180
–
kHz
B
Oscillator Minimum Supply Voltage (IO = 0 mA)
VDD
–
0.7
0.8
V
B
D
65
75
–
%
B
Isource
Isink
1.5
–
–
mA
C
1.5
–
–
mA
D
VOUT
IQ
1.950
2.000
2.050
V
–
15
25
µA
A
A
Oscillator Duty Cycle
EXT OUTPUT
ON State Source Current (VEXT = GND)
OFF State Sink Current (VEXT = 1.9 V)
TOTAL DEVICE
Output Voltage
Quiescent Bias Current (VOUT = 1.9 V, IO = 0 mA)
Quiescent Bias Current (VOUT = 2.1 V, IO = 0 mA)
IQ
RVout
Internal Resistor (VOUT to GND)
DVOUT
DTA
Output Voltage Temperature Coefficient
IOUT = 10 mA, –40°C ≤ TA ≤ 85°C
–
3.0
5.0
µA
2.0
–
–
MW
–
±50
–
ppm/oc
E
1. Indicates test circuits shown on next page.
Figure 1. Output Voltage versus Output Current
Figure 2. Efficiency versus Output Current
80
Vin = 3.6 V
70
35
EFFICIENCY
VOUT , OUTPUT VOLTAGE (V)
40
30
60
50
40
25
30
20
0
20
40
IOUT, OUTPUT CURRENT (mA)
60
20
Vin = 3.6 V
0
20
 Motorola, Inc. 1999
2
40
60
IOUT, OUTPUT CURRENT (mA)
Rev 1, 09/1999
MOTOROLA ANALOG IC DEVICE DATA
MC33468
A
B
VDD
VDD
VOUT
A
VOUT
A
EXT
EXT
GND
GND
Oscilloscope
C
D
VDD
VDD
VOUT
VOUT
EXT
EXT
GND
GND
E
VDD
VOUT
A
EXT
GND
Figure 3. Test Circuit Schematics
MOTOROLA ANALOG IC DEVICE DATA
3
MC33468
DEFINITIONS
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.
Since the VDD pin is connected to the input no external
startup circuit is needed.
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.
Oscillator
The oscillator frequency, is internally programmed to
180 kHz. The duty ratio of the oscillator is designed for a
constant value of 0.75 nominal. Hence the nominal on–time
of the power switch is:
0.75
D
ton
4.16 µs
f osc (180 kHz)
FUNCTIONAL DESCRIPTION
Introduction
The MC33468 is a monolithic power switching regulator
optimized for dc–to–dc converter applications where power
drain must be minimized. The MC33468 uses Variable
Frequency Modulation to step up the input DC voltage to a
higher accurate output voltage. Potential applications include
low power consumer products and battery powered portable
products. Typical application circuits are shown in Figure 4.
+
+
+
Feedback Comparator
The output voltage is sensed and fed to a high speed
comparator noninverting input through an internal resistive
divider. The comparator inverting input is connected to an
internally trimmed reference.
With a voltage mode ripple converter operating under
normal conditions, output switch conduction is initiated and
terminated by the oscillator, off–time is controlled by the high
speed voltage feedback comparator.
Operating Description
The MC33468 converter operates as a fixed on–time,
variable off–time voltage mode ripple 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
Figure 4. Typical 2.0 V Application with BJT
VOUT
VDD
VIN
VOUT
EXT
Gnd
Figure 5. Design Equations for Step–Up
Calculation
Equation
ton
D
f osc
L
t (n)(VinP ) (ton)
IL(avg)
IL(pk)
2
(V
in
*
O
Iin
V sat)(t on)
L
Vripple(pp)
[
(ton)(I )
O
(C )
O
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 directly affects regulation.
Capacitor CO should have a low equivalent series resistance (ESR).
NOTE: 1. Vsat – Saturation voltage of the switching transistor.
n – Estimated circuit efficiency.
4
MOTOROLA ANALOG IC DEVICE DATA
MC33468
Figure 6. Typical 2.0 V Application with MOSFET
VOUT
VDD
VOUT
VIN
EXT
GND
If input voltage is high enough, higher efficiency may be
obtained by using a MOSFET as the switch transistor, in
which no gate resistor or capacitor is needed.
MOSFET and BJT voltage rating (VDS and VCE) should be
high enough to allow for spikes in voltage.
Figure 7. Typical Application for Output Voltages Over 2.0 V
L1
D1
VOUT
R1
VDD
(2.0 V)
VOUT
VIN
COUT
EXT
Q1
Inductor (L1)
Diode (D1)
Capacitor (COUT)
Transistor (Q1)
Resistor (R1)
Resistor (R2)
When choosing the output capacitor, ensure that the
capacitor voltage is higher than Vout. Select an inductor with
low DC resistance and high saturation. A Schottky diode is
recommended for a lower voltage drop and faster switching.
MOTOROLA ANALOG IC DEVICE DATA
R2
GND
CD54 (15 mH)
MBRD540T1
47 mF (Tantalum type)
MMFT3055VL
150 kW
10 kW
Use external resistors that are much smaller resistance than
the resistance internal to the IC (minimum of 2 MW). When R1
is much less than the internal resistance, the error is
minimized.
5
MC33468
OUTLINE DIMENSIONS
N SUFFIX
PLASTIC PACKAGE
CASE 1212–01
(SOT–23)
ISSUE O
A
5
E
1
A2
0.05 S
B
D
NOTES:
1. DIMENSIONS ARE IN MILLIMETERS.
2. INTERPRET DIMENSIONS AND TOLERANCES
PER ASME Y14.5M, 1994.
3. DATUM C IS A SEATING PLANE.
A1
DIM
A1
A2
B
C
D
E
E1
e
e1
L
L1
4
2
L
3
E1
L1
B
C
5X
0.10
M
C B
S
A
C
S
e
e1
MILLIMETERS
MIN
MAX
0.00
0.10
1.00
1.30
0.30
0.50
0.10
0.25
2.80
3.00
2.50
3.10
1.50
1.80
0.95 BSC
1.90 BSC
0.20
–––
0.45
0.75
Recommended Footprint for Surface Mount Applications
0.7 MAX.
1.0
2.4
0.95
0.95
1.9
(Unit: mm)
SOT–23–5
6
MOTOROLA ANALOG IC DEVICE DATA
MC33468
NOTES
MOTOROLA ANALOG IC DEVICE DATA
7
MC33468
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8
◊
MC33468/D
MOTOROLA ANALOG IC DEVICE
DATA