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DC-DC Converter Control Circuits
MC34063A
FEATURES
● OUTPUT SWITCH CURRENT IN EXCESS OF 1.5A
● 2% REFERENCE ACCURACY
● LOW QUIESCENT CURRENT:2.5mA(TYP.)
● OPERATING FROM 3V TO 40V
● FREQUENCY OPERATION TO 100KHz
● ACTIVE CURRENT LIMITING
● MOISTURE SENSITIVITY LEVEL 3
● MC34063AG is Halogen Free products
8 SOP/ 8 DIP PIN Configulation
SOP-8 PKG
DIP-8 PKG
APPLICATION
● Battery Chargers
● NICs / Switches / Hubs
● ADSL Modems
● Negative Voltage Power Supplies
Switch
Collector
1
Switch
Emitter
2
Timing
Capacitor
3
Ground 4
Driver
8 Collector
7 Ipk Sense
6 Vcc
5
Comparator
Inverting
Input
DESCRIPTION
ORDERING INFORMATION
Device
Package
MC34063AD
MC34063AGD
SOP-8
MC34063AN
DIP-8
The MC34063A series is a monolithic control circuit delivering the main functions for DC-DC voltage
converting.
The device contains an intermal temperature compensated reference, comparator, duty cycle controlled
oscillator with an active current limit circuit driver and high current output switch.
Output voltage is adjustable through two external resistors with a 2% reference accuracy.
Employing a minimum number of external components the MC34063A devices series is designed for
Step-Down, Step-Up and Voltage-lnverting applications.
May. 2009 - Rev. 1.2
−1−
HTC
DC-DC Converter Control Circuits
MC34063A
TYPICAL ELECTRICAL CHARACTERISTICS (Continued)
Reference Voltage vs Temperature
Bias Current vs Temperature
Vref
(V)
1.265
1.260
1.255
1.250
1.245
1.240
-40
VCC=5V
0 40 80 120 TJ(℃)
IBias
(㎁)
10
8
6
4
2
0
-40
VCC=5V
CII to GND
0 40 80 120 TJ(℃)
Supply Current vs Temperature
ICC
(㎃)
5
4
3
2
1
0
-40
VCC=5V
CT=1㎋
0 40 80 120 TJ(℃)
Supply Current vs Input Voltage
ICC
(㎃)
4.0
3.5
3.0
2.5
2.0
1.5
0
TJ= 25℃
CT= 1㎋
10 20 30 40 Vin(V)
May. 2009 - Rev. 1.2
−5−
HTC
DC-DC Converter Control Circuits
MC34063A
Design Formula Table
Calculation
Step-Up
Step-Down
Voltage-Inverting
ton/toff
Vout + VF - Vin(min)
Vin(min) - Vsat
Vout + VF
Vin(min) - Vsat
|Vout| + VF
Vin + Vsat
(ton/toff)max
CT
Ipk(switch)
Rsc
1
fmin
4.0 X 10-5 ton
( )2Iout(max)
ton
toff
+1
0.3 / Ipk(switch)
1
fmin
4.0 X 10-5 ton
2Iout(max)
0.3 / Ipk(switch)
1
fmin
4.0 X 10-5 ton
( )2Iout(max)
ton
toff
+1
0.3 / Ipk(switch)
L(min)
Vin(min) - Vsat
( ) ( ) ( )Ipk(switch)
x ton(max)
Vin(min)-Vsat-Vout
Ipk(switch)
x ton(max)
Vin(min) - Vsat
Ipk(switch)
x ton(max)
Co
9
Iout ton
Vripple(pp)
Ipk(switch)(ton + toff)
8Vripple(pp)
9
Iout ton
Vripple(pp)
TERMS AND DEFINITIONS
Vsat - Saturation voltage of the output switch.
VF - Forward voltage drop of the output rectifier.
The following power supply characteristics must be chosen:
Vin - Nominal input voltage.
Vout - Desired output voltage.
Iout - Desired output current.
fmin- Minimum desired output switching frequency at the selected values of Vin and IO.
Vripple(p-p) – Desired peack-to-peack output ripple voltage. In practice the calculated capacitor value will need
to be increased due to its equivalent series resistance and board layout. The ripple voltage should
be kept to a low value since it will directly affect the line and load regulation.
May. 2009 - Rev. 1.2
− 11 −
HTC