Linear Dimensions LND34063A Dc-to-dc converter control circuit Datasheet

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DATA SHEET
LND34063A
DC-to-DC Converter Control Circuits
GENERAL DESCRIPTION
The LND34063A is a monolithic control circuit
containing the primary functions required for
DC-to-DC converters This device consist of an
internal temperature compensated reference,
comparator, controlled duty cycle oscillator
with an active current limit circuit, driver and
high current output switch. This device was
specifically designed to be incorporated in
Step-down and Step-up and Voltage-Inverting
applications with a minimum number of
external components.
FEATURES
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Operation from 3.0V to 40V Input
Low Standby Current
Current Limiting
Output Switch Current to 1.5A
Frequency Operation to 100kHz
Precision 2% Reference
PIN CONNECTIONS
Driver
Collector
Switch
Collector
Switch
Emitter
Timing
Capacitor
Ground
LND34063A
Ipk
Sense
V
CC
Comparator
Inverting
Input
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •
LND34063A
ABSOLUTE MAXIMUM RATINGS
Rating
Symbol
Value
Unit
Power Supply Voltage
Vcc
40
Vdc
Comparator Input Voltage Range
VIR
-0.3 to +40
Vdc
Switch Collector Voltage
VC(Switch)
40
Vdc
Switch Emitter Voltage(Vpin=40V)
VE(switch)
40
Vdc
Switch Collector to Emitter Voltage
VCE(switch)
40
Vdc
Driver Collector Voltage
Vc(driver)
40
Vdc
Driver Collector Current(Note 1)
Ic(driver)
100
mA
Switch Current
Isw
1.5
A
Operating Junction Temperature
TJ
+150
ºC
Operating Ambient Temperature
TA
0 to +70
ºC
Storage Temperature
Tstg
-65 to +150
ºC
SCHEMATIC DIAGRAM
8
Driver
CollectorO
1
OSwitch
Collector
1
3
2
S
Q
Q2
Q1
CR
I pk
Sense O
7
100
I
pk
2 Switch
O Emitter
3
O Timing
Capacitor
C
Oscillator T
V O6
CC
+
-
Comparator 5
Inverting O
Input
1.25 V
Reference
4
O Ground
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •
LND34063A
ELECTRICAL CHARACTERISTICS
Vcc=5.0V,TA=Tlow to Thigh, unless otherwise specified.)
Characteristics
Symbol
Min
Typ
Max
Unit
fOSC
24
33
42
kHz
Ichg
24
35
42
µA
Idischg
140
220
260
µA
Idischg/Ichg
5.2
6.5
7.5
-
Vipk(sense)
250
300
350
mV
Vce(sat)
-
1.0
1.3
V
Vce(sat)
-
0.45
0.7
V
hFE
50
75
-
-
Ic(off)
-
40
100
µA
Vth
1.225
1.21
1.25
-
1.275
1.29
V
Regline
-
1.4
5.0
mV
IIB
-
-20
-400
nA
Icc
-
-
4.0
mA
Oscillator
Frequency
(Vpin5=0V, CT=1.0nF, TA=25ºC)
Charge Current
(Vcc=5.0V to 40V, TA =25ºC)
Discharge Current
(Vcc=5.0V to 40V, TA=25ºC
Discharge to charge Current ratio
(Pin 7 to Vcc, TA =25ºC
Current Limit Sense Voltage
(Ichg=I dischg, T=25ºC
Output Switch(Note 2)
Saturation Voltage Darlington
Connection
(Isw=1.0 A, Pins 1,8 connected)
Saturation Voltage, Darlington
Connection
(Isw=1.0A, Rpin8=82Ω to Vcc,
forcedβ=20)
DC Current Gain
(Isw=1.0A, Vce=5.0V TA = 25º C
Collector Off-State Current
(Vce=40V)
Comparator
Threshold Voltage
(TA=25ºC)
(TA=Tlow to Thigh)
Threshold Voltage Line Regulation
(Vcc=3.0V to 40V)
Input Bias Current
(Vin=0V)
Total Device
Supply Current
(Vcc=5.0V to 40V, Ct=1.0nF,
Pin 7=Vcc,Vpin 5>Vth, Pin 2=Gnd,
remaining pins open)
Notes:
1. Maximum package power dissipation limits must be observed.
2. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient
temperature as possible.
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •
LND34063A
SOME TYPICAL APPLICATIONS
170µH
L
8
180
1
1
3
2
S
Q
Q2
Q1
CR
7
100
I
pk
Rsc 0.22
Oscillator T
6
V O
IN
12 V
2
C
3
100
CT
1500pf
1.25 V
Reference
+
+
-
4
5
47k
+
330
2.2k
R1
1.0 µH
V
OUT
O 28V/175mA
R2
O VOUT
+
100
Co
Optional Filter
Fig 1 : STEP UP CONVERTER
8
1
1
3
S
2
Q
8
O VOUT
1
Q2
3
2
S
I
6
pk
Oscillator
100
2
C
T
-
I
Rsc
3
O
+
Q1
7
100
Rsc
1.25 V
Reference
6
V O
IN
C
2
T
3
O
-
1.25 V
Reference
4
5
O
O
pk
Oscillator
+
4
5
O VOUT
R --> 0 for
Constant V
IN
Q2
CR
7
V O
IN
Q
Q1
CR
R
1
O
O
2a: External NPN Switch
2b: External NPN Saturated Switch
Fig 2 : External Boost Connections
for Ic Peak Greater than 1.5A
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •
LND34063A
8
1
1
3
2
S
Q
Q2
Q1
CR
7
100
I
Rsc 0.33
V O
IN
25 V
pk
2
C
Oscillator T
6
3
+
100
CT
470pf
1.25 V
Reference
+
-
220µH
L
4
5
V
OUT
O 5.0V/500mA
R2
3.6k
+
470
1.2k
R1
1.0 µH
O VOUT
+
100
Co
Optional Filter
Fig 3 : STEP DOWN CONVERTER
8
8
1
1
1
1
3
S
2
Q
3
Q2
S
2
Q1
CR
I
V O
IN
Q1
CR
100
100
6
O VOUT
Q2
7
7
Rsc
Q
pk
C
Oscillator
2
3
O
+
-
I
pk
Rsc
T
O VOUT
6
V O
IN
-
3
1.25 V
Reference
4
5
4
5
2
T
O
+
1.25 V
Reference
O
O
C
Oscillator
O
O
4b: External NPN Saturated Switch
4a: External NPN Switch
Fig4 : External Boost Connections
for Ic Peak Greater than 1.5A
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •
LND34063A
8
1
1
3
2
S
Q
Q2
Q1
CR
7
100
I
Rsc 0.33
C
Oscillator T
6
V O
IN
25 V
2
pk
3
100
CT
470pf
1.25 V
Reference
+
+
-
220µH
L
4
5
3.6k
R1
1.0 µH
V
OUT
O 5.0V/500mA
R2
+
470
1.2k
O VOUT
+
100
Co
Optional Filter
Fig 5 : VOLTAGE INVERTING CONVERTER
8
1
1
3
2
S
Q
8
I
pk
Oscillator
2
C
T
-
I
Rsc
3
1.25 V
Reference
O VOUT
6
V O
IN
pk
Oscillator
Q1
2
C
T
3
O
+
-
4
5
1.25 V
Reference
4
5
O
O
O VOUT
Q2
100
O
+
Q
7
100
6
S
CR
7
Rsc
3
2
Q1
CR
V O
IN
1
1
Q2
O
O
6a: External NPN Switch
6b: External NPN Saturated Switch
Fig6 : External Boost Connections
for Ic Peak Greater than 1.5A
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •
LND34063A
Figure 7: 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)
( Vout|+VF ) / (Vin -Vsat )
(tON/tOFF)
max
1/ f MIN
1/ f MIN
1/ f MIN
CT
4.0 x 10 ton
4.0 x 10 ton
4.0 x 10 ton
IPK(switch)
2 Iout (max)(ton/toff + 1)
2 Iout(max)
2 Iout (max)(ton/toff + 1)
RSC
0.3 / Ipk(switch)
0.3 / Ipk(switch)
0.3 / Ipk(switch)
L(min)
(Vin(min) –Vsat )/(Ipk(switch))=tout(max)
(Vin(min) – Vsat -Vout ) /
(Ipk(switch)) = tout(max)
(Vin(min) –Vsat ) / (Ipk(switch)) =
tout(max)
CO
9(Ioutt on) / (Vripple(pp))
Ipk(switch) (ton + toff) / 8V ripple(pp)
9(Ioutt on) / (Vripple(pp))
-5
-5
-5
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, |Vout |=1.25 (1 +R2 / R1)
IOUT-Desired output current
fmin-Minmum desired output switching frequency at the selected values of VIN and IO
Vripple(p-p)- Desired peak-to-peak output ripple voltage. In pratice, 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.
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •
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