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TDA4605
CONTROL CIRCUIT FOR SWITCH MODE
POWER SUPPLIES USING MOS TRANSISTORS
■Fold-Back Characteristic provides Overload
Protec tion for External Diodes
■Burst Operation under Short-Circuit and no
Load Condit ion s
■Loop Error Protection
■Switch-off in case of too low Line Voltage
(Under Voltage Switch-of f)
■Line Vo ltage Comp ens ation of Overload Point
■Soft-Start for smooth Start-up
■Chip Over-Temperature Protection (Thermal
Shutdown)
■On-Chip Parasitic Transformer Oscillation
Suppres sion Ci rcuitry
■Decrease of Regulated Voltage for low Power
Consumption
DESCRIPTION
The IC TDA4605 controls the MOS Power Tran-
sistor and performs all necessary regulation and
monitoring functions in free running flyback con-
verters. Since good load regulation over a wide
load range is attained, this IC is particul arly suita-
ble for Consumer as well as Industrial Power Sup-
plies.
Alternative s ource of the TDA4605 is als o availa-
ble from SIEMENS Semiconductors Consumer
Electronics A.G.
Figure 1. Pin Connections
DIP28
(Plastic Package )
ORDER CODE: TDA4605
SO8
(Plastic Micropa ckag e)
ORDER CODE: TDA4605D
1
2
3
4
8
7
6
5
REGULATION INPUT
PRIMARY CURRENT SIMULATION
PRIMARY VOLTAGE MONITORING
GROUND OUTPUT
SUPPLY VOLTAGE
SOFT-START
ZERO CROSSING DETECTOR INPUT
4605-01.eps
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PIN CONFIGURATION
Figu re 2. Blo ck D ia gra m
Pin
Number Description
1
Regulating voltage : information input concerning secondary voltage.
By comparing the regulating voltage obtained from the regulating winding of the transformer with the
internal reference voltage, the output pulse width on Pin 5 is adapted to the load of the secondary side
(normal, overload, short circuit, no load)
2
Primary current simulation : information input regarding the primary current. The primary current rise in the
primary winding is simulated at Pin 2 as a voltage rise by means of external RC element. When a value is
reached that is derived from the regulating voltage at Pin 1, the output pulse at Pin 5 is terminated. The RC
element serves to set the maximum power at the overload point.
3Primary voltage detector : input for primary voltage monitoring. When the line voltage is too low the IC is
switched-off by comparing V3 with an internal reference. Voltage at Pin 3 is used for overload point
compensation.
4 Ground
5 Output : push-pull output for charge and discharge of the gate capacitance of the power MOS transistor.
6
Supply voltage : Supply voltage input. From it are derived a stable internal reference voltage (VREF) and the
switching thresh old V6A, V6E, V6 max and V6 min for the supply voltage detector.
if V6 > V6E the VREF is switched on and switched off when V6 < V6A. In addition the logic is only enable for
V6 min < V6 < V6 max.
7Soft-start : input for soft-start and integration network. Start-up will begin with short pulses by connecting a
capacitor between Pin 7 to ground. This capacitor together with a resistor connected between Pin 7 and
error amplifier output also as acts an integrator network for regulation.
8Zero detector : Input for the oscillator feedback. After starting oscillator, every zero transit of the feedback
voltage (falling edge) triggers an output pulse at Pin 5. The trigger threshold is at typically - 50mV
1
2
3
4
56
7 8
V
6min
V
6max
V
6E
V
6A
V
2B
V
st
V
R
V
u
V
REF
Reference
Voltage
(typ. 3V)
Supply
Voltage
Monitor
Primary
Current
Recopy
Output Stage
and
Current Limit
Logic
Starting
Impulse
Generator
Regulating
& Overload
Amplifier
Current
Source
Overload
Point
Correction
Low Voltage
Protection
Monitoring
Stop
Comp.
Zero
Crossing
Detector
TDA4605
4605-02.eps
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ABSOLUTE MAXIMUM RATI NGS
THE RMAL DATA
ELECTRICAL CHARACTERISTICS (VCC = 10V, Tamb = 25oC, unless otherwise specified)
Symbol Parameter Pin Value Unit
V1
Supply Voltage
1 -0.3, +3 V
V22 -0.3 V
V33 -0.3 V
V44 -0.3 V
V66 -0.3, +20 V
V77 -0.3 V
I1
Supply Current
13mA
I
223mA
I
333mA
I
4t
p
≤
50µs, V ≤ 0.1 4 - 1.5 A
I5tp ≤ 50µs, V ≤ 0.1 5 -0.5, +1.5 A
I6tp ≤ 50µs, V ≤ 0.1 6 0.5 A
I773mA
I
88 -3, +3 mA
TjJunction Temperature (autom. thermal disjunction) +125 oC
Tstg Storage Temperature -40, +125 oC
Symbol Parameter Value Unit
Rth(j-a) Junction-ambient Thermal Resistance 80 oC/W
Rth(j-c) Junction-case Thermal Resistance 45 oC/W
Tamb Ambient Temperature -20, +85 oC
Symbol Parameter Test Conditions Min. Typ. Max. Unit
START-UP HYSTERESIS
I6E0 Start-up Current Drain V6 = V6E 0.6 0.8 mA
V6E Switch-on Voltage 11 12 13 V
V6A Switch-off Voltage 4.5 5 5.5 V
I6E1 Switch-on Curre nt V6 = V6E 11 mA
I6A1 Switch-off Current V6 = V6A 10 mA
VOLTAGE CLAM P (V6 = 10V, IC Switched off)
V2(Max.) At Pin 2 (V6 < V6E)I
2 = 1mA 5.6 6.6 9 V
V3(Max.) At Pin 3 (V6 < V6E)I
3 = 1mA 5.6 6.6 9 V
CONTROL RANGE
V1R Control Input Voltage 400 410 420 mV
-VRVoltage Gain of the Control Circuit in the Control Range VR = d(V2S - V2B)/dV1
f = 1kHz 43 dB
PRIMARY CURRENT SIMULATION VOLTAGE
V2B Basic Value 0.955 1.00 1.03 V
OVERLOAD RANGE AND SHORT CIRCUIT OPERATION
V2O Peak Value in the Range of Secondary Overload V1 = V1R - 10mV 2.8 2.95 3.1 V
DV2Maximum Ramp Amplitude V2O - V2B 1.82 1.95 2.08 V
V2S Peak Value in the Range of Secondary Short
Circuit Operation V1 = 0 2.3 2.5 2.7 V
FOLDBACK POINT CORRECTION
-I2Foldback Point Corre ction Curre nt V3 = 3.7V 300 500 650 µA
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ELECTRICAL CHARACTERISTICS (VCC = 10V, Tamb = 25oC, unless otherwise specified) - Continued
Symbol Parameter Test Conditions Min. Typ. Max. Unit
GENERALLY VALID DATA (V6 = 10V)
VOLTAGE OF THE ZERO Transition DETECTOR
V8P Positive Clamping Voltage I8 = 1mA 0.75 V
V8N Negative Clamping Voltage I8 = -1mA -0.2 V
V8S Threshold Value 40 50 mV
TUL Suppressi on of Tr ansfo rmer Ringin g 3 3 .8 4.5 µs
-I8Input Current V8 = 0 0 4 µV
PUSH-PULL OUTPUT STAGE
SATURATION VOLTAGES
VSatU Pin 5 Sourcing I5 = -0.1A 1.5 2.0 V
VSatU Pin 5 Sinking I5 = 0.1A 1.0 1.2 V
VSatU Pin 5 Sinking I5 = 0.5A 1.4 1.8 V
OUTPUT SLOW RATE
dV5/dt Rising Edge 70 V/µs
-dV5/dt Falling Edge 100 V/µs
REDUCTION OF CONTROL VOLTAGE
-I1Current to reduce the Control Voltage V7 = 1V 50 µA
PROTECTION CIRCUIT
V6(Min.) Undervoltage Protection for V6 :
Voltage at Pin 5 = V5(Min.) if V6 < V6(Min.) 7.0 7.25 7.5 V
V6(Max.) Overvoltage Protection for V6 :
Voltage at Pin 5 = V5(Min.) if V6 > V6(Max.) 15 16 16.5 V
V3A Undervoltage Protection for VAC :
Voltage at Pin 5 = V5(Min.) if V3 < V3A V2 = 0V 970 1005 1040 mV
Oj Over Temperature : at the given chip temperature the
IC will switch V5 to V5(Min.) 150 oC
V3Sat Voltage at Pin 3 if one of the protection functions was
triggered ; (V3 will be clamped until V6 < V6A)I3 = 750µA 0.4 0.8 V
I6Current Drain during Burst Operation V3 = V2 = 0V 8 mA
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FUNCTIONAL DESCRIPTION
In free running fly-back converters, the TDA4605
assumes control of a MOS power t ransistor and all
necessary regulation and monitoring functions.
The serial circuit of power transistor and primary
winding of t he flyback tr ansformer is co nnected t o
the input voltage. During the switch-on period of
the transistor, energy is stored in the transformer
and during the switch-off period it i s fed t o t he l oad
via the secondary winding. By varying the switch-
on time of the power transistor, the IC controls
each portion of energy transferred to the second-
ary side such that the out put voltage remains near-
ly independent of load variations.
The required cont rol information is taken from th e
input voltage during t he switch-on period and from
a regulation winding during the switch-off peri od. A
new cycle begins as soon as the energy stored in
the transformer has been totally delivered to the
secondary side.
In different load ranges, the SMPS wi ll behave as
follows:
– No-Load Operation: The power supply unit os-
cillates in non continuous m ode at a typical fre-
quency of 20 to 40kHz. Dependi ng upon the
transformer winding and the regulated voltage di-
vider, the output voltage can be slightly above
the nominal value.
– Norm a l Operati on: S tarting from typ. 200kHz,
the switching frequency falls with increasing load
and decreasin g AC voltage. The duty cycle de-
pends primaril y on the AC voltage. The output
voltage is only slightly load-dependent.
– Overload Point: Maximu m ou tput pow er is
available at this point of the output characteri s-
tics
– Overload: The energy transferred per operation
cycle is limited at the top. Therefore, the output
voltage will fall with secondary overloading .
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PACKAG E MECHANICAL DATA
8-PINS - PLAS TI C DIP
Figure 3. 8-Pin Package
8-PINS - PLAS TIC SO
Figure 4. 8-Pin Plasti c Micropackage
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