LYT0002/0004-0006
LYTSwitch-0 Off-Line Low Power
LED Driver IC Family
www.power.com June 2015
Lowest Component Count, Off-Line Switcher IC
for Non-Isolated LED Lighting Applications
This Product is Covered by Patents and/or Pending Patent Applications.
Figure 1. Typical Application Schematic (a) Buck, (b) Buck-Boost.
Product Highlights
• High power factor meeting EU and USA requirements
• Very low component count
• Frequency jitter reduces EMI
• No bias supply or transformer required
Cost-Effective LED driver
The LYTSwitch-0 family parts are a highly integrated combination
of controller, driver and switching power MOSFET that enable low
component-count, non-isolated switching topologies for highly
cost competitive LED lighting applications.
66 kHz operation together with frequency jittering insures a very
low-cost EMI filter. Less than <50 ms start-up time turn-on
without overshoot, improves end user experience – no delay.
Power Factor Correction
Allows designs that easily meet European and North American
standards for PFC in consumer lighting applications.
Tight CC Performance
Accurate current limit with tight line and load regulation that is
stable over a wide temperature range makes the LYTSwitch-0
ideal for LED lighting applications.
Comprehensive Protection
Integrated auto-restart for short-circuit, open-circuit and open-
loop faults as well as a high threshold over-temperature
protection feature (min. 135 °C) with automatic restart provide
extensive protection at no additional cost.
LYTSwitch-0 Supports Different LED Applications
Flyback, buck, buck-boost and boost architectures are all
supported by the LYTSwitch-0 family. The 700 V switching power
MOSFET supports an input voltage range of 85 VAC to 308 VAC.
Description
The LYTSwitch™-0 family is specifically designed for low cost
LED bulb replacement applications. LYTSwitch-0 devices
integrate a 700 V power MOSFET, oscillator, simple ON/OFF
control scheme, a high-voltage switched current source,
frequency jittering, cycle-by-cycle current limit and thermal
shutdown circuitry into a monolithic IC.
The start-up and operating power are derived directly from the
voltage on the DRAIN pin. This eliminates the need for a bias
supply and associated circuitry plus allowing low-cost discrete
inductors to be used. The fully integrated auto-restart circuit in
the LYTSwitch-0 family safely limits output power during fault
conditions such as short-circuit or open-loop, reducing component
count and lower system cost. Package options for thru-hole and
surface-mount suit different manufacturing requirements.
Output Current Table1
Product6PF4,5 230 VAC ±15% 85-308 VAC
MDCM2CCM3MDCM2CCM3
LYT0002D/P High 45 mA 65 mA 30 mA 40 mA
Low 63 mA 80 mA 63 mA 80 mA
LYT0004D/P High 85 mA 110 mA 50 mA 70 mA
Low 98 mA 139 mA 98 mA 139 mA
LYT0005D/P High 100 mA 140 mA 60 mA 90 mA
Low 120 mA 170 mA 120 mA 170 mA
LYT0006D/P High 165 mA 220 mA 100 mA 140 mA
Low 200 mA 280 mA 200 mA 280 mA
Table 1. Output Current Table.
Notes:
1. Typical output current in a non-isolated buck converter. See Key Applications
Considerations section for more information.
2. MDCM – mostly discontinuous mode.
3. CCM – continuous conduction mode.
4. PF high: >0.7 @ 120 VAC and >0.5 @ 230 VAC.
5. PF low: for non-PF application where CIN >5 mF minimum.
6. Packages: P: PDIP-8B, D: SO-8C.
(a)
(b)
PI-6810-060613
FB BP
S
D
VIN
LYTSwitch-0
VIN
PI-6819a-060613
+
FB BP
S
D
LYTSwitch-0
Figure 2. Package Options.
SO-8C (D Package) PDIP-8B (P Package)
Rev. B 06/15
2
LYT0002/0004-0006
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Table 2. Common Circuit Configurations Using LYTSwitch-0 for Driving LEDs.
Topology Basic Circuit Schematic Key Features
High-Side
Buck –
Direct
Feedback
• Output referenced to input
• Positive output (VO) with respect to -VIN
• Step down – VO < VIN
• Low cost direct feedback (±5% typ.)
Low-Side
Buck –
Constant
Current LED
Driver;
Optocoupler
Feedback
• Output referenced to input
• Negative output (VO) with respect to +VIN
• Step down – VO < VIN
• Optocoupler feedback
• Low-cost non-safety rated optocoupler
• Optional Zener provides disconnected load
protection
• Accuracy determined by VF variation of
optocoupler LED
High-Side
Buck-Boost –
Constant
Current LED
Driver
• Output referenced to input
• Negative output (VO) with respect to +VIN
• Step up/down – VO > VIN or VO < VIN
• Low-cost direct feedback (±5% typ.)
• Fail-safe – output is not subjected to input voltage
if the internal power MOSFET fails
• Ideal for driving LEDs – better accuracy and
temperature stability than low-side Buck constant
current LED driver
Low-Side
Boost –
Constant
Current LED
Driver
• Output referenced to input
• Positive output (VO) with respect to -VIN
• Step up – VO > VIN
• Low-cost direct feedback (±5% typ.)
• Ideal for driving high-voltage LEDs string – good
accuracy and temperature stability
Low-Side
Flyback –
Constant
Current LED
Driver
• Output referenced to input
• Positive output (VO) with respect to -VIN
• Step down – VO < VIN
• Low-cost direct feedback (±5% typ.)
• Fail-safe – output is not subjected to input voltage
if the internal power MOSFET fails
• Ideal for driving very low voltage LEDs string –
• good accuracy and temperature stability
VIN
PI-7043-053113
+
FB BP
SD
LYTSwitch-0
VIN
PI-7046-053113
+
LYTSwitch-0
D
S
FB
BP
VIN
PI-7047-060313
+
LYTSwitch-0
D
S
FB
BP
PI-7044-060313
+
+
BP FB
D S
VIN
IO
R =
VF
VF
IO
LYTSwitch-0
VIN
PI-7045-060313
FB BP
SD
RSENSE IO
LYTSwitch-0
Rev. B 06/15
3
LYT0002/0004-0006
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Figure 3a. Functional Block Diagram LYT0002.
PI-2367-032213
CLOCK
JITTER
OSCILLATOR
5.8 V
4.85 V
SOURCE
(S)
S
R
Q
DCMAX
BYPASS
(BP)
FAULT
PRESENT
+
-
VILIMIT
LEADING
EDGE
BLANKING
THERMAL
SHUTDOWN
+
-
DRAIN
(D)
BYPASS PIN
UNDERVOLTAGE
CURRENT LIMIT
COMPARATOR
FEEDBACK
(FB)
Q
6.3 V
RESET
AUTO-
RESTART
COUNTER
1.65 V -VT
CLOCK
REGULATOR
5.8 V
Figure 3b. Functional Block Diagram LYT0004-0006.
PI-3904-032213
CLOCK
JITTER
OSCILLATOR
5.8 V
4.85 V
SOURCE
(S)
S
R
Q
DCMAX
BYPASS
(BP)
+
-
VILIMIT
LEADING
EDGE
BLANKING
THERMAL
SHUTDOWN
+
-
DRAIN
(D)
REGULATOR
5.8 V
BYPASS PIN
UNDERVOLTAGE
CURRENT LIMIT
COMPARATOR
FEEDBACK
(FB)
Q
6.3 V
1.65 V -VT
Rev. B 06/15
4
LYT0002/0004-0006
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Pin Functional Description
DRAIN (D) Pin:
Power MOSFET Drain connection. Provides internal operating
current for both start-up and steady-state operation.
BYPASS (BP) Pin:
Connection point for a 0.1 mF external bypass capacitor for the
internally generated 5.8 V supply.
FEEDBACK (FB) Pin:
During normal operation, switching of the power MOSFET is
controlled by this pin. Power MOSFET switching is terminated
when a current greater than 49 mA is delivered into this pin.
SOURCE (S) Pin:
This pin is the power MOSFET source connection. It is also the
ground reference for the BYPASS and FEEDBACK pins.
LYTSwitch-0 Functional Description
LYTSwitch-0 combines a high-voltage power MOSFET switch
with a power supply controller in one device. Unlike conventional
PWM (pulse width modulator) controllers, LYTSwitch-0 uses a
simple ON/OFF control to regulate the output voltage. The
LYTSwitch-0 controller consists of an oscillator, feedback (sense
and logic) circuit, 5.8 V regulator, BYPASS pin undervoltage circuit,
over-temperature protection, frequency jittering, current limit
circuit, leading edge blanking and a 700 V power MOSFET. The
LYTSwitch-0 incorporates additional circuitry for auto-restart.
Oscillator
The typical oscillator frequency is internally set to an average of
66 kHz. Two signals are generated from the oscillator: the
maximum duty cycle signal (DCMAX) and the clock signal that
indicates the beginning of each cycle.
The LYTSwitch-0 oscillator incorporates circuitry that introduces
a small amount of frequency jitter, typically 4 kHz peak-to-peak,
to minimize EMI emission. The modulation rate of the frequency
jitter is set to 1 kHz to optimize EMI reduction for both average
and quasi-peak emissions. The frequency jitter should be
measured with the oscilloscope triggered at the falling edge of
the Drain waveform. The waveform in Figure 5 illustrates the
frequency jitter of the LYTSwitch-0.
Feedback Input Circuit
The feedback input circuit at the FEEDBACK pin consists of a
low impedance source follower output set at 1.65 V. When the
current delivered into this pin exceeds 49 mA, a low logic level
(disable) is generated at the output of the feedback circuit. This
output is sampled at the beginning of each cycle on the rising
edge of the clock signal. If high, the power MOSFET is turned
on for that cycle (enabled), otherwise the power MOSFET remains
off (disabled). Since the sampling is done only at the beginning
of each cycle, subsequent changes in the FEEDBACK pin
voltage or current during the remainder of the cycle are ignored.
5.8 V Regulator and 6.3 V Shunt Voltage Clamp
The 5.8 V regulator charges the bypass capacitor connected to
the BYPASS pin to 5.8 V by drawing a current from the voltage
on the DRAIN, whenever the power MOSFET is off. The BYPASS
pin is the internal supply voltage node for the LYTSwitch-0.
When the power MOSFET is on, the LYTSwitch-0 runs off of the
energy stored in the bypass capacitor. Extremely low power
consumption of the internal circuitry allows the LYTSwitch-0 to
operate continuously from the current drawn from the DRAIN
pin. A bypass capacitor value of 0.1 mF is sufficient for both
high frequency decoupling and energy storage.
BYPASS Pin Undervoltage
The BYPASS pin undervoltage circuitry disables the power
MOSFET when the BYPASS pin voltage drops below 4.85 V.
Once the BYPASS pin voltage drops below 4.85 V, it must rise
back to 5.8 V to enable (turn-on) the power MOSFET.
Over-Temperature Protection
The thermal shutdown circuitry senses the die temperature.
The threshold is set at 142 °C typical with a 75 °C hysteresis.
When the die temperature rises above this threshold (142 °C)
the power MOSFET is disabled and remains disabled until the
die temperature falls by 75 °C, at which point it is re-enabled.
Current Limit
The current limit circuit senses the current in the power
MOSFET. When this current exceeds the internal threshold
(ILIMIT), the power MOSFET is turned off for the remainder of that
cycle. The leading edge blanking circuit inhibits the current limit
comparator for a short time (tLEB) after the power MOSFET is
turned on. This leading edge blanking time has been set so
that current spikes caused by capacitance and rectifier reverse
recovery time will not cause premature termination of the
switching pulse cycle.
Auto-Restart (LYT0004-0006)
In the event of a fault condition such as output overload, output
short, or an open loop condition, LYTSwitch-0 enters into
auto-restart operation. An internal counter clocked by the
oscillator gets reset every time the FEEDBACK pin is pulled
PI-6899-060613
3b
D Package (SO-8C)
BP
FB
D
1
2
4
8
7
6
5
S
S
S
S
3a
FB D
S
BP
S
S
S
P Package (PDIP-8B)
8
5
7
1
4
2
3
Figure 4. Pin Configuration.
Rev. B 06/15
5
LYT0002/0004-0006
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high. If the FEEDBACK pin is not pulled high for 50 ms, the
power MOSFET switching is disabled for 800 ms. The auto-
restart alternately enables and disables the switching of the
power MOSFET until the fault condition is removed.
Applications Example
A 6 W (Output) Universal Input Buck LED Driver Converter
The circuit shown in Figure 6 is a typical implementation of a
non-isolated, power factor corrected buck power supply for
LED driver applications. The simplicity and low component
count make this ideal for space constrained, cost sensitive
designs such as GU10 or A19 size lamps. This design was
optimized to drive an LED string at a voltage of 54 V with a
constant current of 110 mA, giving 6 W of output power. The
design operates over a universal input range from 90 VAC to
265 VAC and achieves an output current tolerance of < ±5%
at nominal line voltage. The input capacitance (C1 + C2) was
reduced to achieve the highest possible power factor input
Figure 5. Frequency Jitter.
600
0 20
68 kHz
64 kHz
VDRAIN
Time (µs)
PI-3660-081303
500
400
300
200
100
0
while still meeting conducted EMI limits. Power factor is >0.5
at 230 VAC and >0.7 PF at 120 VAC meeting requirements for
LED lamps in Europe and USA.
The input stage comprises fusible resistor RF1, bridge rectifier
BR1, capacitors C1 and C2, and inductor L1. Resistor RF1 is a
flame proof, fusible, wire wound resistor. It accomplishes
several functions: a) Inrush current limitation to below specification
of BR1; b) Differential mode conducted EMI noise attenuation; c)
Fuse should any other component fail short-circuit; d) Higher
power factor. Capacitor C1, C2 and inductor L1 forms a π filter
to reduce differential mode EMI. Capacitor C2 provides local
decoupling for the switching current through U1. There is an
optional parallel resistor on the board across L1 which damps
the resonance of the pi filter.
The power processing stage is formed by the integrated
MOSFET switch within LYT0006 (U1), a free-wheeling diode
(D1), sense resistor (R2), power inductor (L2) and output
capacitor (C5). To reduce reverse recovery losses in D1 the
value of L2 was designed such that the converter operates in
mostly discontinuous conduction mode. Diode D1 is an
ultrafast diode with a reverse recovery time (tRR) ≈35 ns. This
recovery is recommended due to the high ambient operating
time temperature which will increase diode reverse recovery
charge. A bobbin based EE10 core size indictor was selected
for L2 in order to prevent changes in inductance value when
placed inside a metal enclosure. Lower cost drum core or dog
bone inductor types may also be used, however these have an
open magnetic path which can be shorted by a metal enclosure.
This reduces the effective inductance and requires the value to
be adjusted to take this into account when placed inside the
final enclosure.
Capacitor C5 is the output filter capacitor; its primary function is
to limit the output current ripple and ensures high frequency
currents flow within as small as a loop area as possible to
reduce EMI.
PI-6998f-061313
R1
4.7 kΩ
C4
22 µF
16 V
C3
100 nF
25 V
L1
4.7 mH
C1
47 nF
630 V
C2
330 nF
450 V
RTN
54 V, 110 mA
RF1
4.7 Ω
L2
5
BR1
MB6S
600 V
L
N
90 - 265
VAC
D
FB BP
S
+
C5
47 µF
63 V
4
R2
18.7 Ω
1%
LYTSwitch-0
U1
LYT0006P
D1
MURS160T3G
RV1*
275 VAC
*Optional <1 kV Surge Requirements
Figure 6. Universal Input, 54 V, 110 mA Constant Current Power Supply using LYTSwitch-0.
Rev. B 06/15
6
LYT0002/0004-0006
www.power.com
The output current is regulated via the voltage across R2 during
the free-wheeling period when the internal MOSFET of U1 is off.
This voltage is filtered by capacitor (C4) and fed into the
FEEDBACK pin of U1. Regulation is maintained by skipping
switching cycles. As the output current rises, the voltage on
the FEEDBACK pin will rise. If this exceeds VFB then subsequent
cycles will be skipped until the voltage reduces below VFB.
Open-loop protection is provided via the auto-restart function.
If no cycles are skipped during a 50 ms period LYTSwitch-0 will
enter auto-restart (LYT0004-0006), limiting the average output
power to approximately 6% of the maximum overload power.
The auto-restart function requires the value of C3 to be 100 nF
or greater such that the IC remains operational from half-line
cycle to half-line cycle.
For disconnected LED protection an optional Zener (not shown)
can be placed across the output. This will fuse short-circuit
and prevent the output voltage rising.
Key Application Considerations
LYTSwitch-0 Design Considerations
Output Current Table
Data sheet maximum output current table (Table 1) represents
the maximum practical continuous output current for both
mostly discontinuous conduction mode (MDCM) and continuous
conduction mode (CCM) of operation that can be delivered
from a given LYTSwitch-0 device under the following assumed
conditions:
1. Buck converter topology.
2. The minimum DC input voltage is equal to voltage output.
3. For CCM operation a KRP* of 0.4.
4. Output voltage of 54 VDC.
5. Efficiency of 90%.
6. A catch/free-wheeling diode with tRR ≈35 ns is used.
7. The part is board mounted with SOURCE pins soldered to a
sufficient area of copper to keep the SOURCE pin tempera-
ture at or below 100 °C.
*KRP is the ratio of ripple to peak inductor current.
LYTSwitch-0 Selection and Selection Between
MDCM and CCM Operation
Select the LYTSwitch-0 device, free-wheeling diode and output
inductor that gives the lowest overall cost. In general, MDCM
provides the lowest cost and highest efficiency converter. CCM
designs require a larger inductor and ultrafast (tRR ≈35 ns)
free-wheeling diode in all cases. It is lower cost to use a larger
LYTSwitch-0 in MDCM than a smaller LinkSwitch-0 in CCM
because of the additional external component costs of a CCM
design. However, if the highest output current is required, CCM
should be employed following the guidelines below.
Topology Options
LYTSwitch-0 can be used in all common topologies, with or
without an optocoupler and reference to improve output voltage
tolerance and regulation. Table 2 provide a summary of these
configurations.
Component Selection
Referring to Figure 6, the following considerations may be
helpful in selecting components for a LYTSwitch-0 design.
Optional Varistor (RV1)
The Metal Oxide Varistor (RV1) is used to suppress the line
surge in order to meet IEC61000-4-5 (differential input line
1.2/50 ms and differential ring wave input line surge). A MOV is
recommended for high PF designs with surge levels of 1 kV or
greater. High PF design requires lower input capacitance values
giving a greater voltage rise across limited input capacitance
during surge events. A MOV is typically not required if the
design will use high-input capacitance (mF’s vs. nF’s) (non-PF
application).
Input Capacitance C1 and C2
Use a film capacitor if the input capacitance is less than 1 mF.
Make sure that the RMS current rating is not exceeded especially
if planning to use electrolytic capacitor. For universal or high-
line only input design use 400 V or 630 V rated capacitors, and
for low-line only use 250 V rated capacitors for lower cost and
smaller size.
Free-wheeling Diode D1
Diode D1 should be an ultrafast type. For MDCM, reverse
recovery time of ≤75 ns should be used in designs where the
diode temperature is 70 °C or below. Slower diodes are not
acceptable, as continuous mode operation will always occur
during start-up, causing high leading edge current spikes,
terminating the switching cycle prematurely, and preventing the
output from reaching regulation. If the diode temperature is
above 70 °C then a diode with a reverse recovery time of ≤35 ns
should be used.
For CCM an ultrafast diode with reverse recovery time ≤35 ns
should be used. Slower diodes cause excessive leading edge
current spikes, terminating the switching cycle prematurely and
preventing full power delivery.
Standard plastic or fast (tRR >75 ns) diodes should never be
used as the large reverse recovery currents can cause
excessive power dissipation in the diode and/or exceed the
maximum drain current specification of LYTSwitch-0.
Inductor L1
Choose any standard off-the-shelf inductor that meets the
design requirements. A “drum” or “dog bone” “I” core inductor
is recommended with a single ferrite element due to its low-cost
and very low audible noise properties. The typical inductance
value and RMS current rating can be obtained from the
LYTSwitch-0 PIXls design spreadsheet. The PIXls application is
part of the PI Expert design suite available for free download
from Power Integrations. Choose L1 greater than or equal to
the typical calculated inductance.
Note that the open magnetic path of non-shielded discrete
inductors may cause inductance value changes when placed
within metal enclosure requiring a larger value to be used.
Rev. B 06/15
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LYT0002/0004-0006
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Output Capacitor C5
The primary function of capacitor C5 is to smooth the inductor
current. Select a low or ultra-low ESR series if electrolytic types
are used to ensure capacitor heating is minimized. Ceramic or
solid polymer types are also suitable but are typically higher
cost per unit capacitance.
Select the voltage rating to be the nearest above the LED string
voltage. Select the initial capacitance value based on the ripple
current parameter calculated in the design spreadsheet. The
capacitance value may be further increased to reduce the LED
ripple current dependent on the specification requirements of
the driver. For long life use 105 °C or above rated parts unless
the ambient temperature inside the lamp is less than 80 °C and
select a series with an appropriate lifetime rating. Note that
operating electrolytic capacitors below their rated temperature
specification will significantly extend their lifetime e.g., 105 °C
capacitor operated at 80 °C will increase lifetime by a factor of
2 to 3.
Sense Resistor R2
Sense resistor should be a 1% tolerance and either pulse rated
or overdesigned to avoid resistance drift with time. If using a
standard metal film type, overdesign power rating by 2-4 times.
The value of the resistor is provided in the design spreadsheet.
Feedback Capacitor C4
Capacitor C4 can be a low-cost general purpose capacitor. It
provides a “sample and hold” function, charging to the sensed
current value during the off-time of LYTSwitch-0. Its value
should be 10 mF to 22 mF; smaller values cause poorer regulation
and lower efficiency. This capacitor also bypasses the switching
current during the free-wheeling period, reducing the sense
resistor dissipation.
LYTSwitch-0 Layout Considerations
In the buck or buck-boost converter configuration, since the
SOURCE pins in LYTSwitch-0 are switching nodes, the copper
area connected to SOURCE should be minimized to minimize
EMI within the thermal constraints of the design.
In the boost and non-isolated flyback configuration, since the
SOURCE pins are tied to DC return, the copper area connected
to SOURCE can be maximized to improve heat sinking.
The loop formed between the LYTSwitch-0, inductor (L2),
free-wheeling diode (D1), and output capacitor (C5) should be
kept as small as possible. The BYPASS pin capacitor C3
(Figure 7a) should be located physically close to the SOURCE (S)
and BYPASS (BP) pins. To minimize direct coupling from
DC
OUTPUT
C1
RF1
RV1
L1
R1
VR1
PI-7033-052913
Optimize hatched copper areas ( ) for heat sinking.
AC
INPUT
C2
C5
L2
D1
C4
R3
R2
BR1
~
~
+
–
LYTSwitch-0
FB
BP
D
S
S
S
S
U1
+
C3
Figure 7a. Recommended Printed Circuit Layout for LYTSwitch-0 in a Buck Converter Configuration using P Package.
Rev. B 06/15
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LYT0002/0004-0006
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switching nodes, the LYTSwitch-0 should be placed away from
AC input lines. It may be advantageous to place capacitors C1
and C2 in-between LYTSwitch-0 and the AC input.
Quick Design Checklist
As with any power supply design, all LYTSwitch-0 designs
should be verified for proper functionality on the bench. The
following minimum tests are recommended:
1. Correct diode selection – UF400x series diodes are
recommended only for designs that operate in MDCM at an
ambient of 70 °C or below. For designs operating in
continuous conduction mode (CCM) and/or higher ambient,
then a diode with a reverse recovery time of 35 ns or better,
such as the BYV26C, is recommended.
2. Maximum drain current – Verify that the peak drain current is
below the data sheet peak drain specification under
worst-case conditions of highest line voltage, maximum
overload (just prior to auto-restart) and highest ambient
temperature.
3. Thermal check – At maximum output power, minimum input
voltage and maximum ambient temperature, verify that the
LYTSwitch-0 SOURCE pin temperature is 110 °C or below.
This figure ensures adequate margin due to variations in
RDS(ON) from part to part. A battery powered thermocouple
meter is recommended to make measurements when the
SOURCE pins are a switching node. Alternatively, the
ambient temperature may be raised to indicate margin to
thermal shutdown.
4. Check for any presence of reverse current in the DRIAN pin
during start-up with the output capacitance fully discharged.
Presence of reverse current is possible for CCM (high-power
inductance >3 mH) at certain conditions for limited input
capacitance (VOUT = VBULK_MIN every input half-line AC cycle).
Using a current probe, check if negative current is measured
either by increase input capacitance, reduce inductance or
place an ultrafast diode in series with the Drain node.
5. Follow the design procedure in AN-60 for the optimum line
regulation.
6. Power factor can be optimized by adjusting the conduction
time of the bridge rectifier. Refer to AN-60 for more details.
In a LYTSwitch-0 design using a buck or buck-boost converter
topology, the SOURCE pin is a switching node. Oscilloscope
measurements should therefore be made with probe grounded
to a DC voltage, such as primary return or DC input rail, and not
to the SOURCE pins. The power supply input must always be
supplied from an isolated source (e.g. via an isolation transformer).
DC
OUTPUT
RF1
RV1
L1
R1
BR1
C1
U1
D1
C2
C5 VR1
PI-7032-061313
Optimize hatched copper areas ( ) for heat sinking.
AC
INPUT
LYTSwitch-0
S
D
S
S
S
BP
FB
~
~
+
–
C4
R3
R2
L2
+
C3
Figure 7b. Recommended Printed Circuit Layout for LYTSwitch-0 in a Buck Converter Configuration using D Package to Bottom Side of the Board.
Rev. B 06/15
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LYT0002/0004-0006
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Absolute Maximum Ratings(1,5)
DRAIN Pin Voltage .............................................. -0.3 V to 700 V
Peak DRAIN Pin Current (LYT0002) .............. 200 mA (375 mA)(2)
Peak DRAIN Pin Current (LYT0004) .............. 400 mA (750 mA)(2)
Peak DRAIN Pin Current (LYT0005) ............ 800 mA (1500 mA)(2)
Peak DRAIN Pin Current (LYT0006) .......... 1400 mA (2600 mA)(2)
FEEDBACK Pin Voltage .......................................... -0.3 V to 9 V
FEEDBACK Pin Current ................................................. 100 mA
BYPASS Pin Voltage ............................................... -0.3 V to 9 V
Storage Temperature ...................................... -65 °C to 150 °C
Operating Junction Temperature(3) ................... -40 °C to 150 °C
Lead Temperature(4) .........................................................260 °C
Notes:
1. All voltages referenced to SOURCE, TA = 25 °C.
2. The higher peak DRAIN current is allowed if the DRAIN
to SOURCE voltage does not exceed 400 V.
3. Normally limited by internal circuitry.
4. 1/16 in. from case for 5 seconds.
5. Maximum ratings specified may be applied, one at a time,
without causing permanent damage to the product.
Exposure to Absolute Maximum Rating conditions for
extended periods of time may affect product reliability.
Thermal Resistance
Thermal Resistance: P Package:
(qJA) ................................ 70 °C/W(3); 60 °C/W(4)
(qJC)(1) .................................................11 °C/W
D Package:
(qJA) ..................... ......... 100 °C/W(3); 80 °C/W(4)
(qJC)(2) ..................................................30 °C/W
Notes:
1. Measured on pin 2 (SOURCE) close to plastic interface.
2. Measured on pin 8 (SOURCE) close to plastic interface.
3. Soldered to 0.36 sq. in. (232 mm2), 2 oz. (610 g/m2) copper clad.
4. Soldered to 1 sq. in. (645 mm2), 2 oz. (610 g/m2) copper clad.
Parameter Symbol
Conditions
SOURCE = 0 V; TJ = -40 to 125 °C
See Figure 8
(Unless Otherwise Specified)
Min Typ Max Units
Control Functions
Output
Frequency fOSC TJ = 25 °C
Average 62 66 70
kHz
Peak-Peak Jitter 4
Maximum Duty Cycle DCMAX S2 Open 66 69 72 %
FEEDBACK Pin Turnoff
Threshold Current IFB TJ = 25 °C 30 49 68 mA
FEEDBACK Pin Voltage
at Turnoff Threshold VFB 1.54 1.65 1.76 V
DRAIN Pin
Supply Current
IS1
VFB ≥2 V
(MOSFET Not Switching)
See Note A
130 220 mA
IS2
FEEDBACK Open
(MOSFET
Switching)
See Notes A, B
LYT0002 165 260
mA
LYT0004 173 280
LYT0005 190 310
LYT0006 226 330
Rev. B 06/15
10
LYT0002/0004-0006
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Parameter Symbol
Conditions
SOURCE = 0 V; TJ = -40 to 125 °C
See Figure 8
(Unless Otherwise Specified)
Min Typ Max Units
Control Functions (cont.)
BYPASS Pin
Charge Current
ICH1
VBP = 0 V
TJ = 25 °C
See Note C
LYT0002/0004 -5.5 -3.35 -1.8
mA
LYT0005-0006 -7.5 -4.6 -2.5
ICH2
VBP = 4 V
TJ = 25 °C
See Note C
LYT0002/0004 -3.8 -2.3 -1.0
LYT0005-0006 -4.5 -3.3 -1.5
BYPASS Pin
Voltage VBP 5.55 5.8 6.10 V
BYPASS Pin
Voltage Hysteresis VBPH 0.8 0.95 1.2 V
BYPASS Pin
Supply Current IBPSC See Note D 68 mA
Circuit Protection
Current Limit ILIMIT
(See Note E)
di/dt = 55 mA/ms
TJ = 25 °CLYT0002
126 136 146
mA
di/dt = 250 mA/ms
TJ = 25 °C145 165 185
di/dt = 65 mA/ms
TJ = 25 °CLYT0004
195 210 225
di/dt = 415 mA/ms
TJ = 25 °C222 265 282
di/dt = 75 mA/ms
TJ = 25 °CLYT0005
240 257 275
di/dt = 500 mA/ms
TJ = 25 °C271 310 345
di/dt = 95 mA/ms
TJ = 25 °CLYT0006
350 375 401
di/dt = 610 mA/ms
TJ = 25 °C396 450 504
Minimum On Time tON(MIN)
LYT0002/0004 280 360 475
nsLYT0005 360 460 610
LYT0006 400 500 675
Leading Edge
Blanking Time tLEB
TJ = 25 °C
See Note F 170 215 ns
Thermal Shutdown
Temperature TSD 135 142 150 °C
Thermal Shutdown
Hysteresis TSHD See Note G 75 °C
Rev. B 06/15
11
LYT0002/0004-0006
www.power.com
Parameter Symbol
Conditions
SOURCE = 0 V; TJ = -40 to 125 °C
See Figure 8
(Unless Otherwise Specified)
Min Typ Max Units
Output
ON-State
Resistance RDS(ON)
LYT0002
ID = 13 mA
TJ = 25 °C42 55.2
W
TJ = 100 °C67 88.4
LYT0004
ID = 25 mA
TJ = 25 °C21 27.6
TJ = 100 °C40 44.2
LYT0005
ID = 35 mA
TJ = 25 °C11 13.8
TJ = 100 °C19 22.1
LYT0006
ID = 45 mA
TJ = 25 °C6 8.1
TJ = 100 °C11 12.9
OFF-State Drain
Leakage Current IDSS
VBP = 6.2 V,
VFB ≥2 V,
VDS = 560 V,
TJ = 25 °C
LYT0002 50
mA
LYT0004 60
LYT0005 75
LYT0006 90
Breakdown Voltage BVDSS
VBP = 6.2 V, VFB ≥2 V,
TJ = 25 °C700 V
Rise Time tRMeasured in a Typical Buck
Converter Application
50 ns
Fall Time tF50 ns
DRAIN Supply Voltage 50 V
Output Enable Delay tEN See Figure 10 10 ms
Output Disable
Setup Time tDST 0.5 ms
Auto-Restart
ON-Time tAR
TJ = 25 °C
See Note H
LYT0002
ms
LYT0004-0006 50
Auto-Restart
Duty Cycle DCAR
LYT0002
%
LYT0004-0006 6
Not Applicable
Not Applicable
NOTES:
A. Total current consumption is the sum of IS1 and IDSS when FEEDBACK pin voltage is ≥2 V (MOSFET not switching) and the sum of
IS2 and IDSS when FEEDBACK pin is shorted to SOURCE (MOSFET switching).
B Since the output power MOSFET is switching, it is difficult to isolate the switching current from the supply current at the DRAIN.
An alternative is to measure the BYPASS pin current at 6 V.
C. See Typical Performance Characteristics section Figure 15 for BYPASS pin start-up charging waveform.
D. This current is only intended to supply an optional optocoupler connected between the BYPASS and FEEDBACK pins and not
any other external circuitry.
E. For current limit at other di/dt values, refer to Figure 14.
F. This parameter is guaranteed by design.
G. This parameter is derived from characterization.
H. Auto-restart on time has the same temperature characteristics as the oscillator (inversely proportional to frequency).
Rev. B 06/15
12
LYT0002/0004-0006
www.power.com
Figure 8. LYTSwitch-0 General Test Circuit.
PI-3490-060204
50 V50 V
DFB
SS
SS
BP
S1
470 kΩ
S2
0.1 µF
470 Ω
5 W
PI-3707-112503
FB
tP
tEN
DCMAX
tP = 1
fOSC
VDRAIN
(internal signal)
Figure 9. LYTSwitch-0 Duty Cycle Measurement. Figure 10. LYTSwitch-0 Output Enable Timing.
Rev. B 06/15
13
LYT0002/0004-0006
www.power.com
200
300
350
400
250
0
042 86 10 12 14 16 18 20
Drain Voltage (V)
Drain Current (mA)
PI-6813-061213
50
150
100
Scaling Factors:
LYT0002 0.5
LYT0004 1.0
LYT0005 2.0
LYT0006 3.4
25 °C
100 °C
Typical Performance Characteristics
Figure 15. BYPASS Pin Start-up Waveform.
1.1
1.0
0.9
-50 -25 0 25 50 75 100 125 150
Junction Temperature (
°
C)
Breakdown Voltage
(Normalized to 25 °C)
PI-2213-012301
6
5
4
3
2
1
0
00.2 0.4 0.6 0.8 1.0
Time (ms)
PI-2240-012301
BYPASS Pin Voltage (V)
7
Figure 11. Breakdown vs. Temperature.
Figure 13. Current Limit vs. Temperature at Normalized di/dt. Figure 14. Current Limit vs. di/dt.
Figure 16. Output Characteristics.
1.2
1.0
0.8
0.6
0.4
0.2
0
-50 -25 0 25 50 75 100 125
Junction Temperature (°C)
PI-2680-012301
Output Frequency
(Normalized to 25 °C)
Figure 12. Frequency vs. Temperature.
Normalized di/dt
PI-6812-061213
Normalized Current Limit
1.0
1.2
1.4
0.8
0.6
0.4
0.2
0
1 2 3 4 5 6
LYT0002
LYT0004
LYT0005
LYT0006
Normalized
di/dt = 1
55 mA/µs
65 mA/µs
75 mA/µs
95 mA/µs
Normalized
Current
Limit = 1
136 mA
210 mA
257 mA
450 mA
Temperature (°C)
PI-3709-111203
Current Limit
(Normalized to 25 °C)
1.0
1.2
1.4
0.8
0.6
0.4
0.2
0
-50 0 50 100 150
di/dt = 1
di/dt = 6
Normalized di/dt
Rev. B 06/15
14
LYT0002/0004-0006
www.power.com
Figure 17. COSS vs. Drain Voltage.
Typical Performance Characteristics (cont.)
Rev. B 06/15
15
LYT0002/0004-0006
www.power.com
Notes:
1. Package dimensions conform to JEDEC specification
MS-001-AB (Issue B 7/85) for standard dual-in-line (DIP)
package with .300 inch row spacing.
2. Controlling dimensions are inches. Millimeter sizes are
shown in parentheses.
3. Dimensions shown do not include mold flash or other
protrusions. Mold flash or protrusions shall not exceed
.006 (.15) on any side.
4. Pin locations start with Pin 1, and continue counter-clock-
wise to Pin 8 when viewed from the top. The notch and/or
dimple are aids in locating Pin 1. Pin 6 is omitted.
5. Minimum metal to metal spacing at the package body for
the omitted lead location is .137 inch (3.48 mm).
6. Lead width measured at package body.
7. Lead spacing measured with the leads constrained to be
perpendicular to plane T.
.008 (.20)
.015 (.38)
.300 (7.62) BSC
(NOTE 7)
.300 (7.62)
.390 (9.91)
.367 (9.32)
.387 (9.83)
.240 (6.10)
.260 (6.60)
.125 (3.18)
.145 (3.68)
.057 (1.45)
.068 (1.73)
.120 (3.05)
.140 (3.56)
.015 (.38)
MINIMUM
.048 (1.22)
.053 (1.35)
.100 (2.54) BSC
.014 (.36)
.022 (.56)
-E-
Pin 1
SEATING
PLANE
-D-
-T-
P08B
PDIP-8B (P Package)
PI-2551-040110
D S .004 (.10)
⊕
T E D S .010 (.25) M
⊕
(NOTE 6)
.137 (3.48)
MINIMUM
Rev. B 06/15
16
LYT0002/0004-0006
www.power.com
PI-4526-040110
D07C
3.90 (0.154) BSC
Notes:
1. JEDEC reference: MS-012.
2. Package outline exclusive of mold flash and metal burr.
3. Package outline inclusive of plating thickness.
4. Datums A and B to be determined at datum plane H.
5. Controlling dimensions are in millimeters. Inch dimensions
are shown in parenthesis. Angles in degrees.
0.20 (0.008) C
2X
14
5
8
26.00 (0.236) BSC
D
4
A
4.90 (0.193) BSC
2
0.10 (0.004) C
2X
D
0.10 (0.004) C2X
A-B
1.27 (0.050) BSC
7X 0.31 - 0.51 (0.012 - 0.020)
0.25 (0.010) MC A-B D
0.25 (0.010)
0.10 (0.004)
(0.049 - 0.065)
1.25 - 1.65
1.75 (0.069)
1.35 (0.053)
0.10 (0.004) C
7X
C
H
o
1.27 (0.050)
0.40 (0.016)
GAUGE
PLANE
0 - 8
1.04 (0.041) REF 0.25 (0.010)
BSC
SEATING
PLANE
0.25 (0.010)
0.17 (0.007)
DETAIL A
DETAIL A
C
SEATING PLANE
Pin 1 ID
B
4
+
++
4.90 (0.193)
1.27 (0.050) 0.60 (0.024)
2.00 (0.079)
Reference
Solder Pad
Dimensions
+
SO-8C (D Package)
Part Ordering Information
• LYTSwitch-0 Product Family
• LYT Series Number
• Package Identifier
PPlastic PDIP-8B
DPlastic SO-8C
• Tape & Reel and Other Options
Blank Standard Configurations
TL Tape & Reel, 2.5 k pcs minimum for D Package.
Not available for P Package.
LYT 0002 D - TL
Rev. B 06/15
17
LYT0002/0004-0006
www.power.com
Notes
For the latest updates, visit our website: www.power.com
Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability. Power
Integrations does not assume any liability arising from the use of any device or circuit described herein. POWER INTEGRATIONS MAKES
NO WARRANTY HEREIN AND SPECIFICALLY DISCLAIMS ALL WARRANTIES INCLUDING, WITHOUT LIMITATION, THE IMPLIED
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT OF THIRD PARTY RIGHTS.
Patent Information
The products and applications illustrated herein (including transformer construction and circuits external to the products) may be covered
by one or more U.S. and foreign patents, or potentially by pending U.S. and foreign patent applications assigned to Power Integrations.
A complete list of Power Integrations patents may be found at www.power.com. Power Integrations grants its customers a license under
certain patent rights as set forth at http://www.power.com/ip.htm.
Life Support Policy
POWER INTEGRATIONS PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR
SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF POWER INTEGRATIONS. As used herein:
1. A Life support device or system is one which, (i) is intended for surgical implant into the body, or (ii) supports or sustains life, and (iii)
whose failure to perform, when properly used in accordance with instructions for use, can be reasonably expected to result in significant
injury or death to the user.
2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause
the failure of the life support device or system, or to affect its safety or effectiveness.
The PI logo, TOPSwitch, TinySwitch, LinkSwitch, LYTSwitch, InnoSwitch, DPA-Switch, PeakSwitch, CAPZero, SENZero, LinkZero,
HiperPFS, HiperTFS, HiperLCS, Qspeed, EcoSmart, Clampless, E-Shield, Filterfuse, FluxLink, StakFET, PI Expert and PI FACTS are
trademarks of Power Integrations, Inc. Other trademarks are property of their respective companies. ©2015, Power Integrations, Inc.
Power Integrations Worldwide Sales Support Locations
World Headquarters
5245 Hellyer Avenue
San Jose, CA 95138, USA.
Main: +1-408-414-9200
Customer Service:
Phone: +1-408-414-9665
Fax: +1-408-414-9765
e-mail: usasales@power.com
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No. 218 Tianmu Road West,
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e-mail: chinasales@power.com
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District, Shenzhen, China,
518057
Phone: +86-755-8672-8689
Fax: +86-755-8672-8690
e-mail: chinasales@power.com
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Germany
Phone: +49-895-527-39110
Fax: +49-895-527-39200
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Italy
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Fax: +39-028-928-6009
e-mail: eurosales@power.com
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Yokohama-shi Kanagwan
222-0033 Japan
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RM 602, 6FL
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Phone: +65-6358-2160
Fax: +65-6358-2015
e-mail: singaporesales@power.com
Taiwan
5F, No. 318, Nei Hu Rd., Sec. 1
Nei Hu Dist.
Taipei 11493, Taiwan R.O.C.
Phone: +886-2-2659-4570
Fax: +886-2-2659-4550
e-mail: taiwansales@power.com
UK
First Floor, Unit 15, Meadway
Court, Rutherford Close,
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United Kingdom
Phone: +44 (0) 1252-730-141
Fax: +44 (0) 1252-727-689
e-mail: eurosales@power.com
Revision Notes Date
A Initial Release 06/13
B Updated with new Brand Style Logo. 06/15
Mouser Electronics
Authorized Distributor
Click to View Pricing, Inventory, Delivery & Lifecycle Information:
Power Integrations:
LYT0002D-TL LYT0002D LYT0002P LYT0005P LYT0005D LYT0006D LYT0004P LYT0006P LYT0004D
LYT0004D-TL LYT0005D-TL LYT0006D-TL