SSL5021BTS
Compact low-ripple buck LED driver IC
Rev. 2 — 11 March 2015
Product data sheet
1. General description
The SSL5021BTS is a highly integrated, high-precision, non-isolated MOSFET/bipolar
buck controller. It is intended to drive LED lamps in universal mains non-dimmable lighting
applications up to 25 W. The SSL5021BTS is designed for low-ripple applications.
The SSL5021BTS operates in Boundary Conduction Mode (BCM) with on-time regulation.
Operating in BCM provides a constant output current control with high accuracy. Adaptive
switching frequency gives freedom to choose the inductor, which enables the optimization
of inductor size, efficiency and EMI.
The SSL5021BTS starts up and operates in switching mode directly from an external
resistor without dV/dt supply or auxiliary supply. This feature simplifies the V
CC
supply. It
allows a low-cost off-the-shelf inductor to be used, providing flexibility in application
design.
The SSL5021BTS comes in a compact TSOP6 package.
The SSL5031BTS is suitable for high power factor/Low-THD applications with a
high-temperature foldback function. The SSL5031CTS is best for high power
factor/low-THD applications without a high-temperature foldback function.
2. Features and benefits
Driving LED strings from a rectified mains supply, low-ripple (< ±5 %)
Small electronic Bill of Materials (BOM) enabling a compact solution and a small,
single layer Printed-Circuit Board (PCB) footprint
Excellent line and load regulation and LED output current accuracy
Efficient BCM operation with:
Minimal reverse recovery losses in freewheel diode
Zero Current Switching (ZCS) and valley switching for switch turn-on
Minimal inductance value and size required
High efficiency (up to 91 %)
Ultra low IC current during operation (< 150
A)
Auto-recovery protections:
UnderVoltage LockOut (UVLO)
Cycle-by-cycle OverCurrent Protection (OCP)
Internal OverTemperature Protection (OTP)
Output OverVoltage Protection (OVP)
Output Short Protection (OSP)
NXP Semiconductors
SSL5021BTS
Compact low-ripple buck LED driver IC
Thermal foldback protection via a single PTC or NTC resistor
Compatible with wall switches with built-in standby indicator lights (Hotaru switch)
Extended IC lifetime
3. Applications
The SSL5021BTS is intended for low-cost, non-isolated LED lighting applications with
accurate fixed current output up to 25 W for single mains or universal mains voltage
(90 V (AC) to 277 V (AC)).
4. Quick reference data
Table 1.
Symbol
V
CC
R
DSon
Quick reference data
Parameter
supply voltage
on-state resistance
Conditions
operating range
of internal switch
T
j
= 25
C
T
j
= 125
C
I
I(SW)
V
I(SW)
input current in pin SW triangle wave;
duty cycle < 20 %
input voltage on pin
SW
current limited at
8.8 mA;
internal switch off
-
-
2
0.4
0.75
1.20
-
-
0.90
-
+2
+22
A
V
[1]
Min
9.5
Typ
-
Max
16
Unit
V
[1]
An internal clamp sets the supply voltage. The current into the VCC pin must not exceed the maximum I
VCC
value (see
Table 4).
5. Ordering information
Table 2.
Ordering information
Package
Name
SSL5021BTS
TSOP6
Description
plastic surface-mounted package; 6 leads
Version
SOT457
Type number
SSL5021BTS
All information provided in this document is subject to legal disclaimers.
© NXP Semiconductors N.V. 2015. All rights reserved.
Product data sheet
Rev. 2 — 11 March 2015
2 of 20
NXP Semiconductors
SSL5021BTS
Compact low-ripple buck LED driver IC
6. Block diagram
Fig 1.
Block diagram
7. Pinning information
7.1 Pinning
Fig 2.
SSL5021BTS pin configuration (TSOP6)
SSL5021BTS
All information provided in this document is subject to legal disclaimers.
© NXP Semiconductors N.V. 2015. All rights reserved.
Product data sheet
Rev. 2 — 11 March 2015
3 of 20
NXP Semiconductors
SSL5021BTS
Compact low-ripple buck LED driver IC
7.2 Pin description
Table 3.
Symbol
ISNS
VCC
SW
DEMOVP
GND
COMP
Pin description
Pin
1
2
3
4
5
6
Description
current sense input
supply voltage
internal switch drain
input from LED output for demagnetization timing, valley detection,
temperature foldback, and OVP
ground
loop compensation to provide a stable response
8. Functional description
8.1 Converter operation
The SSL5021BTS is a power MOSFET and bipolar compatible controller. The converter in
the SSL5021BTS is a source/emitter switch, Boundary Conduction Mode (BCM), on-time
controlled system.
Figure 3
shows the basic application diagram for MOSFET.
Figure 4
shows the basic application diagram for bipolar.
The integrated switch is used to save IC supply current. It enables the use a single
external resistor as supply even in switching mode. This converter operates at the
boundary between Continuous Conduction Mode (CCM) and Discontinuous Conduction
Mode (DCM).
Figure 5
shows the waveforms.
When the internal switch is switched on at t0, the inductor current I
L
builds up from zero in
proportional with V
IN
- V
OUT
during the switch on-time (t0 to t1). Energy is stored in the
inductor.
When the internal switch switches off at t1, I
L
drops proportionally to the value of V
OUT
.
The current flows through the freewheeling diode and the output capacitor (t2 to t3). When
I
L
reaches zero, after a short delay (t3 to t00), a new switching cycle starts.
Fig 3.
SSL5021BTS basic application diagram for MOSFET
SSL5021BTS
All information provided in this document is subject to legal disclaimers.
© NXP Semiconductors N.V. 2015. All rights reserved.
Product data sheet
Rev. 2 — 11 March 2015
4 of 20
NXP Semiconductors
SSL5021BTS
Compact low-ripple buck LED driver IC
Fig 4.
SSL5021BTS basic application diagram for bipolar
8.2 On-time control
When measuring the inductor current I
L
using sense resistor R4, the on-time is regulated
so that the average regulated voltage on pin ISNS (V
intregd(AV)ISNS
) equals an internal
reference voltage. I
L
can be calculated with
Equation 1:
V
intregd
AV
ISNS
-
I
L
=
--------------------------------------
R4
+
0.09
Where:
(1)
•
0.09 = ISNS bond wire resistance.
•
is the buck topology duty cycle.
8.3 Valley detection
After I
L
has decreased to zero at t3, the LEDP voltage starts to oscillate around the bus
voltage (V
IN
) minus output voltage level (V
OUT
), with amplitude output voltage (V
OUT
) and
frequency (f
ring
). Valley detection is a special circuit that is integrated in the SSL5021BTS.
It senses when the LEDP voltage reaches its lowest level (valley) through DEMOVP pin
connection. If a valley is detected, the internal switch is switched on again. As a result, the
switch-on switching losses are reduced.
SSL5021BTS
All information provided in this document is subject to legal disclaimers.
© NXP Semiconductors N.V. 2015. All rights reserved.
Product data sheet
Rev. 2 — 11 March 2015
5 of 20
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