ST L6520, L6521 User Manual
Highly integrated ballast controller for TL and CFL
Features
■ Half bridge circuit able to drive both BJT and
MOSFET transistors
■ Very accurate oscillator precision in wide
operating temperature range
■ BJTs' storage time compensation
■ Preheated start and instant start
■ Hard switching protection
■ Overcurrent / voltage protection
■ Choke saturation control
■ End-of-life protection
■ Programmable without capacitors
L6520
L6521
SO8
Applications
■ Electronic ballasts (TL, Industrial CFL)
■ Integrated CFLs
Table 1. Device summary
Order codes Package Packaging
L6520
Tube
Figure 1. Block diagram
3:0BGHW
9
9
(2/
)35(
9
9FF
X$
L6520TR Tape and reel
SO8
L6521 Tube
L6521TR Tape and reel
9&&
9FF
6WDUW8S 89/2
9
,1
9
$'&
9
,QWHUQDO9
/2*,&
9
9
5HJ
&25(
&&&%ORFN
9FF
7[0 7[/7[+
7KUHVKROG08;
+6'
/6'
+%&6
*1'
March 2011 Doc ID 16998 Rev 3 1/19
www.st.com
19
Contents L6520, L6521
Contents
1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5 Functions description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1 Start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.2 Preheating and instant start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.3 Ignition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.4 Run mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.5 Storage time compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.6 Current control circuit (CCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.6.1 Hard switching protection (HSP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.6.2 Overcurrent protection (OCPH) during ignition mode . . . . . . . . . . . . . . 11
5.6.3 Overcurrent protection (OCPL) during run mode . . . . . . . . . . . . . . . . . . 11
5.6.4 Choke saturation control (CSC) during ignition and run mode . . . . . . . 12
5.7 End of life (EOL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.8 Summary of protections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6 Typical electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7 Application examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
8 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2/19 Doc ID 16998 Rev 3
L6520, L6521 Description
1 Description
The L6520/1 is the first highly integrated ballast controller in the market able to drive both
BJTs and MOSFETs, providing all the necessary protections to ensure the maximum
reliability of the application in compliance with major safety and power consumption
regulations.
By adopting BJTs switches in the application, the IC allows to replace more expensive
MOSFETs, strongly reducing the system cost without compromises.
The IC represents also the best and cost effective solution to replace self oscillating
solutions when the key requirement is the reliability of the ballast. The benefits are an
increased MTBF and a reduction of the costs due to the return from the field.
The higher level of flexibility and integration provided allows the possibility to quickly design
ballast with any kind of lamp topology/size/power, without limitations. Depending on the
power of the lamp, the IC can work without PFC, with passive PFC or with active PFC. In the
latter case the L6562A from STMicroelectronics is the suggested IC for the most cost
effective solution.
The IC is fully programmable using only resistors and offers over current protections, choke
saturation control and hard switching protection thanks to a sophisticated current control
circuit (CCC). In ignition, the CCC limits both the maximum lamp voltage in case of old or
broken lamp, and also the lamp current in case of inductor saturation.
When the IC is driving bipolar transistors, a variable dead time ensures the correct base
discharge time avoiding cross conduction phenomena. Moreover, the IC prevents the failure
due to the lamp's end of life (EOL).
Doc ID 16998 Rev 3 3/19
Pin connection L6520, L6521
2 Pin connection
Figure 2. Pin connection
)35(
(2/
+%&6
3:0BGHW
9&&
+6'
/6'
*1'
Table 2. Pin description
Symbol Pin Description
FPRE 1 Preheating frequency programming and ignition modes selection
EOL 2 Window comparator input
HBCS 3 Current sensing input
PWM_det 4 Half bridge middle point monitor
GND 5 IC power and signal ground
LSD 6 Low side driver output
HSD 7 High side driver output
VCC 8 Power supply
4/19 Doc ID 16998 Rev 3
L6520, L6521 Maximum ratings
3 Maximum ratings
Table 3. Absolute maximum ratings
Symbol Pin Parameter Conditions Value Unit
Active clamp protection must not be supplied
by a low impedance voltage source
V
V
OD1
OD2
= VCC – V
= V
OUT –
OUT
GND
(1)
(1)
18.5 V
18.5 V
18.5 V
V
V
V
V
1. V
V
Z
I
VCC
V
OD1
V
OD2
V
FPRE
V
FPRE
PWM_det
PWM_det
V
HBCS
V
HBCS
EOL,max
EOL,min
OUT
8 Active clamp protection voltage
8 Active clamp protection current During low consumption state 2 mA
Differential voltage between
6,7
driver output and V
Differential voltage between
6,7
driver output and GND
CC
1 FPRE positive voltage 5 V
1 FPRE negative voltage -0.3 V
4 PWM_det pin positive voltage PWM_det input current < 5mA 5.1 V
4 PWM_det pin negative voltage PWM_det output current < 0.1mA -0.3 V
3 HBCS positive voltage 5 V
3 HBCS negative voltage HBCS output current < 2mA -5 V
2 EOL positive voltage EOL input current < 5mA 5 V
2 EOL negative voltage EOL output current < 0.1mA -0.3 V
refers to the voltage at either LVG pin or HVG pin
Table 4. Thermal data
Symbol Description Value Unit
thJA Max. thermal resistance junction to ambient 150 °C/W
R
T
J Junction operating temperature range -40 to 150 °C
STG Storage temperature -55 to 150 °C
T
Doc ID 16998 Rev 3 5/19
Electrical characteristics L6520, L6521
4 Electrical characteristics
(a)
VCC = 16 V, TA = -25 °C to 85 °C, unless otherwise specified
Table 5. Electrical characteristics
Symbol Pin Parameter Test condition Min. Typ. Max. Unit
Supply voltage
(2)
(1)
10.5 V
150 220 µA
Z
V
V
CC(ON)
V
CC(OFF)
V
CC
Z
VCC Operating range After turn-on
VCC Turn-on threshold 13.5 15 16.5 V
VCC Turn-off threshold 10.5 11.5 12.5 V
VCC Zener voltage IZ = 2 mA 16.5 17.5 18.5 V
Supply current
I
ST-UP
I
CC
I
Q
VCC Start-up current Before turn-on, (VCC = 13 V) 130 200 µA
VCC Operating supply current No load 8 10 mA
VCC Quiescent current IDLE mode,
Timing and oscillator
V
D Output duty cycle Run mode 49.5 50 50.5 %
t
DEAD
f
RUN
f
PRE
t
PRE
f
df
IGN
df
CCC
I
FPRE
t
ON,min
INS
Fixed dead time
HB run frequency
Max programmable
preheating frequency
Preheating time
HB instant start initial
frequency
/dt
/dt
Ignition time frequency sweep
rate
Frequency sweep rate after
overcurrent
FPRE FPRE current reference
HSD LSD Minimum half bridge on time T
(3)
T
= 25° C 46 46.6 47.2 kHz
AMB
1.24 1.42 1.6 µs
43.2 47.8 kHz
R
= 24.9 kΩ 96 100 104 kHz
FPRE
R
≥ 196 Ω,
FPRE
≥ 196 Ω,
R
FPRE
FPRE connected to GND,
(4)
, T
AMB
(4)
, T
AMB
T
= 25 °C 200 202 204
AMB
(1), (4)
, L6520 1.5 s
(2), (4)
, L6521 0.8
(2)
85 kHz
= 25 °C -2.75 kHz/ms
= 25 °C -500 Hz/ms
192 204
= 25 °C 1 µs
AMB
Half bridge drivers
V
HSD LSD Output low voltage Iload = 300 mA 3 V
OL
µA
a. This is a preliminary version: all the parameters are subject to change
6/19 Doc ID 16998 Rev 3
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