ST L6520, L6521 User Manual

L6520

L6521

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

SO8

Applications

■Electronic ballasts (TL, Industrial CFL)

■Integrated CFLs

Table 1.	Device summary
Order codes		Package	Packaging
L6520			Tube
L6520TR		SO8	Tape and reel
L6521			Tube
L6521TR			Tape and reel

Figure 1. Block diagram

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March 2011

Doc ID 16998 Rev 3

1/19

www.st.com

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(					9&&
		(2/					+6'
		+%&6					/6'
		3:0BGHW
							*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
VZ	8	Active clamp protection voltage	Active clamp protection must not be supplied						18.5		V
			by a low impedance voltage source
IVCC	8	Active clamp protection current	During low consumption state						2		mA
VOD1	6,7	Differential voltage between			(1)				18.5		V
		driver output and VCC	VOD1 = VCC – VOUT
V	6,7	Differential voltage between	V	= V	GND (1)				18.5		V
		driver output and GND
OD2			OD2	OUT –
VFPRE	1	FPRE positive voltage							5		V
VFPRE	1	FPRE negative voltage							-0.3		V
VPWM_det	4	PWM_det pin positive voltage	PWM_det input current < 5mA						5.1		V
VPWM_det	4	PWM_det pin negative voltage	PWM_det output current < 0.1mA						-0.3		V
VHBCS	3	HBCS positive voltage							5		V
VHBCS	3	HBCS negative voltage	HBCS output current < 2mA						-5		V
VEOL,max	2	EOL positive voltage	EOL input current < 5mA						5		V
VEOL,min	2	EOL negative voltage	EOL output current < 0.1mA						-0.3		V
1. VOUT refers to the voltage at either LVG pin or HVG pin
Table 4.	Thermal data
Symbol		Description							Value		Unit
RthJA	Max. thermal resistance junction to ambient							150			°C/W
TJ	Junction operating temperature range						-40 to 150				°C
TSTG	Storage temperature							-55 to 150			°C

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

V

CC

VCC

Operating range

After turn-on (1)

10.5

V

V

Z

VCC(ON)

VCC

Turn-on threshold

13.5

15

16.5

V

VCC(OFF)

VCC

Turn-off threshold

10.5

11.5

12.5

V

VZ

VCC

Zener voltage

IZ = 2 mA

16.5

17.5

18.5

V

Supply current

IST-UP

VCC

Start-up current

Before turn-on, (VCC = 13 V)

130

200

µA

ICC

VCC

Operating supply current

No load

8

10

mA

IQ

VCC

Quiescent current

IDLE mode, (2)

150

220

µA

Timing and oscillator

D

Output duty cycle

Run mode

49.5

50

50.5

%

tDEAD

Fixed dead time

(3)

1.24

1.42

1.6

µs

fRUN

HB run frequency

TAMB = 25° C

46

46.6

47.2

kHz

43.2

47.8

kHz

fPRE

Max programmable

RFPRE = 24.9 kΩ

96

100

104

kHz

preheating frequency

R

≥ 196 Ω, (1), (4), L6520

1.5

s

tPRE

Preheating time

FPRE

R

≥ 196 Ω, (2), (4), L6521

0.8

FPRE

f

HB instant start initial

FPRE connected to GND, (2)

85

kHz

frequency

INS

df

/dt

Ignition time frequency sweep

(4), T

= 25 °C

-2.75

kHz/ms

IGN

rate

AMB

df

/dt

Frequency sweep rate after

(4), T

= 25 °C

-500

Hz/ms

CCC

overcurrent

AMB

IFPRE

FPRE

FPRE current reference

TAMB = 25 °C

200

202

204

µA

192

204

tON,min

HSD LSD

Minimum half bridge on time

TAMB = 25 °C

1

µs

Half bridge drivers

VOL

HSD LSD

Output low voltage

Iload = 300 mA

3

V

a. This is a preliminary version: all the parameters are subject to change

6/19	Doc ID 16998 Rev 3