L6520TR STMicroelectronics, L6520TR Datasheet - Page 10

• Manufacturer Part Number: L6520TR
• Description: IC BALLAST CTRL TL/CFL 8-SOIC
• Manufacturer: STMicroelectronics
• Type: Ballast Controllerr

Specifications of L6520TR

• Current - Supply: 8mA
• Current - Output: 300mA
• Voltage - Supply: 10.5 V ~ 18.5 V
• Operating Temperature: -25°C ~ 85°C
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Frequency: -
• Lead Free Status / Rohs Status: Details
• Other names: 497-11128-2

Functions description
5.3
5.4
5.5
10/19
Ignition
During the ignition sequence the output frequency ramps down from the programmed
preheating frequency to the fixed run frequency with a fixed rate df
the instant start is selected, the frequency ramps down from 85 kHz to 46.6 kHz (typ.) with
the same rate.
The current control circuit limits the maximum lamp voltage (OCPH) in case of old or broken
lamp and it is able to control the lamp current in case of inductor saturation (CSC).
The ignition phase lasts for maximum 200 ms. If the Run frequency is not reached during
ignition phase, the IC is turned off (latched).
Run mode
The run frequency is internally set to 46.6 kHz.
The HSD and LSD pins drive respectively the high side and the low side switches. The
potential isolation to the high side switch is realized by a pulse transformer. The HSD and
LSD drivers are able to manage the inductive load represented by the primary side of the
pulse transformer.
Between the turn-off of one driver and turn-on of the other one there is a dead time
automatically optimized accordingly to the kind of the half bridge switches (MOS or BJT) to
ensure the maximum reliability. The CCC protects the circuit against over currents, choke
saturation and hard switching events.
Storage time compensation network
In all the operating states (preheating, ignition and run mode), the storage time
compensation ensures the application of the fixed dead time (t
BJT's collector current is effectively reduced to zero. The t
generated by internal logic and the propagation delay of PWM_det comparator.
The voltage level of the middle point of the half bridge is monitored through the PWM_det
pin: the high side switch is turned on after a fixed dead time from the instant when the
voltage on the PWM_det pin is above 2.65 V. The time between the falling edge of pin LSD
and the rising edge of HSD is recorded in order to set the same dead time between the
falling edge of pin HSD and the rising edge of pin LSD.
The minimum duration of the resulting ON time is internally limited to 1 µs. This condition
can last for a maximum time equal to 200 ms. After this time the IC is shut down (latched).
The PWM_det pin embeds a 5 V (typ.) clamping zener, allowing the connection between the
half bridge middle point and the pin itself by means of a limiting resistor.
When driving MOSFET no storage time is present, therefore the resulting dead time is equal
to (1.42 µs).
Doc ID 16998 Rev 3
DEAD
DEAD
is the sum of a fixed time,
IGN
, 1.42 us typ.) once the
/dt of - 2.75 kHz/ms. If
L6520, L6521