Datasheet

UBA2071_A_1 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 01 — 23 June 2008 18 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
If the fault timer is inactive, the CT pin voltage is 1 Vbe, about 0.7 V. The CT timer has a
protection that prevents the IC to start up if the CT pin is shorted to GND.
8.13 Communication
The UBA2071 and UBA2071A have a dedicated communication pin, the COMM pin, for
communicating with a slave half bridge driver (like the UBA2073), for instance for use in a
balanced half bridge driver configuration.
Via the COMM pin, a clock signal and a signal to indicate that both half bridge powers are
to be turned off are exported and a fault signal is imported. The clock signal is a digital
signal with a low level V
L(clk)(COMM)
and a high level V
H(clk)(COMM)
. To signal that both half
bridge powers should be turned off, the voltage at the COMM pin is raised to
V
O(hbswoff)(COMM)
.
The UBA2071 and UBA2071A look at the current drawn from the COMM pin during the
clock high period for a hard switching signal from the slave half bridge driver. First, a
non-overlap time period t
no
is discarded to prevent that a capacitive load on the
communication line is seen as a signal. Then the detected current is averaged over the
clock high period before being compared to the reference level I
th(det)hsw(COMM)
. The
current value is sampled on the falling edge of the clock signal and held during the clock
low period. The received signal is treated as equal to an internal hard switching detection
(so PWM dimming will be disabled, switching frequency will be increased and fault timer
will be started).
When only the UBA2071 or UBA2071A is used, the COMM pin must be “not connected”.
8.14 Protections
All fault conditions and how they are processed in the IC can be found in Figure 15.
The UBA2071 and UBA2071A have the following protections:
• OverVoltage Protection (OVP),
• OverVoltage Extra protection (OVE),
Fig 14. Fault timer waveforms
t
V
CT
0
t
V
NONFAULT
0
IC in
STOP-state
t
d(o)fault
014aaa110
t
to(fault)