ZLED7012 Datasheet

© 2016 Integrated Device Technology, Inc.

10

April 20, 2016

2.6.

PCC Serial Digital Interface

The ZLED7012 detects the rising edges of the control signal input on the EN/SET pin via an internal counter and decodes the

signal into one of the 14 current level settings given in Table 2.1. The control signal timing can vary (even during a programming

cycle), and its frequency can range from high data rates (e.g., 1MHz) to very low rates (e.g., 15kHz). (Also see section 2.4.) After

sending the constant current level code data, the control system holds the EN/SET signal high for time TLAT

(500μs minimum) so

that the ZLED7012 latches the programmed current level code into the data register and the current level becomes active as

illustrated in Figure 2.1. The internal counter is then reset to zero to be ready for the next programming cycle. This process is

repeated for the next data sent by the control system for subsequent current level programming. See section 2.4 regarding the

low-current shutdown mode, which is entered when the EN/SET signal remains low for longer than TOFF (

500μs minimum).

Figure 2.1

PCC Serial Digital Interface Signal Timing

EN/SET

TLO

THI

TLAT

TOFF

Data Reg

1

2

n

n= 14

1

n

0

IOUT

3

Operating Conditions

3.1.

RF Noise Reduction

The ZLED7012 charge pump operates at a fixed frequency of 1MHz (typical) to limit noise and harmonics and prevent generation

of RF interference by the ZLED7012, which could affect operation of local communication devices, such as cell phones. The soft-

start feature also prevents noise transients caused by inrush currents due to charge pump start-up.

The ZLED7012 has significantly lower back-injected noise at the input pin of the charge pump (typically 60mV peak-to-peak),

compared to inductor-based DC/DC boost converter solutions for white LED backlight applications (typically 10 times higher).

3.2.

ZLED7012 Thermal Protection

The ZLED7012 includes an on-board temperature sensing circuit that shuts down the ZLED7012 and turns off its outputs if the die

junction temperature exceeds 160°C (typical).