LED7708 STMicroelectronics, LED7708 Datasheet - Page 28

• Manufacturer Part Number: LED7708
• Description: LED Lighting Drivers 16 Ch 85mA LED 3.6 to 36V 250kHz
• Manufacturer: STMicroelectronics

Specifications of LED7708

• Rohs: yes

Recommended operating conditions
28/53
The two current levels are set by connecting a resistor on both the ISETH and ISETL pins:
Equation 12
where K
Equation 13
where K
The lower level is generally used to keep the voltage across the LED string under control
during the off-phase of the dimming period; if a zero-current low level is required, the ISETL
pin must be connected to the device supply rail (LDO3).
The current generators of the LED7708 have been designed to be grouped (i.e. connected
in parallel) if required by the application. For stability reasons, the parallelization of the
current generators should be done when the programmed current is above 40 mA per
channel.
The current accuracy among different devices is guaranteed to be lower than ±2% through
the full output current range (20 mA-85 mA). Two current ranges are selectable in order to
optimize the overall current accuracy.
Table 10
Table 10.
Unused channels should be disabled through the CHSEL register and can be physically left
floating or shorted to ground.
Nominal LED current
H
L
provides some typical output currents for standard E96 values.
= 4.0 V.
I
= 1200 V.
CHX,ON
LED current vs. external resistor setting
85
75
60
50
40
30
20
15
[mA]
Doc ID 022698 Rev 1
I
I
CHX OFF
CHX ON
E96 series (1%)
R
,
,
ISETH
14.3
16.2
20.0
24.3
30.1
40.2
60.4
80.6
=
=
[kΩ]
-------------------
R
------------------
R
ISETH
K
ISETL
K
H
L
Actual LED current
I
CHX,ON
83.9
74.1
60.0
49.4
39.9
29.9
19.9
14.9
[mA]
LED7708