ST LED7708 User Manual

LED7708

16 channels x 85 mA LED driver with boost controller and 4-wire serial interface

Features

■Boost controller section

–3.6 V to 36 V input voltage range (LDO)

–Adaptive output voltage for high efficiency

–Internal +5 V LDO for gate driver supply

–Internal +3.3 V LDO for device supply

–High performance external MOSFET driver

–250 kHz to 1 MHz switching frequency

–Programmable OV and OC protection

–Fixed frequency peak current-mode control

–External synchronization for multi-device application

–Overtemperature alert and thermal shutdown

■LED array driver section

–16 channels with 85 mA/ch current capability

–±2% channel current accuracy

–±2% channel-to-channel current matching

–LED short-circuit and open channel fault detection and management

–4-wire, 30 MHz serial interface

–16 x16-bit, 1x256-bit or 1x192-bit serial data formats

–Grouped or independent channel PWM control

–Selectable 12/16-bit grayscale brightness control for local dimming

–Programmable internal dimming oscillator

–Programmable grayscale latency

–Master/slave chain configuration supported

Datasheet —production data

6&1&0. X X ,

PITCH

Description

The LED7708 has been specifically designed to supply several LEDs starting from a single lowvoltage rail. It integrates a boost controller, sixteen current generators and a 4-wire serial interface. The boost controller regulates the output voltage in an adaptive way, according to the LED requirements, resulting in an improved overall efficiency. All the current generators are 40 V-rated, allowing the LED7708 to drive several LEDs in series on each channel. The channels can be put in parallel for higher output current.

The brightness of the LEDs is controlled by using the serial interface. A selectable 12-bit or 16-bit grayscale brightness control allows independent PWM on each channel. A programmable on-chip dimming oscillator is provided for external circuitry simplification. The device has dedicated pins to lock to an external synchronization with other devices (master or slave) for noise reduction in multi-device applications. The LED7708 implements basic protection (OVP, OCP and thermal shutdown) as well as LED array protection. It can detect and manage open-LED and shorted-LED faults and different faultmanagement options are available in order to cover most application needs.

Applications

■TV and monitor backlight units for LCD panels

■Medium and large size LCD panel backlights

■RGB/RGGB backlight solutions

Table 1.	Device summary
Order codes		Package	Packing
LED7708		VFQFPN-48 7x7	Tube
			Tape and
LED7708TR		(exposed pad)
			reel

May 2012

Doc ID 022698 Rev 1

1/53

This is information on a product in full production.

www.st.com

Contents	LED7708

Contents

1	Typical application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		. 6
2	Pin function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		. 7
3	Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		10
4	Recommended operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . .		12
5	Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		13
6	Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		17
7	Device description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		18
	7.1	Device supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	18
8	Recommended operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . .		19
	8.1	Device power-up and soft-start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	20
	8.2	Device shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	21
	8.3	Boost controller section and output voltage control . . . . . . . . . . . . . . . . .	21

8.3.1 Output voltage optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 8.3.2 Boost converter loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 8.3.3 Slope compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 8.3.4 External MOSFET control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

8.4 Current generators section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 8.5 Serial interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

8.5.1 Serial interface architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 8.5.2 Serial interface internal registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 8.5.3 Internal registers access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 8.5.4 Brightness data formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 8.5.5 Brightness registers (BRTxx) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 8.5.6 DEVCFG0 register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 8.5.7 DEVCFG1 register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 8.5.8 GSLAT register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 8.5.9 CHSEL register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

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LED7708		Contents
8.5.10	CHSTA register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . . . 37
8.5.11	Internal registers initialization . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . . . 38

8.6 Dimming options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

8.6.1 Internal dimming oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 8.6.2 Dimming waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 8.6.3 Grayscale synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

8.7	Fault management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		43
	8.7.1	Overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	43
	8.7.2	Overtemperature alert and thermal protection . . . . . . . . . . . . . . . . . . . .	44
	8.7.3	Overcurrent protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	44
	8.7.4	LED short-circuit and open channel faults . . . . . . . . . . . . . . . . . . . . . . .	44

	8.8	Special function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		45
		8.8.1	Current generators gain adjust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	45
		8.8.2	Continuous status reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	46
9	Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			48
10	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			52

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List of tables	LED7708

List of tables

Table 1. Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Table 2. Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Table 3. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Table 4. Thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Table 5. Recommended operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Table 6. Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Table 7. Recommended operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Table 8. Output voltage states during regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Table 9. Handshake signals summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Table 10. LED current vs. external resistor setting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Table 11. Internal registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Table 12. Internal register operations encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Table 13. Brightness data formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Table 14. DEVCFG0 register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Table 15. DEVCFG1 register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Table 16. Available LED short detection thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Table 17. CHSEL register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Table 18. CHSTA register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Table 19. Default configuration of internal registers after POR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Table 20. FOSC pin setting options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Table 21. Function of pins involved in dimming control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Table 22. Dimming synchronization control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Table 23. Detected faulty conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Table 24. XFAULT pin behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Table 25. VFQFPN48 (7 x 7 x 1.0 mm.) package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Table 26. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

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LED7708	List of figures

List of figures

Figure 1. Basic application circuit schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Figure 2. Pin connection (through top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Figure 3. Simplified block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Figure 4. Soft-start waveforms (standalone operation) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Figure 5. Simplified output regulation circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Figure 6. Effect of slope compensation on small inductor current perturbation (D>0.5) . . . . . . . . . . 26 Figure 7. Simplified serial interface block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Figure 8. Timing diagram related to a DEVCFGx write operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Figure 9. 16-bit data format, write operation to the brightness register . . . . . . . . . . . . . . . . . . . . . . . 31 Figure 10. 256-bit data format, write operation to the brightness registers . . . . . . . . . . . . . . . . . . . . . 32 Figure 11. 192-bit data format, write operation to the brightness registers . . . . . . . . . . . . . . . . . . . . . 32 Figure 12. Dimming signals and synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Figure 13. Normal timing mode waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Figure 14. Inverted timing mode waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Figure 15. Dimming waveform and GSSY output pulse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Figure 16. Dimming waveform triggered by GSSY input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Figure 17. Internal signals connected to the XFLT pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Figure 18. Channels current gain adjust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Figure 19. Continuous reading mode disabled, 1x256-bit data format . . . . . . . . . . . . . . . . . . . . . . . . 46 Figure 20. Continuous reading mode enabled, 1x256-bit data format. . . . . . . . . . . . . . . . . . . . . . . . . 47 Figure 21. VFQFPN48 (7 x 7 x 1.0 mm.) package outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Figure 22. Recommended PCB footprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

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Typical application circuit	LED7708

1 Typical application circuit

Figure 1. Basic application circuit schematic

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LED7708	Pin function

2 Pin function

Figure 2. Pin connection (through top view)

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Table 2.		Pin description
		Pin	Function
			Serial interface (SI) core and digital I/O buffer supply input. Connect to LDO3 or to an
1		VSI	external supply (3 V-5 V). Insert a 100 nF bypass ceramic capacitor between this pin and
			SGND. Connect to the host controller’s supply when possible.
			Grayscale synchronization output or VSYNC input. When the internal dimming generation
2		GSSY	is set, a pulse at the end of each dimming cycle is provided for data stream
			synchronization. Also used as dimming synchronization input to lock the dimming cycles
			on the vertical sync pulses.
3		DIN	Serial interface data input.
4		DOUT	Serial interface data out.
5		DCLK	Serial interface data clock.
6		LE	Serial interface latch enable.
			Grayscale clock I/O. When the internal dimming oscillator is used, the grayscale clock is
7		GSCK	provided at this pin. The pin becomes the grayscale clock input if the internal dimming
			oscillator is disabled (see FOSC pin).
8		XFLT	Fault signal, open drain output. The pin goes low when a faulty condition occurs.
			Channel current OK handshake I/O. Used for extended output voltage regulation in multi-
9		IOK	device applications. Used by slave devices to request a higher output voltage to the
			master. A 100 k pull-up resistor to LD03 is required.
			Channel voltage OK I/O (inverted). Used for extended output voltage regulation in multi-
10		XVOK	device applications. Used by slave devices to request an output voltage reduction to the
			master. A 100 k pull-up resistor to LD03 is required.

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Pin function			LED7708
Table 2.		Pin description (continued)
		Pin	Function
			Internal DAC overflow I/O. Used for extended output voltage regulation and fault
11		XOVF	management in multi-device applications. It is used to inform slave devices that the
			maximum output voltage has been reached. A 100 k pull-up resistor to LD03 is required.
			Fault detection masking I/O. This signal is used for extended output voltage regulation &
12		XMSK	fault management in multi-device applications. It is used to avoid incorrect fault detection
			by forcing slave devices to ignore LED-short detection during output voltage steering. A
			100 k pull-up resistor to LD03 is required.
13		FSW	Switching frequency selection / synchronization input. Used to set the desired switching
			frequency of the boost controller. Also used as synchronization input.
14		SYNC	Boost converter synchronization output. The buffered switching clock signal is provided at
			this pin to eventually synchronize other SMPS in the host system.
			Dimming oscillator frequency. A resistor to ground sets the frequency of the internal
15		FOSC	grayscale clock dimming oscillator. If set high, the internal dimming oscillator is disabled
			and the GSCK pin becomes the clock input (see GSCK pin).
16		CLIM	Boost section current limit setting. A resistor between this pin and SGND sets the boost
			converter current limit.
17		SLOPE	Slope compensation setting. A resistor between this pin and SGND is required to set the
			proper amount of slope compensation to avoid sub-harmonic instability.
18		COMP	Transconductance amplifier output. Connect a simple RC series between this pin and
			SGND to properly compensate the loop-gain of the boost converter.
19		ISETH	Output current setting (on). Connect a resistor between this pin and SGND to set the
			current sunk by each channel during the on-phase of the dimming.
			Output current setting (off). Connect a resistor between this pin and SGND to set the
20		ISETL	current sunk by each channel during the off-phase of the dimming (LED biasing). Connect
			to LDO3 to disable the bias current.
21		SGND	Signal ground. Common return for signals and settings.
22		AGND	Analog Ground. Common return for the current generators (channels).
23		CH1	Driver output (channel) #1.
24		CH2	Driver output (channel) #2.
25		CH3	Driver output (channel) #3.
26		CH4	Driver output (channel) #4.
27		CH5	Driver output (channel) #5.
28		CH6	Driver output (channel) #6.
29		CH7	Driver output (channel) #7.
30		CH8	Driver output (channel) #8.
31		CH9	Driver output (channel) #9.
32		CH10	Driver output (channel) #10.
33		CH11	Driver output (channel) #11.
34		CH12	Driver output (channel) #12.
35		CH13	Driver output (channel) #13.

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LED7708			Pin function
Table 2.		Pin description (continued)
	Pin		Function
36		CH14	Driver output (channel) #14.
37		CH15	Driver output (channel) #15.
38		CH16	Driver output (channel) #16.
39		AGND	Analog ground. Common return for the current generators (channels).
			Minimum output voltage setting. Multi-level input (high, low, floating or resistor to SGND).
40		VMIN	Used in conjunction with the VFB pin to set the best output voltage range swing for a given
			LED array. See related section for further details.
41		CSNS	External MOSFET current sense input. Connect to the sensing resistor in series with the
			power switch (source of the power MOSFET node).
42		PGND	Power ground. Reference for the external MOSFET current sensing circuit and return for
			the gate driver.
43		GATE	External MOSFET gate driver output. Connected to the gate of the power MOSFET.
44		VDR	Gate driver supply. Internally connected to the 5 V LDO regulator. Bypass with a 1 µF
			ceramic capacitor to PGND as close as possible to the chip.
			3.3 V linear regulator enable. When high or floating, the internal 3.3 V linear regulator is
45		LREN	used to supply the device. Also used to turn off the device for power consumption
			reduction. To be left floating the internal 3.3 V LDO is overdriven by an external 3.3 V
			supply rail.
46		VIN	Input of the LDO linear regulators. Bypass with a 1µF ceramic capacitor to ground as close
			as possible to the chip.
47		LDO3	3.3 V device supply and internal 3.3 V linear regulator output. Bypass with a 1 µF ceramic
			capacitor to ground as close as possible to the chip.
48		VFB	Output voltage feedback for the boost controller. Connect to the central tap of the output
			resistor divider. See the related section for details.

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Absolute maximum ratings	LED7708

3 Absolute maximum ratings

Table 3.	Absolute maximum ratings
Symbol		Parameter	Pin	Min.	Max.	Unit
			VIN,	-	40
			CH1 to CH16
			LDO3	-	VIN+0.3
					3.6
			COMP, SYNC,
			ISETH, ISETL,		LDO3+0.3
			SLOPE, CLIM,	-
					3.6
			FOSC, VFB, XOVF,
			VMIN
			VSI	-	6
		Maximum pin voltage	DCLK, LE, DIN,		VSI+0.3	V
			GSCK, DCLK,	-
					6
			DOUT, GSSY
			IOK, XMASK, XVOK,	-	6
			XFLT, FSW, LREN,
			VDR	-	6
					VIN+0.3
			GATE	-	VDR+0.3
					6
			CSNS	-	LDO3+0.3
					3.6
		Continuous channel	CH1 to CH16	-	90	mA
		current
		Maximum current
		generator power	CH1 to CH16	-	0.5	W
		dissipation
			Human body model
ESD		ESD Rating	JEDEC JESD22-	-	2	kV
			A114

Table 4.		Thermal data
Symbol		Parameter	Conditions		Min.	Max.	Unit
			TA = 25	°C			W
P	D	Power dissipation(1)	T = 50	°C
			A
			TA = 85	°C
TJ,OP		Operating junction temperature			-40	150	°C

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LED7708				Absolute maximum ratings
	Table 4.	Thermal data (continued)
	Symbol	Parameter	Conditions	Min.	Max.	Unit
	TSTG	Storage temperature range		-50	150
	Rth,JA	Junction-ambient thermal			30	°C/W
		resistance

1. Device soldered to the STEVAL-ILL035V1 demonstration board.

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Recommended operating conditions	LED7708

4 Recommended operating conditions

Table 5.	Recommended operating conditions
Symbol	Parameter	Conditions	Min.	Max.	Unit
DC Characteristics
VVIN	VIN pin input voltage range		3.6	36
VLDO3	LDO pin input voltage range	VIN, LDO3 and VDR	3.0	3.6
		shorted together
VVDR	VDR pin input voltage range	VDR and VIN shorted	3.0	5.5	V
		together
VCHx	Channel voltage range			36
VVSI	Serial interface supply voltage		3.0	5.5
ICHx	Channel continuous current		20	85	mA
	Channel current when OFF		2	200	µA
	(adjustable)
AC Characteristics (VSI = 3.3 V)
fGSC	Grayscale clock frequency			25	MHz
fDCLK	Serial clock frequency			30
fSW	Boost converter switching frequency		200	1000	kHz
Tw,DCLK	DCLK pulse width		20
Tw,GSC	GSC pulse width		20
Tw,LE	LE pulse width		15
Tsu,DIN	DIN setup time		5		ns
Th,DIN	DIN hold time		5
Tsu,LE	LE setup time		5
Th,LE	LE hold time		5

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LED7708					Electrical characteristics
5	Electrical characteristics
	(VIN = 12 V; TAMB = 25 °C and VSI connected to LDO3 if not otherwise specified.)
Table 6.	Electrical characteristics
Symbol		Parameter	Conditions	Min.		Typ.		Max.		Unit
Supply section
		LREN turn-on threshold						1.4		V
		LREN turn-off threshold		1						µA
		LREN pull-up current				3
VUVLO,ON		LDO3 undervoltage lockout				2.9		3.0
		upper threshold
VUVLO,OFF		LDO3 undervoltage lockout		2.6		2.7				V
		lower threshold
VVSI,ON		VSI turn-on threshold				3.0		3.1
VVSI,OFF		VSI turn-off threshold		2.6		2.7
		3.3 V LDO output voltage	3.6 V ≤VVIN ≤28 V	3.2		3.3		3.4
			ILDO3=0 mA, DEN=0
VLDO3		3.3 V LDO load regulation	VVIN=3.6 V, DEN=0			30		100		mV
			0 mA ≤ILDO3 ≤40 mA
		3.3 V LDO drop-out voltage	ILDO3=40 mA, VLDO3=3.2 V	180		270
		5 V LDO output voltage	6 V ≤VVIN ≤28 V	4.5		5.0		5.5		V
			IVDR=0 mA, DEN=1
VVDR		5 V LDO load regulation	VVIN=6 V, DEN=1			60		200		mV
			0 mA ≤IVDR≤40 mA
		5 V LDO drop-out voltage	IVDR =40 mA, VVDR=4.5 V	150		200				mV
Boost controller
tON,min		Minimum switching on-time				100		170		ns
		Default switching frequency	FSW to LDO3	550		610		670
fSW										kHz
		Synchronization input		180				1020
		frequency
KFSW		Switching frequency	RFSW = 100 kΩ	4.4		5.0		5.6		Hz • Ω
		constant		10		x10	10	x10	10
				x10
IGATE,Pk		Gate driver current capability	CL=3.3 nF, sourcing			1.9				A
			CL=3.3 nF, sinking			2.1
tr,GATE		Gate driver rise time				9
		(10 to 90%)
			CL=3.3 nF							ns
tf,GATE		Gate driver fall time				10
		(90 to10%)

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Electrical characteristics							LED7708
Table 6.	Electrical characteristics (continued)
Symbol		Parameter	Conditions	Min.	Typ.	Max.		Unit
		FSW synchronization input				0.5
		low level
								V
		FSW synchronization input		2.2
		high level
		SYNC output duty cycle	FSW connected to LDO3	25	30	35		%
		SYNC output high level	ISYNC=1 mA	VLDO3
				-0.3 V				V
		SYNC output low level	ISYNC=-1 mA			0.4
		Adjustable power MOSFET	RCLIM=100 kΩ		100
		current sensing voltage						mV
			RCLIM=300 kΩ		300
Power consumption
		Shutdown current (SI off,
IVIN1		LED drivers off, SMPS off,	LREN low, VSI low			30
		LDOs off)						µA
		Shutdown current (SI active,	LREN floating VSI to LDO3
IVIN2		LED drivers off, SMPS off,			300	450
			DEN=0
		LDOs on)
			LREN floating; VSI, FOSC
		Quiescent current (LED	and ISETL to LDO3; DIN,
IVIN3		drivers off, boost section not	DCLK, LE, GSCK and GSSY		4
		switching)	to GND; VCHx=2 V;
			RISETH=60 kΩ
			LREN floating VSI and FOSC					mA
		Operating current (serial	to LDO3, DIN and DCLK
			toggling at 15 MHz, DOUT,
IVIN4		interface active, boost not			7
			GSSY and GSCK floating, LE
		switching)	to GND. VCHx=2 V,
			RISETH=60 kΩ
		Standby current (DIN, DCLK	VSI = 3.3 V		7
IVSI1		and LE to SGND, LED						µA
		drivers off, SMPS off, LREN	VSI = 5.0 V		9
		floating)
OV protection, output regulation
			VMIN tied to GND	1.275	1.30	1.325
VFB,OVP		Overvoltage protection	VMIN to LDO3	1.105	1.13	1.155		V
		reference threshold	RVMIN=220 kΩ	0.985	1.01	1.035
			VMIN floating	0.765	0.8	0.815
VFB,OVP		OVP hysteresis			6			mV

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LED7708					Electrical characteristics
Table 6.	Electrical characteristics (continued)
Symbol		Parameter	Conditions	Min.		Typ.	Max.	Unit
			VMIN to GND	1.136		1.161	1.186
		Maximum internal reference	VMIN to LDO3	0.967		0.992	1.017
		voltage for output regulation	RVMIN=220 kΩ	0.847		0.872	0.897
VDAC,FB			VMIN floating	0.630		0.655	0.680	V
			VMIN to GND	0.836		0.861	0.886
		Minimum internal reference	VMIN to LDO3	0.667		0.692	0.717
		voltage for output regulation	RVMIN=220 kΩ	0.547		0.572	0.597
			VMIN floating	0.330		0.355	0.380
Current generators
		Maximum output current	VCHx=0.6 V,
ICHxn		accuracy with respect to				±2%	±3%
			20 mA ≤ ICHx ≤85 mA
		(1)
		nominal value
		Maximum channel-to-	VCHx=0.6 V, RISETH=60 kΩ
ICHxy		channel output current				±2%
		(1)	(ICHx=20 mA)
		mismatch
		(all channels active)
VCHx		Minimum master channel	RISETH=60 kΩ, CRS=0			500	600
		feedback voltage	RISETH=15 kΩ, CRS=1			700	800	mV
VRW		Regulation window	RISETH=60 kΩ, RWAS=0	190		250	310
		amplitude	RISETH=60 kΩ, RWAS=1	400		500	600
ICHx,OFF1		Off-state channels current	VCHx=10 V, RISETL=50 kΩ	70		80	90	µA
ICHx,OFF2			VCHx=10 V, ISETL to LDO3			1	2
VTH,ISETL		ISETL input threshold		VLDO3-				V
		ICHx, OFF2		1
KISETH		Output current high-state	20 mA ≤ ICHx ≤85 mA	1164		1200	1236
		constant
KISETL		Output current low-state		3.5		4.0	4.5
		constant
Serial interface
		DIN, DCLK, LE, GSCK,
		GSSY low level input					1.32
		threshold	VSI=LDO3=3.3 V
		DIN, DCLK, LE, GSCK,
		GSSY high level input		1.6
		threshold						V
		DOUT and GSSY output low	VSI=LDO3=3.3 V				1.22
		level	ILOAD=-200 µA
		DOUT and GSSY output	VSI=LDO3=3.3 V	1.75
		high level	ILOAD=200 µA

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Electrical characteristics								LED7708
Table 6.	Electrical characteristics (continued)
Symbol		Parameter		Conditions	Min.	Typ.	Max.		Unit
Fault management
VCHx,FLT1				DTS0=1&	3.0	3.2	3.4
				DTS1=0
VCHx,FLT2		LED short-circuit detection		DTS0=0&	6.2	6.4	6.6		V
		threshold		DTS1=1
VCHx,FLT3				DTS0=1&	7.7	8.0	8.3
				DTS1=1
		XFLT output low level	IXFLT, SINK=4 mA			200	220		mV
Dimming oscillator
K		Internal dimming oscillator	R	=33.2 kΩ	3.86	4 x1011	4.14		Hz•Ω
		constant			x1011		x1011
OSC				FOSC
FGSCK,OSC		Internal dimming oscillator	RFOSC=100 kΩ			4			MHz
		frequency	RFOSC=16 kΩ			25
Thermal flag and protection
		Overtemperature alert				125			°C
		threshold
TOTA
		Overtemperature alert				20
		hysteresis
TOTP		Overtemperature protection				155
		threshold

1. Channel current accuracy is calculated as:

	(	ICHX – ITARGET			)	• 100
ICHX =	max------------------------------------------------
			ITARGET
		(	ICHX – ICHY	)	• 100
ICHY	= max--------------------------------------
			ITARGET

where X, Y=1..16, X≠Y.

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