- 您现在的位置：买卖IC网 > Sheet目录342 > MC34848EPR2 (Freescale Semiconductor)IC LED DVR BACKLIGHT 8CH 48QFN
FUNCTIONAL DEVICE OPERATION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
FUNCTIONAL DEVICE OPERATION
BOOST
An integrated sense circuit is used to sense the voltage at
the LED current driver inputs and automatically sets the
output voltage to the minimum voltage needed to keep all
LEDs biased with the required current. Care has been taken
to ensure that the minimum required output voltage (also the
minimum VF of the LEDs) is used in order to minimize on-
chip power dissipation. The boost frequency is programmed
in the setup routine (see 'Configuration' below) from 200 kHz
to 1.2 MHz, or can be synchronized to an input signal if
provided at the SYNC_IN pin. If SYNC_IN is connected to
GND, an on-chip oscillator is used to generate the boost
frequency and the boost frequency is output on the
SYNC_OUT pin.
The boost converter also features Over-current Protection
(OCP). The OCP operates on a cycle by cycle basis.
However, if the OCP condition remains for more than 60 ms
then the boost regulator is latched off and GD asserts high to
shutoff the Q-FET. The device can only be restarted by
recycling the power supply.
The SLEW pin is used to limit the slew on the OUT_SW pin
to reduce noise and avoid EMI problems. If the slew rate is
reduced too much, the efficiency of the device will reduce.
The slew rate can be changed by tying a resistor from the
SLEW pin to GND.
The Boost converter has been designed to operate over a
wide range of switching frequencies. Table 9 shows the
recommended external components to ensure stable
operation under all operating conditions.
Table 9. Recommended External Components (V IN = 24 V ± 10%)
Switching Frequency [kHz]
200
300
400
500
600
700
900
1200
L [ μ H]
100
68
47
33
33
22
22
15
C O [ μ F]
150
100
68
47
47
33
33
22
R COMP [k ? ]
130
130
130
130
130
130
130
130
C COMP1 [nF]
1.5
1.0
0.7
0.6
0.5
0.4
0.3
0.2
C COMP2 [pF]
59
39
29
24
20
-
-
-
The output capacitor C O should be a low ESR type,
preferably a MLCC. If an electrolytic capacitor is used, a
small value ceramic capacitor should be connected in parallel
to C O to reduce the ESR, thus reducing the output ripple
voltage of the converter.
PWM DIMMING
Each channel has an independently programmable 10-bit
PWM generator. The data for the PWM generator is
programmed using the differential interface in standard
operating mode. If the channel is programmed with 0 duty
cycle, that channel is programmed off, and is ignored for
automatic output voltage control and for LED failure detection
(see Protection and Diagnostic Features ).
The PWM generator frequency can be programmed from
177 to 1200 Hz in 1.0 Hz step using a register in the start-up
control registers, and is generated by a PLL using RESET-
SCAN as the frequency reference. To operate in Master
mode, the SYNC_IN pin is connected to GND. The resulting
clock for PWM pulse generation is output on the SYNC_PWM
pin. A compensation network is connected between the
PLLC pin and GND. For Slave mode, the SYNC_PWM pin
acts as an input for the reference clock for the PWM
generator. In this manner, one device can be used as the
master IC, SYNC_IN tied to GND, (compensation network on
PLLC, and SYNC_PWM as output) and the remainder as
slaves (PLLC grounded, SYNC_PWM as input) just by
connecting the SYNC_PWM pins together.
The default Frame Frequency is 120 Hz. However, the
RESET-SCAN frequency input range can be between 80 and
180 Hz. Therefore, the resulting PWM frequency is given by
(F RESET-SCAN /120) x F PWM .
34848
Analog Integrated Circuit Device Data
22
Freescale Semiconductor
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
MC56F8006DEMO-T
BOARD DEMO FOR MC56F8006 DSP
MCB1114
BOARD EVALUATION FOR NXP LPC1114
MCB11C14
BOARD EVAL FOR NXP LPC11C14
MCB2470
BOARD EVAL NXP LPC247X SERIES
MCBSTM32EXL
BOARD EVALUATION FOR STM32F103ZE
MCBTMPM330
BOARD EVAL TOSHIBA TMPM330 SER
MCIMX25WPDKJ
KIT DEVELOPMENT WINCE IMX25
MCIMX53-START-R
KIT DEVELOPMENT I.MX53
相关代理商/技术参数
MC34849
制造商:SPC Multicomp 功能描述:HEADER VERTICAL 16WAY 制造商:SPC Multicomp 功能描述:WIRE-BOARD CONN, RECEPTACLE, 16POS, 3MM; Series:2261(5561); Pitch Spacing:3mm; Contact Termination:Through Hole Vertical; No. of Contacts:16; No. of Rows:2; Connector Mounting:PCB; Gender:Receptacle; Contact Material:Copper Alloy ;RoHS Compliant: Yes
MC34851
制造商:SPC Multicomp 功能描述:HEADER VERTICAL 18WAY 制造商:SPC Multicomp 功能描述:HEADER, VERTICAL, 18WAY
MC34853
制造商:SPC Multicomp 功能描述:HEADER R/ANGLE 16WAY 制造商:SPC Multicomp 功能描述:HEADER, R/ANGLE, 16WAY 制造商:SPC Multicomp 功能描述:WIRE-BOARD CONN, RECEPTACLE, 16POS, 3MM; Series:2261(5561); Pitch Spacing:3mm; Contact Termination:Through Hole Right Angle; No. of Contacts:16; No. of Rows:2; Connector Mounting:PCB; Gender:Receptacle; Contact Material:Copper Alloy ;RoHS Compliant: Yes
MC34855
制造商:SPC Multicomp 功能描述:HEADER R/ANGLE 18WAY 制造商:SPC Multicomp 功能描述:HEADER, R/ANGLE, 18WAY
MC34857
制造商:SPC Multicomp 功能描述:HEADER VERTICAL SMT 2WAY 制造商:SPC Multicomp 功能描述:HEADER, VERTICAL, SMT, 2WAY 制造商:SPC Multicomp 功能描述:WIRE-BOARD CONN, RECEPTACLE, 2POS, 3MM; Series:2261(5561)R; Pitch Spacing:3mm; Contact Termination:Surface Mount Vertical; No. of Contacts:2; No. of Rows:2; Connector Mounting:PCB; Gender:Receptacle; Contact Material:Copper Alloy ;RoHS Compliant: Yes
MC34859
制造商:SPC Multicomp 功能描述:HEADER VERTICAL SMT 4WAY 制造商:SPC Multicomp 功能描述:HEADER, VERTICAL, SMT, 4WAY 制造商:SPC Multicomp 功能描述:WIRE-BOARD CONN, RECEPTACLE, 4POS, 3MM; Series:2261(5561)R; Pitch Spacing:3mm; Contact Termination:Surface Mount Vertical; No. of Contacts:4; No. of Rows:2; Connector Mounting:PCB; Gender:Receptacle; Contact Material:Copper Alloy ;RoHS Compliant: Yes
MC3486
制造商:Panasonic Industrial Company 功能描述:I.C. (I)
MC34861
制造商:SPC Multicomp 功能描述:HEADER VERTICAL SMT 6WAY 制造商:SPC Multicomp 功能描述:HEADER, VERTICAL, SMT, 6WAY 制造商:SPC Multicomp 功能描述:WIRE-BOARD CONN, RECEPTACLE, 6POS, 3MM; Series:2261(5561)S; Pitch Spacing:3mm; Contact Termination:Surface Mount Vertical; No. of Contacts:6; No. of Rows:2; Connector Mounting:PCB; Gender:Receptacle; Contact Material:Copper Alloy ;RoHS Compliant: Yes