LD5805
06/15/2015
Step up, 4 strings, Max. 250mA/string, Multi-dimming mode
WLED Backlight Controller
REV. 01
General Description
Features
The LD5805 is a 4-channel linear current controller which

Input Voltage range: 6V to 36V
combines with a boost switching controller. It’s an ideal

Drives up to 4 strings in parallel, up to 250mA per
string
solution for driving high power LED backlights. The
LD5805 can achieve high accuracy of constant current to
4 LED strings with 4 internal MOSFET. For each LED

LED current balance rate is  2.7%

Programmable switching frequency

PWM Input for PDIM or ADIM dimming control
string, the current is adjustable to drive up to 250mA.
Use PDIM mode: PWM Input frequency Range
The LD5805 features 4 individual current regulator
100Hz ~ 1kHz
channels to give accurate driving current for each LED
Use ADIM mode: PWM Input frequency Range 1kHz
string. The current balance rate is  2.7%. The 10V gate
~ 30kHz
driver allows the use of standard level MOSFETs. It can
provide a PDIM or ADIM dimming control.

HV gate Voltage of 10V for driver

Multi-chip parallel operation

LED short and open protection
The LD5805 eliminates the audio noise by maintaining

LED pin short to ground protection
constant LED current regulation during ADIM dimming.

Programmable over-voltage protection
The other features include LED short and open protection,

Thermal shutdown
cycle by cycle current limit, and thermal shutdown.
Applications

Backlight for GPS, Portable DVD

LED Backlight for LCD Monitor/ TV
1
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
www.leadtrend.com.tw
LD5805
06/15/2015
Typical Application
VIN
R1
PWM
VIN
VCC
LPF
LDR
COMP
CS
PWM
EN
LED1
RT
LED2
OVP
GND
ISET
LED3
LED4
R2
EN
LD5805
Fig. 1: Application circuit for P-DIM 4 string LED light bar
VIN
R1
RLPF
CLPF
PWM
VIN
VCC
LPF
LDR
COMP
CS
PWM
EN
LED1
RT
LED2
OVP
GND
ISET
LED3
LED4
R2
EN
LD5805
Fig. 2: Application circuit for A-DIM 4 string LED light bar
2
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
www.leadtrend.com.tw
LD5805
06/15/2015
VIN
R1
COMP
PWM
VIN
VCC
LPF
LDR
COMP
CS
PWM
EN
LED1
RT
LED2
OVP
GND
ISET
LED3
LED4
R2
EN
LD5805
VIN
COMP
VIN
VCC
LPF
LDR
COMP
CS
PWM
EN
LED1
RT
LED2
OVP
GND
ISET
LED3
LED4
EN
LD5805
Fig. 3: Multi-chip parallel operation for 8 string LED light bar
3
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
www.leadtrend.com.tw
LD5805-DS-01 June 2015
1
2
3
4
5
6
7
8
LED4
ISET
OVP
RT
Leadtrend Technology Corporation
EN
CS
LDR
VCC
GND 3
14 LED2
2
3
ISET
OVP
15 COMP
14 LPF
VCC
9
EN
VIN
RT 8
9
LDR
10 CS
OVP 7
10 LPF
CS
11 LDR
8
7
6
5
EN
12 VCC
ISET 6
YYWWPP
11 COMP
LD5805GHE1
LED4 5
4
RT
13 VIN
1
LED4
16 PWM
TSSOP-EP-16
12 PWM
LED3 4
LED2 2
15 GND
13 LED1
LED1 1
DIP-16
16 LED3
9
VIN
10 LPF
11 COMP
12 PWM
13 LED1
14 LED2
15 GND
16 LED3
LD5805
06/15/2015
Pin Configuration
SOP-16
LD5805GS1
YYWWPP
YY:
WW:
PP:
LD5805GN1
YYWWPP
www.leadtrend.com.tw
4
Year Code
Week Code
Production Code
LD5805
06/15/2015
Ordering Information
Part number
Package
Top Mark
Shipping
LD5805GHE1
TSSOP-EP-16
LD5805GHE1
2500 /tape & reel
LD5805GS1
SOP-16
LD5805GS1
2500 /tape & reel
LD5805GN1
DIP-16
LD5805GN1
1800 /Tube/ Carton
The LD5805 is ROHS compliant/Green packaged.
Pin Descriptions
SOP/DIP
TSSOP
NAME
FUNCTION
1
5
LED4
LED String 4 Current Input.
2
6
ISET
LED current resistor setting
3
7
OVP
Output voltage and short detection pin.
4
8
RT
Operating frequency resistor setting
5
9
EN
Chip Enable pin, when pull-low is in shutdown mode.
6
10
CS
Power MOSFET Current Sense
7
11
LDR
8
12
VCC
9
13
VIN
10
14
LPF
11
15
COMP
Soft star Compensation circuit for Boost topology.
12
16
PWM
Input PWM Dimming Signal for brightness control
13
1
LED1
LED String 1 Current Input.
14
2
LED2
LED String 2 Current Input.
15
3
GND
Ground
16
4
LED3
LED String 3 Current.
Gate drive signal for external MOSFET.
Internal linear regulator output pin. Bypass with VCC to GND with a
ceramic capacitor of 1F or greater. VCC is for chip internal use only.
Input Power of the chip. Bypass with at least 1F ceramic capacitor
close to VIN pin.
Output dimming mode selection, This pin is connected with
capacitance for Analog dimming output.
5
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
www.leadtrend.com.tw
LD5805
06/15/2015
Block Diagram
RT
+0.55V
Current Limit
LDR
Logic
GDRV
Oscillator
LEB
CS
Q S
OVP
R
2.0V
GM
8
Protection
Logic
Vref
COMP
COMP
LED Short
OVP 2
2.6V
8.8V
4
LED Open
SCP
4
LED1
LED
Voltage
Detector
LED2
LED3
0.1V
4
0.1V
LED4
OVP
VIN
LDO
Reference
Internal
V/I reference
Internal
Power supply
EN
VCC
PWM
LPF
ILED= 1200/(RISET)
LPF
ISET
Vdc
6
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
www.leadtrend.com.tw
GND
LD5805
06/15/2015
Absolute Maximum Ratings
VIN, EN
40V
LED1 to LED4,
-0.3V ~ 85V
CS
-0.3V ~ 60V
LDR, VCC, LPF
-0.3V ~ 16V
PWM, COMP, RT, ISET, OVP
-0.3V ~ 5.5V
GND
+/-0.3V
ILED1 to ILED4
400mA
Package Thermal Resistance
SOP-16, JA
110 C/W
TSSOP-EP-16, JA
60 C/W
DIP-16, JA
80 C/W
Power Dissipation (Ta=85C, TJ=125C)
SOP-16
363mW
TSSOP-EP-16
666mW
DIP-16
500Mw
Maximum Junction Temperature
150C
Storage Temperature Range
-65C to 150C
Lead Temperature (Soldering, 10sec)
260C
ESD Voltage Protection, Human Body Model
2.5 KV
ESD Voltage Protection, Machine Model
250 V
Caution:
Stress exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stress above Recommended Operating Conditions may affect
device reliability.
Recommended Operating Conditions(1)
Item
Min.
Max.
Unit
-40
125
C
Input Supply Voltage
6
36
V
PWM, EN
0
5
V
60
250
mA
100
500
kHz
Operating Junction Temperature
ILED1 to ILED4
(2)
Switching Frequency
7
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
www.leadtrend.com.tw
LD5805
06/15/2015
Note:
1. The device is not guaranteed to function outside of its operating conditions.
2.
Its ILED1~ILED2 recommend range is defined by PWM is 100% dimming duty. If all the channels are in use, IC’s
thermal would be affected due to the voltage tolerance between the light bars and layout condition. It’s recommended
to choose a fit package to improve it. The maximum allowable power dissipation is a function of the maximum junction
temperature TJ (MAX), the junction-to-ambient thermal resistance θJA, and the ambient temperature TA. The maximum
allowable continuous power dissipation at any ambient temperature is calculated by P D (MAX) = (TJ (MAX)-TA)/θJA.
Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go
into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage.
8
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
www.leadtrend.com.tw
LD5805
06/15/2015
Electrical Characteristics
(VIN=12V, TA=25C, unless otherwise noted.)
PARAMETER
CONDITIONS
SYMBOL
MIN
TYP
MAX UNITS
Input Power
Input Voltage range
6
36
V
VIN Operating Current
EN=PWM=5V
IQVIN
6
15
mA
VIN Shutdown Current
EN=PWM=0V
IVI_OFF
10
15
uA
Turn ON Level
UVLO(ON)
VIN_ON
6.5
V
Turn OFF Level
UVLO(OFF)
VIN_OFF
4
UVLO_HYS
0.2
0.45
0.7
V
9
10
11
V
15
mA
Under Voltage Lockout
Hysteresis
V
LDO Regulator
LDO output voltage for VCC pin
VIN >12V
VVCC
VCC Output Current Capability
VIN >12V
IVCC
DRV Output Clamp Level
VIN >12V
VDRV_H
9
10
11
V
DRV Output Rise Time
CDRV=1nF, VIN ≥ 12V, *
Tr_DRV
25
45
65
ns
DRV Output Fall Time
CDRV=1nF, VIN ≥ 12V, *
Tf_DRV
10
30
50
ns
ILED
97
100
103
mA
±2.7
%
6
%
+/-5
%
Drive Logic
LED Current Regulation
Absolute tolerance of regulation LED
Current per Channel,
ILEDX (mA)= 1200 / RISET(k)
ISET=12Kohm
LEDs Current Matching
LED current= 100mA
Calculating (I(MAX)-I(MIN))/2xIAveragex100%
Absolute Tolerance of Regulation LED
Current per Channel at Minimum
Dimming
LEDs Current Matching
Calculating at Minimum Dimming
(I(MAX)-I(MIN))/2xIAveragex100%
LED regulation voltage
MATCH
ISET=12Kohm
ADIM=0V
ILEDA0_CAL
ISET=12Kohm
ADIM=0V
MATCH0
+/-3
ILED=100mA/per
channel
VLEDRG
0.45
2
V
Boost Controller
Switching frequency
100
Operating Frequency
RRT =148 k
Boost Maximum duty cycle
FSW=210kHz
Leading edge blanking time
LD5805-DS-01 June 2015
189
DMAX
85
TLEB
9
Leadtrend Technology Corporation
FSW200
www.leadtrend.com.tw
210
200
500
kHz
231
kHz
95
%
300
ns
LD5805
06/15/2015
PARAMETER
CONDITIONS
SYMBOL
MIN
Enable
VEN_H
2.2
Disable
VEN_L
Enable
VPWM_H
Disable
VPWM_L
TYP
MAX UNITS
EN and PWM Dimming
EN Logic
V
0.8
2.2
V
V
PWM Logic
EN Pull Down Resistance
0.8
V
*
REN
100
300
k
*
RLPF
35
65
k
LED Open String Protection Threshold OVP1
VOVP1
1.88
2
2.12
V
Shutdown Under Abnormal condition
VOVP2
2.36
2.6
2.84
V
LED Short Circuit Protection Threshold LED1~LED4
VLSCP
8.0
8.8
9.5
V
Boost Output Protection - Short circuit
VSCP
0.1
0.2
V
VSCPY
50
100
mV
LPF
LPF Output Resistance
Protection
OVP2
SCP
Boost Output Protection - Short circuit
Hysteresis
Thermal Shutdown threshold
*
150
C
Thermal Shutdown hysteresis
*
20
C
MOSFET Over-Current Protection
Current Sense Threshold
VOCP
Over load protection voltage
VOLP
*: Guaranteed by Design.
10
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
www.leadtrend.com.tw
0.45
0.55
1
0.65
V
V
LD5805
06/15/2015
Typical Performance Characteristics
Fig. 4
Fig. 6
System Startup, PWM Duty=100%
Fig. 5
Analog Dimming, FPWM=20kHz, Duty=50%
Fig. 7 LED Short Protection , PWM Duty=100%
Fig. 8 LED Open Protection , PWM Duty=100%
Fig. 9
11
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
PWM Dimming, FPWM=200Hz, Duty=50%
www.leadtrend.com.tw
Over Temperature Protection, PWM Duty=100%
LD5805
06/15/2015
Application Information
Switching Frequency Selection
Basic Description
LD5805 operate in fixed frequency mode. The constant
operation frequency is set by an external connected
The LD5805 is a high-efficiency driver, ideally for LED
resistor between RT pin and ground. The resistor value
backlight application. It incorporates with two major
blocks:
a
DC-DC
boost
controller
with
is follow as:
peak
current-mode control and a 4-channel LED driver with
Fsw (kHz) 
constant current of sink capability from 60mA to 250mA
per channel.
31050
RT (k)
Programming the LED Current
LD5805 features adaptive voltage control that adjusts
the converter output voltage according to the total
The LED current is programmable by placing a resistor
forward voltage of LED strings. It detects the drop of
between ISET pin and ground. Set the desired LED
LED voltage across the constant current-sink drivers
current according to the following equation:
and enhances power dissipation in the device.
I LED ( mA ) 
The other features include LED short and open
1200
RISET ( kΩ )
protection, cycle by cycle current limit, and thermal
shutdown.
Dimming Control
Current-Mode DC-DC Controller.
The LD5805 provides two dimming control is achieved
by applying an external PWM signal to the PWM pin.
The
peak
current-mode
controller
allows
boost
converter to generate the required output voltage for
Dimming control by dimming duty cycle and recommend
LED strings. The switching frequency is programmable
input frequency is:
in the range between 100 kHz and 500 kHz through a
When use PDIM mode, Input frequency Range on
resistor connected from RT pin to ground.
PWM pin is 100Hz to 1kHz. If use ADIM mode, Input
Once the device is turned on, the external MOSFET will
frequency Range on PWM pin is 1kHz to 30kHz.
drive the inductor current to ramp up linearly until the
PWM signal input for analog dimming, When a
MOSFET reaches the peak current level set by CS pin.
capacitor CLPF is connected between LPF pin and
The peak inductor current is sensed by measuring the
GND. IC provides analog dimming function while
voltage across the current-sense resistor RCS, which is
receiving an external PWM signal at PWM pin. The
connected from the source of external MOSFET to
capacitor performs the integration of the external PWM
ground. LD5805 features leading edge blanking time to
signal to a DC level for regulating the amplitude of the
suppress the switching noise from the external MOSFET.
LED current. Varying the PWM duty cycle form 100%
A DIM comparator compares the current-sense voltage
to 5% controls the amplitude of LED current from
and the slop compensation signal with the output of the
Maximum to Minimum of about 20:1 ratio. The LED
GM error amplifier. The device will turn off the external
current
MOSFET when the voltage over CS exceeds the error
according equation
amplitude
amplifier’s output voltage. This process repeats during
I LED (mA)  D 
every switching cycle to achieve peak current-mode
control.
12
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
www.leadtrend.com.tw
can
calculated
approximately
1200
RLPF (k)

RISET (k) RLPF (k)  50
LD5805
06/15/2015
Where: D is PWM duty cycle value. RLPF is optional
the LD5805 provides design flexibly by disabling the
resistor to keep LPF pin voltage low under IC disable
fourth channel, LED4 opened. It is required that a
condition.
resistor (RSET) connected between CS pin and Boost
MOS Source pin. The three LED strings should be
Short LED protection
connected to LED1-3 correspondingly.
The voltage of LED1 ~ LED4 pins exceeds a typical
threshold of approximately 8.8V during of normal
LED String Setting
RSET
1~3 Channel
4.7KΩ
1~4 Channel
100RΩ
operation, the corresponding string be turned off and
latched.
Suggest to check LED1~LED4 pins voltage is under
Multi-Chip Parallel Operation
90% of VLSCP value at input voltage is maximum and
LED string voltage is minimum condition. To avoid IC is
The LD5805 is flexible for extending LED Channels with
latched risk by short LED protection at enable moment.
two or three LD5805s in parallel. For the connection of
two LD5805s extending 8 strings LEDs (Max.2 ICs):
LED Open String Protection
(1) Connector the VIN pins of the master IC and the
When any one of the LED strings is open, the output
slave IC together to provide the power of the slave
voltage will boost up until the voltage of OVP reaches
IC internal logic circuitry.
the threshold of 2.0V approximately. The IC will ignore
the opened string and the others will remain operation. If
(2) Connector the COMP pins of the slave IC and the
all the strings are opened and the voltage at OVP
master IC together to regulate the voltage of all 8
reaches 2.0V, the MOSFET drive output will be turned
strings LEDs.
off and the IC will shut off and stay latched. Toggle ENA
(3) The MOS driving signals of the slave IC are not
to resume the operation.
used; the boost converter can be only driven by the
MOSFET Over-Current Protection
master IC.
(4) Do not let the CS pin of the slave IC floating,
The LD5805 provides cycle-by-cycle current limit to
connector it to GND.
protect the MOSFET. During the MOSFET turning on,
LD5805 detects the CS pin voltage and if inductor peak
(5) The EN and Dimming signals should be applied to
current to cause to VCS rises above approximately 0.55V,
both ICs.
the LDR will shut off.
It is recommended to use external PWM dimming mode
Output Terminal Short-circuit to ground
Protection
to achieve the accurate dimming synchronization of both
When output terminal is short circuit to ground then OVP
Loop compensation
parts.
voltage falls below about 0.1V, MOSFET driving output
The LD5805 has an internal trans-conductance error
(LDR pin) will turn off. This will protect the converter
amplifier for LED current regulation for COMP output to
from damage.
compensate the control loop. In case of open LED event
LED1-3 Channels Operation
that all LED strings are open, the COMP node will
For applications where only three LED strings are used,
compensate the control loop still. The external inductor,
output capacitor, the compensation resistor and the
13
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
www.leadtrend.com.tw
LD5805
06/15/2015
capacitor determine the loop stability. The inductor and
4. Use broader traces between power MOSFET drain,
output capacitor are chosen based on the performance,
inductor and diode. There is high current in these
size and cost. The compensation resistor and capacitor
traces. To minimize power loss in these traces, the
at COMP are selected to optimize control loop stability.
resistance of traces should be kept as low as
possible.
Thermal protection
5. Keep the LDR drive traces short and board between
Thermal protection limits total power dissipation in this
the IC driver output, LDR pin, and the power
device. When the junction temperature reaches 150C
MOSFET.
approximately, the thermal sensor signals the shutdown
logic turning off this device. The thermal sensor will turn
this device on again after the IC’s junction temperature
cools by 20C.
PCB Layout Guideline
It’s recommended to separate the high frequency
switching current from the low-level control signals in
layout. The high switching current (MOSFET, inductor,
LDR driver and LED return ends) may disturb the other
low-level signals in the feedback loop and protection
circuitry. As a result, it may cause the control function to
behave abnormally. To avoid these issues, a few
guidelines are recommended for the PCB layout, as
below.
1. VCC bypass capacitor connected with signal ground
must be placed as close as possible to the IC. The
traces between capacitor and VCC pin should be
kept as short as possible to avoid noise interference.
2. VIN bypass capacitor connected with signal ground
must be placed as close as possible to the IC. The
traces between capacitor and VIN pin should be kept
as short as possible to avoid noise interference.
3. Use broader traces for VIN, VOUT and power
ground. Components such as the power MOSFET
and decoupling capacitors connected to VIN, VOUT
and power ground, have high input/output current.
To minimize power loss in these traces, the
resistance of traces should be kept as low as
possible.
14
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
www.leadtrend.com.tw
LD5805
06/15/2015
Package Information
SOP-16
Dimension in Millimeter
Dimension in Inch
Symbol
Min
Max
Min
Max
A
9.800
10.010
0.386
0.394
B
3.800
4.000
0.150
0.157
C
1.346
1.753
0.053
0.069
D
0.330
0.510
0.013
0.020
F
1.27 TYP.
0.05 TYP.
H
0.178
0.254
0.007
0.010
I
0.100
0.254
0.004
0.010
J
5.790
6.200
0.228
0.244
M
0.380
1.270
0.015
0.050
θ
0°
8°
0°
8°
15
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
www.leadtrend.com.tw
LD5805
06/15/2015
TSSOP- 16-EP
Dimension in Millimeter
Dimension in Inch
Symbol
Min
Max
Min
Max
A
4.900
5.100
0.193
0.201
B
4.300
4.500
0.169
0.177
C
0.850
1.200
0.033
0.047
D
0.190
0.300
0.007
0.012
E
2.000
3.000
0.079
0.118
F
G
0.65 TYP.
2.000
H
0.026 TYP.
3.000
0.127 TYP.
0.118
0.005 TYP.
I
0.005
0.150
0.000
0.006
J
6.200
6.600
0.244
0.260
M
0.450
0.750
0.018
0.030
θ
0°
8°
0°
8°
16
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
0.079
www.leadtrend.com.tw
LD5805
06/15/2015
DIP-16 (300mil)
Dimension in Millimeter
Dimension in Inch
Symbol
Min
Max
Min
Max
A
18.880
19.320
0.743
0.761
B
6.096
7.112
0.240
0.280
C
---
5.334
---
0.210
D
0.356
0.584
0.014
0.023
E
1.140
1.780
0.045
0.070
F
2.337
2.743
0.092
0.108
I
2.921
3.556
0.115
0.140
J
7.366
8.260
0.290
0.325
L
0.380
---
0.015
---
Important Notice
Leadtrend Technology Corp. reserves the right to make changes or corrections to its products at any time without notice. Customers
should verify the datasheets are current and complete before placing order.
17
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
www.leadtrend.com.tw
LD5805
06/15/2015
Revision History
REV.
Date
Change Notice
00
12/17/2014
Original Specification.
01
06/15/2015
1. LED Short Circuit Protection Threshold Modify.
2. Absolute Tolerance of Regulation LED Current per Channel at Minimum Dimming
2%~6% @ ISET=12Kohm ADIM=0V.
3. LEDs Current Matching Calculating at Minimum Dimming +/-5% (Max.) @
ISET=12Kohm ADIM=0V.
4. Change order information
LD5805GHE1 for TSSOP-EP-16
LD5805GS1 for SOP-16
LD5805GN1 for DIP-16
18
Leadtrend Technology Corporation
LD5805-DS-01 June 2015
www.leadtrend.com.tw
Open as PDF
Similar pages