- 1 - E11711C22
Sony reserves the right to change products and specifications without prior notice. This information does not convey any license
by any implication or otherwise under any patents or other right. Application circuits shown, if any, are typical examples illustrating
the operation of the devices. Sony cannot assume responsibility for any problems arising out of the use of these circuits.
CXA3834AM
LED Backlight Driver IC
Description
The CXA3834AM is an LED driver IC with boost DC-DC converter. It enables luminance control using the peak
current and PWM signal, and blinking control using the BLINK signal. This IC has an optimum configuration for
realizing a simple and compact power supply circuit for an LCD TV equipped with a LED backlight.
(Applications: Power supply circuit, etc.)
Features
Shared
UVLO function
Overheat protection function
Error detection output function (xBL_ERR)
Detection timer latch function when abnormalities occur
LED driver control block
On-chip LED lighting FET gate driver
Luminance adjustment function using peak current control
Luminance adjustment function using the PWM signal
Blinking control using the BLINK signal
LED overcurrent detection function
DC-DC converter control block
On-chip boost type DC-DC converter
Output overvoltage detection function
Continuous overcurrent detection function
Slope compensation function
Structure
BiCMOS silicon monolithic IC
Package
16P-SOP
CXA3834AM
- 2 -
Absolute Maximum Ratings
*1 Allowable power dissipation reduction characteristics
Recommended Operating Conditions
Item Symbol Rating Unit Remarks
Maximum supply voltage VCC_MAX +24.0 V VCC
xBL_ERR pin voltage VxBL_ERR –0.3 to +24.0 V xBL_ERR
I/O pin voltage 1 VIO1 –0.3 to VCC + 0.3 V DRV, DIM_SW, PWM_DIM,
BLINK, DC_DIM, EN
VREF pin voltage VREF –0.3 to + 7.0 V VREF
I/O pin voltage 2 VIO2 –0.3 to VREF + 0.3 V ISENSE, OCP, COMP, FB,
PROTECT, OVP_DD
Allowable power dissipation PD*1 mW Allowable power dissipation
reduction characteristics
Operating ambient temperature Ta –30 to +85 C
Junction temperature Tj_max +150 C
Storage temperature range Tstg –55 to +150 C
1000
200
400
600
800
0–20 20 40 8060 100 120 140 160
Allowable power dissipation [mW]
Operating ambient temperature Ta [˚C]
72.1 ˚C20.7 ˚C 125 ˚C
193 mW
321 mW
When mounted on a 4-layer board
When mounted on a single layer board
Glass fabric base epoxy board 76 mm × 114 mm t = 1.6 mm
Item Symbol Rating Unit Remarks
Supply voltage range VCC 10.0 to 18.0 V
DC_DIM pin input voltage VDC_DIM 0.3 to 3.3 V
PWM_DIM pin input frequency FPWM_DIM
20 k to 40 k Hz Rated input frequency > 1 kHz
48 to 1 k Hz When PWM_DIM and BLINK
pin are short circuited.
PWM_DIM pin minimum pulse width TPWM_DIM 1.0 s
BLINK pin input frequency FBLINK
48 to 240 Hz
48 to 1 k Hz When PWM_DIM and BLINK
pin are short circuited.
BLINK pin input minimum pulse width TBLINK
2.0 ms
1.0 sWhen PWM_DIM and BLINK
pin are short circuited.
CXA3834AM
- 3 -
Pin Assignment
Block Diagram
16
12
14
11
13
10
15
2
1
3
5
6
7
8
9
4
R
SQ
Q
COMP
DC_DIM
PROTECT
xBL_ERR
PWM_DIM
BLINK
EN
VCC
VREF
DRV
ISENSE
OCP
DIM_SW
FB
GND
OVP_DD
Oscillator
clk
slope V/I
Slope Compensator
VREF 5.0 V
1.0 V
VREF
L/S
UVLO
Thermal
Shutdown
clk
slope
OCP
PWM
VREF
3.0 V
2.0 V/
1.0 V
Latch
23R
10R
Error Amplifier
2.0 V
Control Logic
latch ocp
dd_en
pwm_out
fb_ocp
dd_ovp
bl_err
pwm_in
blink_in
en
3.2 V
1.2 V
comp_ovp
CXA3834AM
- 4 -
Pin Assignment
Pin Table
Pin
No. Symbol Description Protective element
connection destination
1 DRV MOSFET driver output for boost converter —
2 ISENSE Current detection input for boost converter VREF, GND
3 OCP Overcurrent detection input for boost converter VREF, GND
4 EN Enable signal input VCC, GND
5 xBL_ERR Error signal output —
6 BLINK Blinking signal input VCC, GND
7 PWM_DIM PWM dimming signal input VCC, GND
8 DC_DIM Control voltage input VCC, GND
9 PROTECT Protection stop timer time adjustment VREF, GND
10 COMP Error amplifier output for boost converter control VREF, GND
11 VREF Reference voltage output VCC, GND
12 GND GND —
13 VCC Power supply input GND
14 FB LED current detection input VREF, GND
15 DIM_SW PWM dimming MOSFET driver output —
16 OVP_DD Boost converter output voltage detection input VREF, GND
DRV
ISENSE
OCP
1
2
3
4
6
8
5
7
14
13
12
11
9
10
EN
Top View
xBL_ERR
BLINK
PWM_DIM
DC_DIM
OVP_DD
DIM_SW
FB
VCC
GND
VREF
COMP
16
15
PROTECT
CXA3834AM
- 5 -
Pin Description
Pin
No. Symbol I/O Typical pin
voltage Equivalent circuit Description
1 DRV O VCC to GND
MOSFET driver output for
boost converter
(Connect to the boost
converter NMOS gate.)
2 ISENSE I/O 1.0 V to GND
Current detection input for
boost converter
(Connect to a slope
compensation resistor.)
3 OCP I 1.0 V to GND
Overcurrent detection input
for boost converter
(Connect to a current
detection resistor.)
4EN IV
CC to GND Enable signal input
5xBL_ERRI/OV
CC to GND
Error signal output
(Connect to a pull-up
resistor.)
1
DRV
V
CC
GND
Nch
Pch
Nch
Pch
2
ISENSE
GND
VREF
Pch
PchPch
3
OCP
GND
VREF
Pch
Pch
4
EN
GND
VCC
Pch
5
xBL_ERR
V
CC
GND
Nch
Nch
Pch
CXA3834AM
- 6 -
6 BLINK I 3.3 V to GND Blinking signal input
7 PWM_DIM I 3.3 V to GND PWM dimming signal input
8 DC_DIM I 3.3 V to GND
Control voltage input
(Connect to the R-C filter
output side.)
9 PROTECT I/O 3.0 V to GND
Protection stop timer time
adjustment
(Connect to the timer
adjusting capacitor.)
10 COMP I/O 3.8 V to GND
Error amplifier output for
boost converter control
(Connect the phase
compensation circuit between
COMP and GND.)
Pin
No. Symbol I/O Typical pin
voltage Equivalent circuit Description
6
BLINK
V
CC
GND
Pch
Nch
7
PWM_DIM
VCC
GND
Pch
Nch
8
DC_DIM
V
CC
GND
Pch
Pch
GND
VREF
Nch
Nch
9
PROTECT Pch
10
COMP
GND
VREF
Pch
Pch
Nch
CXA3834AM
- 7 -
11 VREF O 5.0 V
Internal supply voltage output
(Connect a stabilizing
capacitor.)
12 GND GND
13 VCC Power supply input
(Connect a stabilizing capacitor.)
14 FB I 1.0 V to GND
LED current detection input
(Connect to a current
detection resistor.)
15 DIM_SW O VCC to GND
MOSFET driver output for
PWM dimming
(Connect to the dimming
NMOS gate.)
16 OVP_DD I 3.2 V to GND
Output voltage detection input
for boost converter
(Connect to an output voltage
detection resistor.)
Pin
No. Symbol I/O Typical pin
voltage Equivalent circuit Description
11
VREF
GND
V
CC
Pch
Nch
Nch
GND
VREF
14
FB
Pch
Pch Pch
15
DIM_SW
GND
VCC
Pch
Nch
16
OVP_DD
GND
VREF
Pch
Pch
CXA3834AM
- 8 -
Electrical Characteristics
Shared Blocks
(
Unless otherwise specified, Ta = 25
C, V
CC
= 12 V, EN = 3.3 V, PWM_DIM = 3.3 V, BLINK = 3.3 V, DC_DIM = 3.3 V
)
Power Supply Block (VCC pin)
Reference Voltage Block (VREF pin)
Enable Signal Input Block (EN pin)
Error Output Block (xBL_ERR pin)
Protective Detection Pin (PROTECT pin)
Item Symbol Measurement conditions Min. Typ. Max. Unit
Operation start voltage VCC_ON 9.0 9.5 10.0 V
Operation stop voltage VCC_OFF 8.5 9.0 9.5 V
Hysteresis width VCC VCC_ON – VCC_OFF 0.3 0.5 0.7 V
Operating current consumption
ICC1 FB = 1.5 V
* Non switching —1.151.65mA
Current consumption
when stopped ICC2 EN = 0 V
PWM_DIM = 0 V —0.851.10mA
Item Symbol Measurement conditions Min. Typ. Max. Unit
Output voltage VREF 4.85 5.00 5.15 V
Input stability VREF_LINE VCC = 10.0 V to 18.0 V,
No load —1050mV
Load stability VREF_LOAD Iout = 0.1 m to 5.0 mA — 20 50 mV
Item Symbol Measurement conditions Min. Typ. Max. Unit
High level detection voltage VEN_H 1.9 2.0 2.1 V
Low level detection voltage VEN_L 0.9 1.0 1.1 V
Hysteresis width VEN VEN_H – VEN_L 0.9 1.0 1.1 V
Pin input resistance REN EN = 1.0 V 200 300 400 k
Item Symbol Measurement conditions Min. Typ. Max. Unit
Output Low voltage VxBL_ERR_L EN = 0 V, Iout = –3 mA — 0.15 0.3 V
Output off leak current IxBL_ERR_OFF xBL_ERR = 18 V — — 1.0 A
Item Symbol Measurement conditions Min. Typ. Max. Unit
Latch stop detection voltage VPROTECT 2.9 3.0 3.1 V
Charge current IPROTECT_CHG PROTECT = 1.0 V,
PWM_DIM = 12.0 V 8.0 10.0 12.0 A
Discharge current IPROTECT_RST PROTECT = 1.0 V 0.8 1.0 1.2 A
CXA3834AM
- 9 -
LED Driver Control Block
(
Unless otherwise specified, Ta = 25
C, V
CC
= 12 V, EN = 3.3 V, PWM_DIM = 3.3 V, BLINK = 3.3 V, DC_DIM = 3.3 V
)
MOSFET Driver Output Block (DIM_SW pin)
*1 Rise time and fall time use VCC 0.1 to VCC 0.9 as the judgment voltages.
Error Amplifier Input Circuit Block (FB pin, DC_DIM pin)
PWM Dimming Signal Input Block (PWM_DIM pin)
BLINK Signal Input Block (BLINK pin)
Item Symbol Measurement conditions Min. Typ. Max. Unit
Output rise time *1 TR_DIM_SW CLOAD = 1000 pF — 30 60 ns
Output fall time *1 TF_DIM_SW CLOAD = 1000 pF — 30 60 ns
Output High voltage VDIM_SW_H Iout = 10 mA 11.90 11.95 — V
Output Low voltage VDIM_SW_L PWM_DIM = 0 V,
Iout = –10 mA — 0.05 0.1 V
Item Symbol Measurement conditions Min. Typ. Max. Unit
Feedback control voltage 1 VFB_REF1 DC_DIM = 3.3 V 0.98 1.00 1.02 V
Feedback control voltage 2 VFB_REF2 DC_DIM = 1.65 V 0.495 0.500 0.505 V
FB pin pull-up current IFB FB = 0.1 V 0.05 0.1 0.2 A
Overcurrent detection voltage
VFB_OCP 1.9 2.0 2.1 V
DC_DIM pin input resistance RDC_DIM DC_DIM = 1.0 V 700 990 1300 k
Item Symbol Measurement conditions Min. Typ. Max. Unit
High level input voltage VPWM_DIM_H 2.0 — VCC –
2.0 V
Low level input voltage VPWM_DIM_L ——1.0V
Pin input resistance RPWM_DIM PWM_DIM = 1.0 V 200 300 400 k
Item Symbol Measurement conditions Min. Typ. Max. Unit
High level input voltage VBLINK_H 2.0 — VCC –
2.0 V
Low level input voltage VBLINK_L ——1.0V
Pin input resistance RBLINK BLINK = 1.0 V 200 300 400 k
CXA3834AM
- 10 -
DC-DC Converter Control Block
(
Unless otherwise specified, Ta = 25
C, V
CC
= 12 V, EN = 3.3 V, PWM_DIM = 3.3 V, BLINK = 3.3 V, DC_DIM = 3.3 V
)
MOSFET Driver Output Block (DRV pin)
*1 Rise time and fall time use VCC 0.1 to VCC 0.9 as the judgment voltages.
Error Amplifier Output Block (COMP pin)
Current Detection Circuit Block (ISENSE pin)
Overcurrent Detection Block (OCP pin)
Output Voltage Detection Block (OVP_DD pin)
Note) Shipping inspection is performed at room temperature. (The design is guaranteed with respect to
temperature fluctuation.)
Item Symbol Measurement conditions Min. Typ. Max. Unit
Output rise time *1 TR_DRV CLOAD = 1000 pF — 35 70 ns
Output fall time *1 TF_DRV CLOAD = 1000 pF — 25 50 ns
Output High voltage VDRV_H Iout = 10 mA (
Design guarantee
) 11.85 11.90 — V
Output Low voltage VDRV_L EN = 0 V, Iout = –10 mA — 0.03 0.1 V
Oscillation frequency FOSC ISENSE = 0 V,
OCP = 0 V, FB = 0 V 95 100 105 kHz
Maximum On duty DMAX ISENSE = 0 V,
OCP = 0 V, FB = 0 V 85 90 95 %
Item Symbol Measurement conditions Min. Typ. Max. Unit
Transconductance gm (Design guarantee) — 520 —
A/V
Output source current ICOMP_H FB = 0 V, COMP = 3.0 V 60 80 100 A
Output sink current ICOMP_L FB = 1.5 V, COMP = 0.5 V 60 80 100 A
Item Symbol Measurement conditions Min. Typ. Max. Unit
Slope compensation
output current ISLOPE
FB = 0 V, OPC = 0 V
(Peak current value during
maximum ON duty operation)
(Design guarantee)
—50—A
Item Symbol Measurement conditions Min. Typ. Max. Unit
Overcurrent limit
detection voltage VOCP FB = 0 V, ISENSE = 0 V 0.9 1.0 1.1 V
DD blanking pulse width TDD_BLK OCP = 1.5 V, FB = 0 V 350 500 650 ns
OCP pin pull-up current IOCP OCP = 0.1 V 0.05 0.1 0.2 A
Item Symbol Measurement conditions Min. Typ. Max. Unit
Output overvoltage
detection voltage VOVP 3.1 3.2 3.3 V
OVP_DD pin pull-up current
IOVP OVP_DD = 0.1 V 0.05 0.1 0.2 A
CXA3834AM
- 11 -
Detailed Description of Blocks
Start-up/Stop
CXA3834AM operation starts when voltage of 9.5 V (typ.) or more is applied to the VCC pin. When this voltage
is applied to the VCC pin, the internally generated reference voltage (VREF pin) is generated and the reset state
(POR) is canceled.
In addition, VCC has a built-in UVLO function, and when the VCC pin voltage falls to 9.0 V (typ.) or less, the IC
enters the reset state, the DC-DC converter stops operation and the DIM_SW output goes to Low output
regardless of the input signals of other pins.
When the VCC pin voltage rises to 9.5 V or more again, the reset is canceled and stopped functions can be
operated.
Fig. 1. Start-up and Stop Operation After Power-on
Enable (EN)
DC-DC converter and LED driver operations are enabled by setting the EN pin to 2.0 V or more.
In addition, the PWM_DIM pin and the BLINK pin must both be High for the DC-DC converter to start operation.
When the EN pin falls to 1.0 V or less, the DC-DC converter stops operating instantly, but the signal input to
the PWM_DIM pin is output on the DIM_SW pin. In addition, when the EN pin is Low, the signal input to the
PWM_DIM pin is output as is on the DIM_SW pin even when the BLINK pin is Low.
Fig. 2. Operation During Voltage Input to the EN Pin
RESET release RESETRESET
9.5 V
12 V
9.0 V
VCC
POR
(internal signal)
2.0 V
EN
PWM_DIM
BLINK
DIM_SW
1.0 V
DRV
(DC-DC converter operation)
CXA3834AM
- 12 -
Dimming Control Block
The CXA3834AM has an on-chip constant current mode boost DC-DC converter to generate the voltage
required to light the LED elements. The voltage (VOUT) boosted by the DC-DC converter is applied to the
anode side of the multiple LED elements connected in series, and when a High voltage is input to the
PWM_DIM pin, the DIM_SW pin also outputs a High voltage, the external FET is driven, and current flows to
the LED elements.
Fig. 3 shows a schematic of the operating circuit.
Fig. 3. CXA3834AM Operating Circuit Diagram
ISENSE
DRV
VOUT
FB
DIM_SW
VIN
Rfb
DC_DIM
23R
10R
ILED
OCP
PWM_DIM
BLINK
DC-DC
Controller
Control
Logic
CXA3834AM
CXA3834AM
- 13 -
LED Luminance Adjustment
The CXA3834AM can adjust the LED luminance using two different settings.
[Luminance Adjustment by PWM Control]
The pulse input to the PWM_DIM pin is output on the DIM_SW pin. The external FET gate is driven
and current flows to the LED elements in accordance with the DIM_SW pin output. The average current
flowing to the LED elements is proportional to the duty of the pulse input to the PWM_DIM pin, so the
LED element luminance can be adjusted by controlling the duty. (See Fig. 4.)
Use a CXA3834AM PWM_DIM pin input pulse with a frequency between 20 Hz and 40 kH (when
PWM_DIM and BLINK pin are short circuited, use them detween 48 Hz and 1 kHz), with a minimum
High pulse width of 1 s.
[Luminance Adjustment by Peak Current Control]
The current flowing to the LED elements is converted to a voltage by the FB resistor (Rfb), and this
voltage monitored by the FB pin of the CXA3834AM. The DC-DC converter compares the FB pin
voltage with the value 10/33 times the DC_DIM pin voltage (VDC_DIM), and controls the output voltage
(VOUT) to hold the same potential. That is to say, the current flowing to the LED elements or the FB
pin resistor can be controlled by controlling the DC_DIM pin voltage. The current flowing to the LED
elements is determined by the following formula.
Fig. 5 shows the relationship between the DC_DIM pin voltage and FB pin resistance value and the
current flowing to the LED elements.
The DC_DIM pin is pulled down internally by resistance of 990 k (typ.). When connecting a smoothing
RC filter to the DC_DIM pin, determine the constants in consideration of the IC internal impedance.
ILED VDC_DIM 10
33
------


Rfb [A]=
100
75
50
25
50 100
PWM_DIM duty [%]
DC_DIM = 3.3 V
Rfb = 10 Ω
Rfb = 5 Ω
PWM_DIM_Duty = 100 %
Rfb = 10 Ω
PWM_DIM_Duty = 100 %
1.65 3.3
DC_DIM input voltage [V]
LED average current [mA]
200
150
100
50
LED current [mA]
Fig. 4. PWM_DIM_Duty - I
LED
Characteristics Fig. 5. DC_DIM Voltage - I
LED
Characteristics
CXA3834AM
- 14 -
LED Blinking Control (Blinking)
The CXA3834AM has a BLINK pin, and the LED elements can be made to perform blinking operation by
switching the signal input to the BLINK pin between High and Low. When the BLINK signal is Low, the
DIM_SW pin is forcibly set to Low output (LED elements off), and at the same time the DC-DC converter
output voltage ripple is suppressed, so DC-DC converter boost operation (DRV output) is also forcibly
stopped. Fig. 6 shows operation relative to the signal input to the BLINK pin.
Fig. 6. Timing Chart During Blinking Operation
Use a CXA3834AM BLINK pin input pulse with a maximum frequency of 240 Hz with a minimum High pulse
width of 2 ms. (When PWM_DIM and BLINK pin are short circuited, use them with a maximum frequency
of 1 kHz with a minimum pulse width of 1 s.)
For applications that do not perform blinking operation, connect the BLINK pin to the VREF pin.
CXA3834AM
- 15 -
LED Overcurrent Detection Circuit Block
The CXA3834AM has an overcurrent detection function to detect abnormalities in the current flowing to the
LED elements. Fig. 7 shows the FB pin peripheral equivalent circuit.
Fig. 7. FB Pin Peripheral Equivalent Circuit
When a FB pin voltage of 2.0 V (typ.) or more is detected (LED_OCP), charging to the PROTECT pin starts
(charge current: 10 A (typ.)). LED_OCP is detected continuously, and when the PROTECT pin voltage
reaches 3 V, the IC is set to stop mode (latch stop). Charging to the PROTECT pin is performed only while
LED_OCP is detected. When LED_OCP is not detected, the PROTECT pin discharges at 1 A (typ.).
This IC generates a blanking pulse to prevent the above-mentioned overcurrent detection from malfunctioning.
This blanking pulse is approximately 500 ns (min.), and prevents false overcurrent detection due to the
inrush current that occurs when DIM_SW switches from Low to High. The FB pin voltage is controlled by
10/33 times the DC_DIM pin voltage, but note that overcurrent is detected more easily when the DC_DIM
pin voltage is set too high.
Fig. 8 shows the timing chart during LED_OCP operation.
Fig. 8. LED_OCP Detection Timing Chart
DRV
VOUT
FB
DIM_SW
Rfb
DC_DIM
23R
10R
ILED
DC-DC
Controller
PWM_DIM
PROTECT
2.0 V
Blanking
Pulse
Control
Logic
VREF
3.0 V
ERR_RST
ERR_SET
2.0 V
PWM_DIM
Blanking
Pulse
FB
ERR_SET
(OCP detection)
PROTECT
CXA3834AM
- 16 -
DC-DC Converter Control Block
Oscillator Circuit Block
The CXA3834AM DC-DC converter oscillating frequency is fixed to 100 kHz (typ.) by the internal circuit.
The maximum ON duty is 90 % (typ.), and the boost converter MOSFET ON time is normally proportional
to the COMP pin voltage. Fig. 9 shows the oscillator peripheral equivalent circuit.
Fig. 9. Oscillator Peripheral Equivalent Circuit
[Steady-state Operation]
When the CLK pulse is output from the oscillator, the DRV pin output goes High and current starts to flow
to the choke coil. The current that flows to the choke coil is converted to a voltage (Vocp) by the current
detection resistor (Rcs). The ISENSE pin voltage (Visense) is the sum of Vocp and the voltage generated
by the internal slope compensation current flowing to the slope compensation resistor (Rslope), and is
input to the PWM comparator non-inverted input pin. When Visense rises to the PWM comparator
inverted input pin (PWM_IN) voltage or more, the reset signal is generated and the DRV pin output goes
Low. The PWM_IN voltage (Vpwm_in) is the voltage obtained by level-shifting the COMP pin voltage
(Vcomp), and is determined approximately by the following calculation formula. Here, Vt corresponds to
the internal transistor threshold voltage, and is approximately 0.8 V in the CXA3834AM.
Vpwm_in = (Vcomp – Vt) 3/5
When the current flowing to the choke coil is low and Visense does not reach the PWM_IN voltage
during one cycle period, the DRV output automatically goes Low when the ON duty reaches 90 % (typ.).
The above operation is repeated and boost operation is continued until the prescribed current flows to
the LED elements.
Fig. 10 shows the DC-DC converter operation timing chart during steady-state operation.
Fig. 10. DC-DC Converter Operation Timing Chart
COMP
ISENSE
FB
DC_DIM DRV
VOUT
VIN
10R
23R
OCP
Oscillator
1.0 V
Error
Amplifier
PWM
Slope
Compensator
V/I
clk
slope
OCP
Rcs
Rslope
Rfb
VREF PWM
Comparator
Vocp
Visense
PWM_IN
L/S
SQ
QR
CLK
DRV
IL
PWM_IN
Vocp
+
Visense
CXA3834AM
- 17 -
[Overcurrent Detection]
The peak current flowing to the choke coil is constantly monitored by the OCP pin, and when the OCP
pin voltage reaches 1.0 V (typ.), the DRV pin output is forcibly set Low (pulse-by-pulse operation).
After overcurrent detection, the PROTECT pin is charged at 10 A (typ.) until the next cycle starts.
When overcurrent is detected continuously, the PROTECT pin is continuously charged, and when the
PROTECT pin voltage reaches 3 V, the IC latch stops.
The CXA3834AM generates a blanking pulse to prevent false OCP pin overcurrent detection.
This blanking pulse is 500 ns (typ.), and prevents false overcurrent detection due to the inrush current
that occurs when the DRV pin output switches from Low to High.
[Slope Compensation]
When the constant current mode boost converter is set so that the DRV pin ON duty is 50 % or more,
sub-harmonic oscillation may occur. The CXA3834AM can operate the boost converter stably even
when the ON duty is 50 % or more by inserting a series resistor (Rslope) to the ISENSE pin and
applying slope compensation. For details on sub-harmonic oscillation and slope compensation, see the
Application Notes.
CXA3834AM
- 18 -
COMP Pin Hold Circuit Block
The FB pin voltage temporarily goes to 0 V while a Low signal is input to the PWM_DIM pin and current is
not flowing to the LED elements (DIM_SW pin output signal Low period), so the COMP pin voltage and the
DC-DC converter output voltage rise temporarily. In this case, when a High signal is input to the PWM_DIM
pin in the next cycle, a transient current flows to the LED elements.
In the CXA3834AM, the COMP pin voltage immediately before a Low signal is input to the PWM_DIM pin
is held, and DC-DC converter operation continues. By holding the COMP pin voltage, operation can be
performed without a transient current flowing to the LED elements even when the PWM_DIM pin signal
goes High in the next cycle. Similar operation is also performed when the BLINK pin input signal is Low,
so that the COMP pin output voltage is held even when a Low signal is input to the BLINK pin and boost
operation stops.
Fig. 11 and Fig. 12 show the COMP pin hold function timing chart and the COMP pin peripheral equivalent
circuit, respectively.
Fig. 11. COMP Pin Hold Function Timing Chart
Fig. 12. COMP Pin Peripheral Equivalent Circuit
When the signal input to the PWM_DIM pin has a high frequency (up to approximately 40 kHz) and low duty,
the effect of the hold function reduces the COMP pin response speed, and may influence the start-up time
and the LED current characteristics. Make thorough evaluation before determining the phase
compensation constants Rcomp, Ccomp1 and Ccomp2 connected to the COMP pin. For details, see the
Application Notes. In addition, this IC detects the condition that FB pin voltage is fixed to Low when no
current flows to the LED elements due to error conditions such as DRV pin open. Therefore, this IC has a
function to output Low level of xBL_ERR signal when COMP voltage becomes 2.8 V (Min.) or more.
BLINK
PWM_DIM
COMP
VOUT
LED_Current
Hold
Hold
Hold Hold Hold Hold Hold Hold Hold
COMP
ISENSE
FB
DC_DIM
DRV
10R
23R SQ
QR
Error
Amplifier
L/S
HOLD_SW
ON/OFF
BLINK
PWM_DIM
Control
Logic
DIM_SW
Rcomp
Ccomp1
PWM
Ccomp2
CXA3834AM
- 19 -
Output Voltage Detection Circuit Block
Fig. 13 shows the OVP_DD pin peripheral equivalent circuit.
Fig. 13. OVP_DD Pin Peripheral Equivalent Circuit
The OVP_DD pin has a protective function that detects DC-DC converter output overvoltage. When an
OVP_DD pin voltage of 3.2 V (typ.) or more is detected (OVP), the IC instantly latch stops. To properly light
the LED elements during normal operation, set the breeder resistance ratio (Rovp1/Rovp2) so that the
voltage input to the OVP_DD pin is 3.2 V or less.
In addition, pull-up current of 0.1 A (typ.) is supplied from inside the IC in consideration of the case when
the OVP_DD pin is open. When the OVP_DD pin is open, the pin voltage is pulled-up to approximately the
VREF pin voltage, OVP is detected, and the IC latch stops. Therefore, set the Rovp2 resistance value to a
value that does not affect this 0.1 A current.
DRV
FB
Rfb
DC_DIM
23R
10R
ILED
DC-DC
Controller
VOUT
VIN
OVP_DD
3.2 V
Control
Logic
OVP
VREF
Rovp2
Rovp1
CXA3834AM
- 20 -
Protective Detection Functions
The CXA3834AM has various built-in protective functions to realize stable power supply operation.
When an error is detected by a protective function, the xBL_ERR pin outputs a Low signal, and either timer
latch operation is performed by charging the PROTECT pin or instant latch stop operation is performed.
Table 1 lists the protective functions, error conditions, and operation after detection. When the IC latch stops
after an error is detected, DC-DC converter operation stops and the DIM_SW pin outputs Low. When the IC
has performed latch operation (LATCH1), the latch can be canceled by turning the power supply off and then
on again, or by stopping and then restarting EN supply. When latch stop operation was performed due to
overheat protective detection (TSD) (LATCH2), the latch can be canceled only by turning the power supply off
and then on again.
Table 1. List of Protective Functions
[Backlight Error Detection Function]
When error number 1, 2, 6, 7, 8 or 9 in Table 1 is detected, the xBL_ERR pin outputs Low, and current is
pulled into the IC from an external voltage source via a pull-up resistor. When a backlight error is not detected,
the xBL_ERR pin is high impedance, so the external pull-up voltage source voltage is generated on the pin.
[Timer Latch Function]
When error number 3, 4, 5, 6, 7, 8 or 9 in Table 1 is detected, charging to the PROTECT pin starts, and
the IC latch stops when the PROTECT pin voltage reaches 3 V. The time after an error is detected until the
latch stop operation can be set by connecting a capacitor to the PROTECT pin. Fig. 14 and Fig. 15 show
the PROTECT pin peripheral equivalent circuit and the error detection timing chart, respectively.
[Instant Latch Function]
When error number 10 or 11 in Table 1 is detected, the IC instantly latch stops, and DC-DC converter and
dimming operation also stop. When the IC has latch stopped, the xBL_ERR pin outputs Low.
No. Protective function Detection conditions PROTECT pin
charging
xBL_ERR =
Low output
Backlight error detection function (xBL_ERR = Low output)
1 MOS_FET open detection
When the COMP pin output stays High
—
2 VREF overvoltage detection 1 VREF pin voltage > 6.0 V —
Timer latch function (PROTECT pin charging)
3DC-DC overcurrent detection
(DD_OCP) OCP pin voltage > 1.0 V —
4LED overcurrent detection
(LED_OCP) FB pin voltage > 2.0 V —
5 DRV pin error detection DRV pin input/output mismatch —
Backlight error detection and timer latch function
6PWM_DIM pin protective
detection
PWM_DIM pin voltage > V
CC
– 0.5 V
7 BLINK pin protective detection BLINK pin voltage > VCC – 0.5 V
8 DC_DIM pin protective detection DC_DIM pin voltage > VCC – 0.5 V
9 VREF overvoltage detection 2 VREF pin voltage > 5.5 V
Instant latch function 1 (Latch1)
10 DC-DC output overvoltage
protection (OVP) OVP_DD pin voltage > 3.2 V —
11 PROTECT latch stop detection PROTECT pin voltage > 3.0 V —
Instant latch function 2 (Latch2)
12 Overheat detection (TSD) Tj > 140 C—
CXA3834AM
- 21 -
Fig. 14. PROTECT Pin Equivalent Circuit
When an error is detected (ERR_SET = High), stable current of 10 A flows out from the IC via the
PROTECT pin. During normal operation (ERR_RST = High), stable current of 1 A flows into the IC via the
PROTECT pin.
Fig. 15. Error Detection Timing Chart
The timer time when an error is continuously detected can be expressed by the following formula.
PROTECT
VREF
3.0 V
ERR_SET
ERR_RST PROTECT
Logic
Internal
reference
voltage
1 µA
10 µA
Cp rst
ERR_SET
PROTECT pin
current
PROTECT
LATCH
PROTECT
Latch detected
dischg dischg dischg dischgchg chg chg
3.0 V
(internal_signal)
TCp (F3.0 V 10 A 0.3 Cp (s)==
CXA3834AM
- 22 -
[State Transition Diagram]
Fig. 16 shows the state transitions of this IC.
Fig. 16. State Transition Diagram
Note) RESET = High condition : VCC_UVLO = H or EN = L or VREF_UVLO = H or VREF_OVLO = H
LATCH1 = High condition : PROTECT = H or OVP = H
LATCH2 = High condition : TSD = H
RESET = Low condition : VCC_UVLO = L and EN = H and VREF_UVLO = L and VREF_OVLO = L
Initial state Error state 2
Error state 1Normal operating state
xBL_ERR = L xBL_ERR = L
xBL_ERR = LxBL_ERR = Hi-Z
VCC_UVLO = H
LATCH2 = H
LATCH1 = H
LATCH2 = H
LATCH2 = H
RESET = H
RESET = HRESET = L
CXA3834AM
- 23 -
Application Circuit
Fig. 17. Application Circuit (assuming Vin = 150 V, Vout = 300 V, ILED = 200 mA)
1V
VIN
200 µH
33 µF
2.2 kΩ
0.47 µF
4.7 kΩ
440 kΩ
660 kΩ
6.3 kΩ
5 Ω
CXA3834AM
1.0 µF
1.0 µF
0.1 Ω
PWM_DIM
BLINK
DC_DIM
12 V
12 V
BL_ON
10 kΩ
10 kΩ
4.7 kΩ
BL_ERR
161
2
3
4
5
6
7
8
12
9
10
11
13
14
15
PROTECT
DRV
OCP FB
DIM_SW
xBL_ERR
BLINK
PWM_DIM
DC_DIM
COMP
VREF
GND
VCC
ISENSE
OVP_DD
EN
VOUT
0.47 µF
2.2 kΩxx
Application circuits shown are typical examples illustrating the operation of the devices. Sony cannot assume responsibility for any problems
arising out of the use of these circuits or for any infringement of third party patent and other right due to same.
CXA3834AM
- 24 -
Example of Representative Characteristics
VREF pin output voltage VCC_UVLO operation start voltage
VCC_UVLO operation stop voltage
4.85
4.80
4.90
4.95
5.00
5.05
5.10
5.15
5.20
Current consumption when stopped
Operating current consumption
8.8
9.0
9.2
9.4
9.6
9.8
10.0
10.2
VREF pin output voltage [V]Current consumption when stopped [mA]Operating current consumption [µA]
VCC_UVLO operation start voltage [V]
9.6
9.4
9.2
9.0
8.8
8.6
8.4
VCC_UVLO operation stop voltage [V]
–30 0 30 60 90 120
Temp [˚C]
–30 0 30 60 90 120
Temp [˚C]
–30 0 30 60 90 120
Temp [˚C]
PROTECT pin latch detection voltage
3.15
3.10
3.05
3.00
2.95
2.90
2.85
Latch detection voltage [V]
–30 0 30 60 90 120
Temp [˚C]
1.2
1.1
1.0
0.9
0.8
0.7
0.6
2.0
1.5
1.0
0.5
0
–30 0 30 60 90 120
Temp [˚C]
–30 0 30 60 90 120
Temp [˚C]
CXA3834AM
- 25 -
FB pin control voltage 1
0.97
0.98
0.99
1.00
1.01
1.02
1.03
Control voltage 1 [V]
–30 0 30 60 90 120
Temp [˚C]
DRV pin oscillating frequency
94
92
96
98
100
102
104
106
108
Oscillating frequency [kHz]
–30 0 30 60 90 120
Temp [˚C]
DIM_SW pin rise time
0
10
20
30
40
50
60
70
Rise time [ns]
–30 0 30 60 90 120
Temp [˚C]
DIM_SW pin fall time
0
10
20
30
40
50
60
70
Fall time [ns]
–30 0 30 60 90 120
Temp [˚C]
FB pin control voltage 2
0.506
0.504
0.502
0.500
0.498
0.496
0.494
Control voltage 2 [V]
–30 0 30 60 90 120
Temp [˚C]
FB pin overcurrent detection voltage
1.85
1.90
1.95
2.00
2.05
2.10
2.15
Overcurrent detection voltage [V]
–30 0 30 60 90 120
Temp [˚C]
CXA3834AM
- 26 -
OVP_DD pin overvoltage detection voltage
3.35
3.30
3.25
3.20
3.15
3.10
3.05
Overvoltage detection voltage [V]
–30 0 30 60 90 120
Temp [˚C]
COMP pin source current
Source current [µA]
OCP pin overcurrent detection voltage
0.85
0.80
0.90
0.95
1.00
1.05
1.10
1.15
1.20
Overcurrent detection voltage [V]
–30 0 30 60 90 120
Temp [˚C]
COMP pin sink current
Sink current [µA]
DRV pin maximum ON duty
96
94
92
90
88
86
84
Maximum ON duty [%]
–30 0 30 60 90 120
Temp [˚C]
–30 0 30 60 90 120
Temp [˚C]
50
60
70
80
90
100
110
50
60
70
80
90
100
110
–30 0 30 60 90 120
Temp [˚C]
CXA3834AM
- 27 -
Package Outline
(Unit: mm)
MITSUI HT: 875340660
Marking
A3834M
CXA3834AM
- 28 - Sony Corporation
Package Outline
(Unit: mm)
SDT: 875339910
Marking
C
B
C:CXA3834AM
B: Lot No. (Max. 7)
▤ℂ⇟ภ(Control No.)
⵾ㅧㅳ(Week manufactured)
⵾ㅧᐕ(⷏ᥲᩴ)
(Year manufactured)