NPC SM8134AB

SM8134A
White LED Driver IC
OVERVIEW
The SM8134A is a charge pump type white LED driver. It can drive 1 to 4 backlight white LED connected in
parallel and 1 flash white LED, making the device ideal for camera-equipped cellular phones. The charge
pump switches between ×1 to ×1.5 boost mode in response to LED drive current requirements to extend battery life to the maximum. The boost switching occurs in response to the drive current of all the connected LED
and thus supports variations in LED forward-bias voltage drop (VF). Each LED drive current is controlled by a
5-channel LED drive current control circuit. The backlight LED drive current and ON/OFF control, and flash
LED drive current and ON/OFF control are all set by 3-wire serial interface data input. Also, an under voltage
lockout (UVLO) circuit is built-in to prevent incorrect operation when the battery voltage drops.
■
■
■
■
■
■
■
■
■
■
GND
DIN2
EN
SCK
PACKAGE DIMENSION
(Unit: mm)
TOP VIEW
3.0 ± 0.08
BOTTOM VIEW
1.8
B
A
1.8
■
■
3 = 1.5 ± 0.05
■
0.3 ± 0.1
■
SDA
DIN1
VOUT
VIN
0.5
■
DIN3
DIN4
DIN5
PGND
C1P
C1M
C2M
C2P
■
3.0 ± 0.08
■
(Top view)
C 0.3
0.2 S A B
S
0.22 ± 0.05
∆ 0.05 M S A B
0.2 S
0.05 S
0.5
0.7 ± 0.05
■
Noise reduction due to charge pump boost circuit
Automatic charge pump switching to conserve
power
Drives 1 to 4 backlight white LED
(30mA/ch at maximum setting)
Drives a flash white LED
(150mA at maximum setting)
Backlight and flash white LED brightness
adjustment
3-wire serial input interface for all setting and
control
Under voltage lockout (UVLO) circuit built-in
Soft start circuit built-in
Thermal protection circuit built-in
Input voltage range
• No-load current (IOUT = 0mA): 2.7 to 4.6V
• Load current (IOUT = 80mA): 3.0 to 4.6V
• Load current (IOUT = 180mA): 3.3 to 4.6V
• Load current (IOUT = 200mA): 3.4 to 4.6V
Quiescent current
• Not-switching (×1.0 mode): 0.3mA (typ)
• Switching (×1.5 mode): 1.7mA (typ)
Standby current: 0.01µA (typ)
Operating frequency: 750kHz (typ)
Maximum backlight LED current: 30mA/ch
Maximum flash LED current: 150mA
All LED total maximum current: 200mA
Backlight LED current matching (ILED = 20mA)
: ± 3%
Flash LED current accuracy (ILED = 150mA)
: ± 6.7%
Packages: 16-pin QFN
0.2 ± 0.05
■
PINOUT
0.1 ± 0.05
FEATURES
APPLICATIONS
■
■
■
■
Cellular phone
Digital still camera
PDA
Portable games
ORDERING INFORMATION
Device
Package
SM8134AB
16-pin QFN
SEIKO NPC CORPORATION —1
SM8134A
BLOCK DIAGRAM
VIN
C1M C1P
C2M C2P
Charge pump
1/ 1.5
VOUT
Thermal
shut down
Output voltage
control
DIN1
UVLO
DIN2
Current
control
&
Current
detect
SCK
DIN3
DIN4
Control
logic
SDA
DIN5
EN
GND
PGND
PIN DESCRIPTION
Number
Name
I/O
Description
1
C1P
–
Charge pump capacitor connection 1P
2
C1M
–
Charge pump capacitor connection 1M
3
C2M
–
Charge pump capacitor connection 2M
4
C2P
–
Charge pump capacitor connection 2P
5
VIN
–
Voltage supply
6
VOUT
O
LED drive voltage output
7
DIN1
O
LED drive current control output 1 (connect to ground when not used)
8
SDA
I
Serial data input
9
SCK
I
Serial data clock input
10
EN
I
Serial interface enable input
11
DIN2
O
LED drive current control output 2 (connect to ground when not used)
12
GND
–
Ground
13
DIN3
O
LED drive current control output 3 (connect to ground when not used)
14
DIN4
O
LED drive current control output 4 (connect to ground when not used)
15
DIN5
O
LED drive current control output 5 (connect to ground when not used)
16
PGND
–
Charge pump ground connection
SEIKO NPC CORPORATION —2
SM8134A
SPECIFICATIONS
Absolute Maximum Ratings
GND = PGND = 0V
Note. The device may suffer breakdown if any one of these parameter ratings is exceeded.
Parameter
Symbol
Rating
Unit
VIN
−0.3 to 5.5
V
VEN, VSCK, VSDA
–0.3 to VIN + 0.3
V
VDIN1 to 5
–0.3 to VIN + 0.3
V
VOUT
5.5
V
IOUT
500
mA
PD
800 (Ta = 25°C)*1
mW
TJMAX
+125
°C
Tstg
−55 to +125
°C
Supply voltage range
Input voltage range
Output voltage range
VOUT output current
Power dissipation
Junction temperature
Storage temperature range
*1. When mounted on a 4-layer PCB.
800
Power dissipation [mW]
800
640
600
480
400
320
200
0
25
35
45
55
65
75
85
Operating temperature [°C]
Recommended Operating Conditions
GND = PGND = 0V
Rating
Parameter
Supply voltage range
Input voltage range
Ambient temperature range
Pin
Symbol
Conditions
Unit
min
typ
max
VIN1
×1.0 mode, IOUT = 0mA
2.7
3.6
4.6
V
VIN2
×1.5 mode, IOUT = 80mA,
VF = 3.5V*1
3.0
3.6
4.6
V
VIN3
×1.5 mode, IOUT = 180mA,
VF = 3.5V*1
3.3
3.6
4.6
V
VIN4
×1.5 mode, IOUT = 200mA,
VF = 3.5V*1
3.4
3.6
4.6
V
EN, SCK,
SDA
VES
Each logic-level pin
0
−
VIN
V
−
Ta
−30
−
+85
°C
VIN
*1. The maximum value of VF in the drive LED
SEIKO NPC CORPORATION —3
SM8134A
Electrical Characteristics
DC Characteristics
GND = 0V, VIN = 3.6V, Ta = 25°C unless otherwise noted.
Rating
Parameter
Pin
Standby current
VIN
Quiescent current
VIN
Symbol
Condition
Unit
min
typ
max
ISTB
Standby mode
–
0.01
1.00
µA
IDD1
×1.0 mode, no load
–
0.3
1.0
mA
IDD2
×1.5 mode, no load
–
1.7
4.0
mA
Maximum output voltage
VOUT
VOUT
×1.5 mode VOUT maximum voltage
4.6
4.9
5.2
V
Maximum output current
VOUT
IOUT
×1.5 mode
200
–
–
mA
Operating frequency
C1M
fOSC
×1.5 mode switching frequency
650
750
850
kHz
Internal circuit power-ON
reset time*1
VIN
TPOR
Time from when power is applied until
internal circuit reset
–
0.05
1.0
ms
Soft start time
DIN1 to 5
TSS
Time between EN signal falling edge
and LED turning ON
–
1.0
3.0
ms
LED drive pin leakage current
DIN1 to 5
ILEAK1 to 5
Standby mode, VDIN1 to 5 = VIN
–
0.01
1.00
µA
LED drive current matching
DIN1 to 4
∆ ILED
×1.0 mode, matching between channels
with ILED1 to 4 = 20mA setting
–3.0
–
+3.0
%
LED drive current 1
DIN1 to 4
ILED1 to 4
×1.0 mode, ILED1 to 4 = 20mA setting
19.0
20.0
21.0
mA
LED drive pin voltage 1*2
DIN1 to 4
VDIN1 to 4
ILED1 to 4 = 20mA setting
–
160
–
mV
LED drive current 2
DIN5
ILED5
×1.5 mode, ILED5 maximum setting
140
150
160
mA
LED drive pin voltage 2*2
DIN5
VDIN5
IDIN5 maximum setting
–
400
–
mV
Under voltage lockout
threshold*3
–
VUV
VIN falling
1.6
1.9
2.2
V
Thermal protection circuit
operating temperature*1
–
TSD
–
170
–
°C
Thermal protection circuit
hysteresis*1
–
TSDHYS
–
20
–
°C
EN, SCK,
SDA
VIH
HIGH-level input voltage range
1.8
–
–
V
Logic-level input voltage
VIL
LOW-level input voltage range
–
–
0.6
V
EN, SCK,
SDA
IIL
EN = SCK = SDA = VIN
–
–
1.0
µA
IIH
EN = SCK = SDA = GND
–1.0
–
–
µA
Logic-level input current
*1. Design guaranteed value
*2. Pin voltage value which switching ×1.0 mode to ×1.5 mode when LED current shortage detection
*3. When UVLO is active, the output is stopped and internal register is reset.
SEIKO NPC CORPORATION —4
SM8134A
AC Characteristics
GND = 0V, VIN = 3.6V, Ta = 25°C unless otherwise noted.
Rating
Parameter
Symbol
Condition
Unit
min
typ
max
SCK clock cycle
tSCK
2000
–
DC
ns
SCK HIGH-level pulse width
tWH
800
–
–
ns
SCK LOW-level pulse width
tWL
800
–
–
ns
EN setup time
tCS
1000
–
–
ns
EN hold time
tCH
800
–
–
ns
EN recovery time
tCR
1000
–
–
ns
Write data setup time
tDS
600
–
–
ns
Write data hold time
tDH
600
–
–
ns
EN
tCS
tCR
tWL
SCK
tWH
tCH
tSCK
tDH
tDS
SDA
Data input timing diagram
SEIKO NPC CORPORATION —5
SM8134A
VOUT EFFICIENCY
VOUT power efficiency [%]
100
90
VF = 3.2V
80
VF = 3.4V
VF = 3.6V
VF=3.8V
70
60
50
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
4.4
4.6
VIN [V]
Efficiency of PIN vs. POUT
Backlight LED × 4pcs, ILED1 to 4 = 20mA,
Flash LED × 1pc, ILED5 = 0mA,
IOUT = 80mA
VOUT power efficiency [%]
100
90
VF = 3.2V
VF = 3.4V
80
VF = 3.6V
VF=3.8V
70
60
50
3.2
3.4
3.6
3.8
4.0
4.2
VIN [V]
Efficiency of PIN vs. POUT
Backlight LED × 3pcs, ILED1 to 4 = 16mA,
Flash LED × 1pc, ILED5 = 0mA,
IOUT = 48mA
SEIKO NPC CORPORATION —6
SM8134A
VOUT power efficiency [%]
100
90
80
VF = 3.2V
VF = 3.4V
VF = 3.6V
70
VF=3.8V
60
50
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
VIN [V]
Efficiency of PIN vs. POUT
Backlight LED × 4pcs, ILED1 to 4 = 20mA,
Flash LED × 1pc, ILED5 = 120mA,
IOUT = 200mA
VOUT power efficiency [%]
100
90
80
VF = 3.2V
VF = 3.4V
VF = 3.6V
70
VF=3.8V
60
50
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
VIN [V]
Efficiency of PIN vs. POUT
Backlight LED × 3pcs, ILED1 to 4 = 16mA,
Flash LED × 1pc, ILED5 = 150mA,
IOUT = 198mA
SEIKO NPC CORPORATION —7
SM8134A
FUNCTIONAL DESCRIPTION
Serial Interface
The SM8134A uses a 3-wire serial interface to control each setting. Input data on SDA is input MSB first in an
8 clock pulse cycle structure, with the first 4 cycles of data setting the mode and the next 4 the corresponding
mode data. Data bits on SDA are read as received data on the rising edges of the SCK clock after EN goes
HIGH. Only the leading 8 bits on SDA are read after EN goes HIGH and all subsequent input data bits are
ignored, but the received data is reflected in SM8134A operation with timing almost simultaneous with the EN
falling edge. Conversely, if less than 8 bits are input on SDA, the data is ignored to prevent incorrect operation.
All registers are write-only, and their status cannot be read. After power is applied, an internal power-ON reset
circuit initializes all registers to logic level LOW in standby mode. However, the possibility exists that there
may be insufficient reset time, depending on the VIN input voltage rise time and fall time, so reset mode (0H or
EH) should be expressly invoked after power is applied. There is no restriction in the input sequence when setting parameters. However, since the parameters are set in the same order as the data input sequence and the
time taken from LED ON/OFF data input to LED dimming data input can exceed the soft start time, it is highly
advisable to enter the LED dimming data first. The charge pump circuit, that supplies the LED drive voltage,
starts whenever any parameter in address 5H (LED ON register) is set to 1, with the LED drive voltage output
on VOUT. Conversely, when all parameters in address 5H are set to 0, all other parameter data settings input
after reset are retained in standby mode. The serial interface pins EN, SDA, and CSK are CMOS inputs, thus
the input voltage on VIN must be a logic-level voltage and should not be left open circuit (floating).
Control Data
Mode selection data
Setting data
M1
M2
M3
M4
D1
D2
D3
D4
MSB
Data 1
Data 2
Data 3
Data 4
Data 5
Data 6
LSB
EN
SCK
SDA
M1
M2
M3
M4
D1
D2
D3
D4
Control data input sequence
■
Mode selection
Mode data
0H
2H
4H
5H
EH
Other
Mode
Reset
DIN1 to 4 dimming
DIN5 dimming
LED ON
Reset
NPC test
M1-M2-M3-M4
L-L-L-L
L-L-H-L
L-H-L-L
L-H-L-H
H-H-H-L
−
SEIKO NPC CORPORATION —8
SM8134A
Mode data “0H”: Reset register
Mode data “EH”: Reset register
Setting data
D1
D2
D3
D4
High
All system data reset and standby
Low
Reset mode is selected if EN goes LOW 4 clock cycles after 0H or EH mode select data is input, regardless of
when power is applied or the parameter set data bits. When reset mode is selected, all data input previously is
reset, thus dimming and control data must be reentered.
Mode data “2H”: DIN1 to 4 dimming register
Mode data “4H”: DIN5 dimming register
Setting data
D1
D2
D3
D4
DIN1 to 4
DIN5
Unit
0H
Low
Low
Low
Low
0
0
mA
1H
Low
Low
Low
High
2
10
mA
2H
Low
Low
High
Low
4
20
mA
3H
Low
Low
High
High
6
30
mA
4H
Low
High
Low
Low
8
40
mA
5H
Low
High
Low
High
10
50
mA
6H
Low
High
High
Low
12
60
mA
7H
Low
High
High
High
14
70
mA
8H
High
Low
Low
Low
16
80
mA
9H
High
Low
Low
High
18
90
mA
AH
High
Low
High
Low
20
100
mA
BH
High
Low
High
High
22
110
mA
CH
High
High
Low
Low
24
120
mA
DH
High
High
Low
High
26
130
mA
EH
High
High
High
Low
28
140
mA
FH
High
High
High
High
30
150
mA
Note. “H”: Hexadecimal
Note. Target values only. Current rating accuracy is not guaranteed.
D1 to D4 setting data bits control the LED current in 15 steps.
Mode data “5H”: LED ON register
Setting data
D1
D2
D3
D4
High
DIN1 to 4 ON
−
DIN5 ON
−
Low
DIN1 to 4 OFF
−
DIN5 OFF
−
This register controls the DIN1 to 4 and DIN5 ON/OFF state. Each state is ON when the corresponding bit is
HIGH, and OFF when LOW. Each circuit starts when the corresponding bit in address 5H (D1 or D3) is set
HIGH, transferring from standby mode. It is recommended that these data settings be held LOW when possible
to control current consumption.
SEIKO NPC CORPORATION —9
SM8134A
Thermal Shutdown Circuit (Overheating Protection)
The thermal shutdown circuit operates whenever the IC temperature exceeds approximately 170°C for whatever reason. VOUT output recommences when the IC temperature falls below approximately 150°C. In that
case, the setting register is saved.
Under Voltage Lockout Circuit (UVLO)
When a VIN voltage falls below the 1.9V (typ), the under voltage lockout circuit operates, initializing all the
registers to logic 0. In this mode, all previous data is reset, thus all dimming and LED control data must be
input again.
VOUT Output Circuit Mode Switching
The SM8134A switches between 3 output states: standby mode (standby state), ×1.0 mode (VIN through
mode), and ×1.5 mode (×1.5 charge pump boost). This automatically adjusts the VOUT output to match the
drive LED characteristics and reduces the total power dissipation. Switching to and from ×1.0 and ×1.5 mode
occurs automatically in an internal circuit, and cannot be controlled using an external input.
Switching to standby mode
The internal circuit operating mode switches from ×1.0/×1.5 mode to standby mode when Reset resistor (mode
data “0H”, “EH”) was input, suppressing current consumption.
Switching from ×1.0 mode to ×1.5 mode
If the LED drive current set by serial interface can be driven without boosting the VIN input voltage, the VOUT
output operates in ×1.0 mode. In other words, if sufficient current flows even with the LED forward-direction
voltage drop “VF”, then VOUT is less than 4.9V. Operation in the more efficient ×1.0 mode reduces the total
power dissipation and extends the battery drive time. And if low “VF” LEDs are used or the LED drive current
setting is LOW, the operating time in ×1.0 mode is also extended.
1.0 mode
(high efficiency)
1.5 mode
(low efficiency)
1.0 mode
(high efficiency)
1.5 mode
(low efficiency)
High VF LED
Low VF LED
High
VIN input
Low
VOUT mode switching time comparison due to drive LED “VF” variation
If the VIN voltage falls or LED drive current set by serial interface increases such that the LED drive current is
too low in ×1.0 mode, then the LED drive circuit low-current detector operates, the VOUT output is automatically switched to ×1.5 mode, and the charge pump boosts the output voltage. This occurs even if only one LED
low-current condition is detected among the 5-channel LED drive circuits, thus it is recommended that LEDs
have small “VF” variation to optimize the total efficiency.
SEIKO NPC CORPORATION —10
SM8134A
VIN
input voltage
1.0
Low ILED
detector
1.5 threshold
(1)
Low ILED
detected
VOUT mode
(2)
1.0 mode
1.5 mode
4.9V
VOUT
output voltage
(3)
VIN voltage drop and VOUT output voltage
(1) When VIN falls, VOUT cannot overcome the LED “VF” rating, causing insufficient current flows and the
ILED low-current signal becomes active.
(2) When the ILED low-current condition is detected, the VOUT output circuit switches to ×1.5 mode (charge
pump mode).
(3) Prior to switching to ×1.5 mode, the VOUT voltage may be lower than 4.9V but sufficient current is supplied to the LED.
If after startup, the LED connected to a DIN pin is switched, the LED connection detector circuit flags an error,
and correct mode switching may not occur. If the DIN pin does not control the LED drive current, the low-current detector does not operate and the device cannot switch to ×1.5 mode.
SEIKO NPC CORPORATION —11
SM8134A
Switching from ×1.5 mode to ×1.0 mode
VF increases immediately after the LED current starts to flow, and then decreases as the LED temperature
increases due to the heating effect of the current flow. It can take about 10 seconds for the LED temperature to
stabilize and for VF to reach equilibrium, and VF may fluctuate more than 200mV. The VF fluctuation is
affected by the ambient temperature and LED current setting, and has a large affect on the automatic mode
switching voltage tolerances. To counter the effects of VF fluctuation, the SM8134A outputs a mode reset signal once every 1.4 seconds which automatically switches the output mode to ×1.0, and then a determination is
made whether to make the ×1.0 → ×1.5 mode switch.
1.4sec/cycle
(1)
Mode reset
(2)
VOUT mode
1.5 mode
Mode hold
L: hold
1.0 mode
min 80µs
max 200µs
(3)
ILED detector
ignore
VOUT
output voltage
4.9V (4)
Low ILED
detector
(5)
Switching from ×1.5 to ×1.0 mode due to the mode reset signal
(1) Mode reset signal is output once every 1.4 seconds.
(2) Switching from ×1.5 to ×1.0 mode due to the mode reset signal pulse.
(3) The mode hold time of 200µs (max) starts when output switches to ×1.0 mode. During this interval, the
mode is not switched even if an ILED undercurrent condition is detected.
(4) If VIN is low, the VOUT voltage momentarily drops because the boost function stops as a result of switching
to ×1.0 mode.
(5) The ILED undercurrent signal is ignored during the mode hold time, and the mode only switches in
response to the detector output after the mode hold time expires.
SEIKO NPC CORPORATION —12
SM8134A
For example, if the VIN voltage is low and the VOUT output voltage in ×1.0 mode does not provide sufficient
drive current, then the mode reset will cause a LED undercurrent condition. The LED undercurrent detector
circuit will output an LED undercurrent signal immediately after the switch to ×1.0 mode, but the output will
stay in ×1.0 mode and not return to ×1.5 mode for the duration of the mode hold time. Consequently, the VOUT
output is not boosted during the 85µs (min) to 200µs (max) mode hold time and the voltage drops and the LED
brightness is reduced. However, the LEDs are OFF for a maximum of 200µs only, and this is not discernible to
the naked eye and thus is not a problem.
1.0
1.5 threshold
VIN input voltage
Mode reset
(1.4sec/cycle)
Mode hold
(H: hold)
1.4sec
max
200µS
VOUT mode
(H: 1.5, L: 1.0)
4.9V
VOUT
output voltage
Low ILED detector
(H: low ILED)
VOUT drop due to the mode reset single
SEIKO NPC CORPORATION —13
SM8134A
STARTUP SEQUENCE
After power is applied to the SM8134A or when a reset input occurs (reset register mode setting), the internal
power-ON reset circuit initializes all registers to their default value of 0. Consequently, all required data for
LED drive operation must be input using the serial interface. The registers can be addressed in arbitrary
sequence. Note that the registers are set in the same sequence as they are addressed.
Example 1. Set LED1 to LED4 to 20mA drive without group setting
Set EN HIGH, input “2AH” using the serial interface, set EN LOW (LED1 to 4 current setting 20mA), set EN
HIGH, input “58H”, set EN LOW, LED1 to LED4 turn ON after the soft start ends.
Set LED1 to 4 current 20mA
LED1 to 4 ON
EN
2
SDA
0
0
A
1
0
1
0
5
1
0
0
1
8
0
1
1
0
0
0
SCK
Soft start time
LED1 to 4
20mA
EN = High
Send serial data "2AH"
2: DIN1 to 4 dimming command
A: Dimming data (20mA)
EN = Low
EN = High
Send serial data "58H"
5: LED ON command
8: LED1 to 4 ON
EN = Low
Example 1 input waveform
SEIKO NPC CORPORATION —14
SM8134A
Example 2. Set LED1 to LED4 to 20mA and LED5 to 120mA drive
Input “2AH” (LED1 to 4 current setting 20mA), “4CH” (LED5 current setting 120mA), “58H” (LED1 to 4
ON) on successive EN cycles using the serial interface. LED1 to LED4 turn ON after the soft start ends. Then
input “5AH” (LED1 to 5 ON) and in addition to LED1 to LED4, LED5 turns ON.
Set LED1 to 4 current 20mA
Set LED5 current 120mA
LED1 to 4 ON
LED1 to 5 ON
EN
2
SDA
0
0
A
1
0
1
0
5
1
0
0
1
8
0
1
1
0
4
0
0
0
1
C
0
0
1
1
5
0
0
0
1
A
0
1
1
0
1
0
SCK
20mA
LED1 to 4
Soft start time
120mA
LED5
Soft start time
EN = High
Send serial data "2AH"
2: DIN1 to 4 dimming command
A: Dimming data (20mA)
EN = Low
EN = High
Send serial data "58H"
5: LED ON command
8: LED1 to 4 ON
EN = Low
EN = High
Send serial data "4CH"
4: DIN5 dimming command
C: Dimming data (120mA)
EN = Low
EN = High
Send serial data "5AH"
5: LED ON command
A: LED1 to 4 ON, LED5 ON
EN = Low
Example 2 input waveform
SEIKO NPC CORPORATION —15
SM8134A
Example 3. Set LED1 to LED4 to 30mA drive, and then change LED 1 to LED4 to12mA
drive and set LED5 to 150mA drive
Input “2FH” (LED1 to 4 current setting 30mA) and “58H” (LED1 to 4 ON) using the serial interface. LED1 to
LED4 turn ON after the soft start ends. Then input “26H” (LED1 to 4 current setting 12mA), the current of
LED1 to LED4 change to 12mA. Moreover input “4FH” (LED5 current setting 150mA) and “5AH” (LED1 to
5 ON), LED5 turns ON in addition to LED1 to LED4. The total current of LED1 to LED5 should be set not
exceeding 200mA.
Set LED1 to 4 current 30mA
Set LED1 to 4 current 12mA
LED1 to 4 ON
Set LED5 current 150mA
LED1 to 5 ON
EN
2
SDA
0
0
F
1
0
1
1
5
1
1
0
1
8
0
1
1
0
2
0
0
0
0
6
1
0
0
1
4
1
0
0
1
F
0
0
1
1
5
1
1
0
1
A
0
1
1
0
1
0
SCK
30mA
LED1 to 4
12mA
Soft start time
150mA
LED5
Soft start time
EN = High
Send serial data "2FH"
2: DIN1 to 4 dimming command
F: Dimming data (30mA)
EN = Low
EN = High
Send serial data "58H"
5: LED ON command
8: LED1 to 4 ON
EN = Low
EN = High
Send serial data "26H"
2: DIN1 to 4 dimming command
6: Dimming data (12mA)
EN = Low
EN = High
Send serial data "4FH"
4: DIN5 dimming command
F: Dimming data (150mA)
EN = Low
EN = High
Send serial data "5AH"
5: LED ON command
A: LED1 to 4 ON, LED5 ON
EN = Low
Example 3 input waveform
SEIKO NPC CORPORATION —16
SM8134A
TYPICAL APPLICATION CIRCUIT
In circuits where the SM8134A logic-level inputs would become open circuit (floating) when the microcontroller supply stops, pull-down resistors should be connected to each logic-level signal input.
C1
1.0µF
C2
1.0µF
C1M C1P
C2M C2P
2.7 to 4.6V
C4
4.7µF
VIN
VOUT
Charge pump
1/ 1.5
C3
4.7µF
Back Light
Max 30mA
Thermal
shut down
4ch
DIN1
Output voltage
control
DIN2
UVLO
Current
control
&
Current
detect
SCK
SDA
Microcontroller
EN
Control
logic
DIN3
DIN4
DIN5
Flash
Max 150mA
Pull down
GND
PGND
Note. If the driving LEDs are less than 5 pcs, the unused DIN pins should be connected to GND.
SEIKO NPC CORPORATION —17
SM8134A
PERIPHERAL PARTS
About the External Capacitors
The best capacitors for use with the SM8134A are multi-layer ceramic capacitors. When selecting a multi-layer
ceramic capacitor, only X5R and X7R dielectric types are strongly recommended, since the loss of capacitance
in various conditions is less than other types such as Z5U and Y5V. The much loss of capacitance in various
conditions may cause the output voltage unstable.
Table. The EIA three digit "TC" code
Lower temperature limit
High temperature limit
Maximum allowable capacitance
change from + 25°C (0V DC)
X = −55°C
5 = +85°C
F = ± 7.5%
Y = −30°C
6 = +105°C
P = ± 10%
Z = +10°C
7 = +125°C
R = ± 15%
8 = +150°C
S = ± 22%
T = +22%/−33%
U = +22%/−56%
V = +22%/−82%
For example
: X5R
About the Input Capacitor "C4"
The parts layout of PCB may merely cause the “VOUT” output voltage unstable. In this case, increasing the
“C4” input capacitance value or adding another capacitor on the VIN input line is effective to solve the unstable output voltage.
FOOTPRINT PATTERN
3.6 ± 0.1
2.2 ± 0.1
0.
32
0.25 ± 0.05
0.7 ± 0.1
2.2 ± 0.1
0.5 × 3 = 1.5 ± 0.05
3.6 ± 0.1
0.5 × 3 = 1.5 ± 0.05
SEIKO NPC CORPORATION —18
SM8134A
Please pay your attention to the following points at time of using the products shown in this document.
The products shown in this document (hereinafter “Products”) are not intended to be used for the apparatus that exerts harmful influence on
human lives due to the defects, failure or malfunction of the Products. Customers are requested to obtain prior written agreement for such
use from SEIKO NPC CORPORATION (hereinafter “NPC”). Customers shall be solely responsible for, and indemnify and hold NPC free and
harmless from, any and all claims, damages, losses, expenses or lawsuits, due to such use without such agreement. NPC reserves the right
to change the specifications of the Products in order to improve the characteristic or reliability thereof. NPC makes no claim or warranty that
the contents described in this document dose not infringe any intellectual property right or other similar right owned by third parties.
Therefore, NPC shall not be responsible for such problems, even if the use is in accordance with the descriptions provided in this document.
Any descriptions including applications, circuits, and the parameters of the Products in this document are for reference to use the Products,
and shall not be guaranteed free from defect, inapplicability to the design for the mass-production products without further testing or
modification. Customers are requested not to export or re-export, directly or indirectly, the Products to any country or any entity not in
compliance with or in violation of the national export administration laws, treaties, orders and regulations. Customers are requested
appropriately take steps to obtain required permissions or approvals from appropriate government agencies.
SEIKO NPC CORPORATION
15-6, Nihombashi-kabutocho, Chuo-ku,
Tokyo 103-0026, Japan
Telephone: +81-3-6667-6601
Facsimile: +81-3-6667-6611
http://www.npc.co.jp/
Email: [email protected]
NC0417BE
2006.04
SEIKO NPC CORPORATION —19