NPC SM8133B_06

SM8133B
White LED Driver IC
OVERVIEW
The SM8133B is a charge pump type white LED driver. It can drive 1 to 6 backlight white LED connected in
parallel and 1 flash white LED. The output voltage circuit has a 3.0V LDO (Low Dropout Regulator), 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 7-channel LED drive current control
circuit. The 6 backlight channels can be subdivided into 2 groups, with each group having independent dimming and lighting control. The backlight grouping, backlight LED drive current and ON/OFF control, flash
LED drive current and ON/OFF control, and LDO output ON/OFF control are all set by 3-wire serial interface
data input. Also, the RESETB pin can be connected to the microcontroller supply for a system-wide shutdown
function.
FEATURES
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Noise reduction due to charge pump boost circuit
Automatic charge pump switching to conserve
power
Drives 1 to 6 backlight white LED
(30mA/ch at maximum setting)
Drives a flash white LED
(150mA at maximum setting)
Backlight and flash white LED brightness
adjustment
Group settings for 2-group backlight lighting
control
3-wire serial input interface for all setting and
control
3.0V output LDO circuit built-in
Shutdown function by RESETB pin
Soft start circuit built-in
Thermal protection circuit built-in
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APPLICATIONS
■
■
■
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Cellular phone
Digital still camera
PDA
Portable games
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 = 200mA): 3.3 to 4.6V
Quiescent current
• LDO only: 0.3mA (typ)
• Not -switching (×1.0 mode): 0.5mA (typ)
• Switching (×1.5 mode): 2.5mA (typ)
Standby current: 0.01µA (typ)
Operating frequency: 750kHz (typ)
Backlight LED current: 30mA/ch (typ)
Flash LED current: 150mA (typ)
All LED total maximum current: 200mA (typ)
Backlight LED current matching (ILED = 30mA)
: ± 3%
Flash LED current accuracy (ILED = 150mA)
: ± 5%
LDO (Low Dropout Regulator) output voltage
: 3.0V ± 2%
Packages: 20-pin QFN
WL-CSP (under development)
ORDERING INFORMATION
Device
Package
SM8133BB
20-pin QFN
SM8133BW
WL-CSP
SEIKO NPC CORPORATION —1
SM8133B
PACKAGE DIMENSIONS
(Unit: mm)
QFN-20
4.20 ± 0.20
4.00 ± 0.10
20
4.20 ± 0.20
4.00 ± 0.10
1
0.50
1.00MAX
+ 0.03
0.02 − 0.02
0.05
0.22 ± 0.05
0.22
0.60 ± 0.10
0.05 M
WL-CSP (under development)
Top view
Bottom view
0.48 ± 0.03
0.4
2.56 ± 0.03
0.68 ± 0.03
B
D
C
B
A
1 2 3 4 5
20 − φ0.2 ± 0.03
0.08 ± 0.03
S
0.09 ± 0.007
0.55 ± 0.02
2.56 ± 0.03
0.4
φ0.05 M S AB
A
0.06 S
SEIKO NPC CORPORATION —2
SM8133B
PINOUT
(Top view)
WL-CSP (under development)
SDA
SCK
RESETB
VOUT
LDOUT
QFN-20
15 14 13 12 11
EN
DIN7
DIN6
DIN5
GND
16
17
18
19
20
10
9
8
7
6
D
C
B
A
VIN
C2P
C2M
C1M
C1P
5 4 3 2 1
DIN4
DIN3
DIN2
DIN1
PGND
1 2 3 4 5
PIN DESCRIPTION
Number
Name
I/O
D1
DIN4
O
LED drive current control output 4 (connect to ground when not used)
2
C1
DIN3
O
LED drive current control output 3 (connect to ground when not used)
3
B1
DIN2
O
LED drive current control output 2 (connect to ground when not used)
4
B2
DIN1
O
LED drive current control output 1 (connect to ground when not used)
5
A2
PGND
–
Charge pump ground connection
6
A1
C1P
–
Charge pump capacitor connection 1P
7
A3
C1M
–
Charge pump capacitor connection 1M
8
B3
C2M
–
Charge pump capacitor connection 2M
9
B4
C2P
–
Charge pump capacitor connection 2P
10
A4
VIN
–
Voltage supply
11
A5
LDOUT
O
LDO output (leave open circuit when not used)
12
B5
VOUT
O
LED drive voltage output
13
C5
RESETB
I
Reset signal input (internal reset when RESETB is LOW)
14
C4
SCK
I
Serial data clock input
15
D5
SDA
I
Serial data input
16
D4
EN
I
Serial interface enable input
17
C3
DIN7
O
LED drive current control output 7 (connect to ground when not used)
18
D3
DIN6
O
LED drive current control output 6 (connect to ground when not used)
19
D2
DIN5
O
LED drive current control output 5 (connect to ground when not used)
20
C2
GND
–
Ground
QFN-20
WL-CSP
1
Description
SEIKO NPC CORPORATION —3
SM8133B
BLOCK DIAGRAM
C1M C1P C2M C2P
VIN
Charge pump
1/ 1.5
VOUT
Mode control
&
Output voltage control
&
Protection
DIN1
DIN2
Current
control
&
Under
current
detector
Thermal
shut down
DIN3
DIN4
DIN5
RESETB
DIN6
SCK
Control
logic
DIN7
SDA
EN
LDO 3V
&
Protection
GND
LDOUT
PGND
SEIKO NPC CORPORATION —4
SM8133B
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 7
–0.3 to VIN + 0.3
V
VOUT
5.5
V
VOUT output current
IOUT
500
mA
LDO output current
ILDO
200
mA
PD
1429 (Ta = 25°C)*1
mW
TJMAX
+125
°C
Tstg
−55 to +125
°C
Supply voltage range
Input voltage range
Output voltage range
Power dissipation
Junction temperature
Storage temperature range
*1. When mounted on a 34 × 40 × 1.6mm glass epoxy board, the power dissipation is related to the operating temperature
by the following equation.
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Maximum junction temperature: TMAX = 125°C
Operating temperature: Ta [°C]
Thermal resistance: θJ = 70°C/W
PD =
1600
1429
Power dissipation [mW]
■
(TMAX − Ta)
θJ
1143
1200
857
800
571
400
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
3.0
3.6
4.6
V
VIN3
×1.5 mode, IOUT = 200mA
3.3
3.6
4.6
V
EN, SCK,
SDA,
RESETB
VES
Each logic-level pin
0
−
VIN
V
−
Ta
−30
−
+85
°C
VIN
SEIKO NPC CORPORATION —5
SM8133B
Electrical Characteristics
DC Characteristics
GND = PGND = 0V, VIN = 3.6V, Ta = 25°C unless otherwise noted.
Rating
Parameter
Standby current
Quiescent current
Pin
VIN
VIN
Symbol
Condition
Unit
min
typ
max
ISTB
Standby mode
–
0.01
1.00
µA
IDD1
LDO-only operating, no load
–
0.3
0.7
mA
IDD2
×1.0 mode, no load
–
0.5
1.0
mA
IDD3
×1.5 mode, no load
–
2.5
4.0
mA
Maximum output voltage
VOUT
VOUT
×1.5 mode VOUT maximum voltage
4.8
5.0
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
–
0.02
0.10
ms
Soft start time
DIN1 to 7
TSS
Time between EN signal falling edge
and LED turning ON
–
1.3
3.0
ms
LED drive pin leakage current
DIN1 to 7
ILEAK1 to 7
Standby mode, VDIN1 to 7 = 5.0V
–
0.01
1.00
µA
LED drive current matching
DIN1 to 6
∆ILED
×1.0 mode, matching between channels
with ILED1 to 6 maximum setting
–3.0
–
+3.0
%
LED maximum drive current 1
DIN1 to 6
ILED1 to 6
×1.0 mode, ILED1 to 6 maximum setting
27.0
30.0
33.0
mA
LED drive pin voltage 1
DIN1 to 6
VDIN1 to 6
ILED1 to 6 maximum setting
80
120
150
mV
LED maximum drive current 2
DIN7
ILED7
×1.5 mode, ILED7 maximum setting
142.5
150.0
157.5
mA
LED drive pin voltage 2
DIN7
VDIN7
IDIN7 maximum setting
225
300
375
mV
LDO output voltage
LDOUT
VLDO
VIN = 3.6V, ILDO = 100mA
2.94
3.00
3.06
V
LDO maximum output current
LDOUT
ILDO
VIN = 3.0V, VLDO = 2.85V
100
–
–
mA
LDO input stability
LDOUT
∆VOUT1
3.3V ≤ VIN ≤ 4.6V, ILDO = 30mA
–
–
1.0
%/V
LDO load stability
LDOUT
∆VOUT2
VIN = 3.6V, 10µA ≤ ILDO ≤ 80mA
–
–
100
mV
LDO overcurrent protection
circuit operating current
LDOUT
IOS
VIN = 3.6V
120
230
360
mA
Thermal protection circuit
operating temperature*1
–
TSD
Not in test mode
–
180
–
°C
Thermal protection circuit
hysteresis*1
–
TSDHYS
Not in test mode
–
20
–
°C
Logic-level input voltage
EN, SCK,
SDA,
RESETB
Logic-level input current
EN, SCK,
SDA,
RESETB
VIH
HIGH-level input voltage range
1.8
–
–
V
VIL
LOW-level input voltage range
–
–
0.6
V
Hysteresis voltage width
–
0.3
0.5
V
IIL
EN = SCK = SDA = RESETB = VIN
–
–
1.0
µA
IIH
EN = SCK = SDA = RESETB = GND
–1.0
–
–
µA
VIHYS
*1. Design guaranteed value
SEIKO NPC CORPORATION —6
SM8133B
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 —7
SM8133B
VOUT EFFICIENCY
100
VOUT power efficiency [%]
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
4.4
4.6
VIN [V]
Efficiency of PIN vs. POUT
Backlight LED × 6pcs, ILED1 to 6 = 20mA,
Flash LED × 1pc, ILED7 = 0mA,
IOUT = 120mA, ILDO = 0mA
100
VOUT power efficiency [%]
90
80
VF = 3.2V
VF = 3.4V
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 6 = 15mA,
Flash LED × 1pc, ILED7 = 0mA,
IOUT = 45mA, ILDO = 0mA
SEIKO NPC CORPORATION —8
SM8133B
100
VOUT power efficiency [%]
90
80
VF = 3.2V
VF = 3.4V
70
VF = 3.6V
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 × 6pcs, ILED1 to 6 = 20mA,
Flash LED × 1pc, ILED7 = 80mA,
IOUT = 200mA, ILDO = 0mA
100
VOUT power efficiency [%]
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 6 = 15mA,
Flash LED × 1pc, ILED7 = 150mA,
IOUT = 195mA, ILDO = 0mA
SEIKO NPC CORPORATION —9
SM8133B
100
VOUT power efficiency [%]
90
80
VF = 3.2V
70
VF = 3.4V
VF = 3.6V
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 × 6pcs, ILED1 to 6 = 20mA,
Flash LED × 1pc, ILED7 = 80mA,
IOUT = 200mA, ILDO = 100mA
100
VOUT power efficiency [%]
90
80
VF = 3.2V
70
VF = 3.4V
VF = 3.6V
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 6 = 15mA,
Flash LED × 1pc, ILED7 = 150mA,
IOUT = 195mA, ILDO = 100mA
SEIKO NPC CORPORATION —10
SM8133B
FUNCTIONAL DESCRIPTION
Serial Interface
The SM8133B 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 SM8133B 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, CSK, and RESETB 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
1H
2H
3H
4H
Mode
Reset
Grouping
A group dimming
B group dimming
DIN7 dimming
M1-M2-M3-M4
L-L-L-L
L-L-L-H
L-L-H-L
L-L-H-H
L-H-L-L
Mode data
5H
6H
EH
FH
Other
Mode
LED ON
System settings
Reset
Serial input test
NPC test
M1-M2-M3-M4
L-H-L-H
L-H-H-L
H-H-H-L
H-H-H-H
−
SEIKO NPC CORPORATION —11
SM8133B
Mode data “0H”: Reset register
Mode data “EH”: Reset register
Setting data
D1
D2
D3
High
All system data reset
Low
System standby
D4
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 grouping, dimming, and control data must be reentered.
Mode data “1H”: Grouping register
Setting data
D1
D2
D3
D4
High
LED3 = B group
LED4 = B group
LED5 = B group
LED6 = B group
Low
LED3 = A group
LED4 = A group
LED5 = A group
LED6 = A group
LED1 and LED2 are always assigned to A group. When a setting data bit is LOW, A group is selected. When
HIGH, B group is selected.
Mode data “2H”: A group dimming register
Mode data “3H”: B group dimming register
Mode data “4H”: DIN7 dimming register
Setting data
D1
D2
D3
D4
Selected dimming
value
0H
Low
Low
Low
Low
0/15
1H
Low
Low
Low
High
1/15
2H
Low
Low
High
Low
2/15
3H
Low
Low
High
High
3/15
4H
Low
High
Low
Low
4/15
5H
Low
High
Low
High
5/15
6H
Low
High
High
Low
6/15
7H
Low
High
High
High
7/15
8H
High
Low
Low
Low
8/15
9H
High
Low
Low
High
9/15
AH
High
Low
High
Low
10/15
BH
High
Low
High
High
11/15
CH
High
High
Low
Low
12/15
DH
High
High
Low
High
13/15
EH
High
High
High
Low
14/15
FH
High
High
High
High
15/15
D1 to D4 setting data bits control the each group LED current in 15 steps. See “LED drive current”.
SEIKO NPC CORPORATION —12
SM8133B
Mode data “5H”: LED ON register
Setting data
D1
D2
D3
D4
High
A group ON
B group ON
DIN7 ON
LDO ON
Low
A group OFF
B group OFF
DIN7 OFF
LDO OFF
This register controls the A group, B group, DIN7, and LDO 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 is set
HIGH, transferring from standby mode. It is recommended that these 4 data settings be held LOW when possible to control current consumption.
Mode data “6H”: System register
Setting data
D1
D2
D3
D4
High
A group maximum
current = 15mA
B group maximum
current = 15mA
DIN7 maximum
current = 75mA
−
Low
A group maximum
current = 30mA
B group maximum
current = 30mA
DIN7 maximum
current = 150mA
−
Note. Target values only. Current rating accuracy is not guaranteed.
This register sets the maximum current drive for each group. For A and B group, LOW sets 30mA as the maximum, HIGH sets 15mA. For DIN7, LOW sets 150mA, HIGH sets 75mA as the maximum.
LED drive current (Hexadecimal)
A group
Dimming
register value
B group
DIN7
A group max.
current = 0
A group max.
current = 1
B group max.
current = 0
B group max.
current = 1
DIN7 max.
current = 0
DIN7 max.
current = 1
Unit
0H
0
0
0
0
0
0
mA
1H
2
1
2
1
10
5
mA
2H
4
2
4
2
20
10
mA
3H
6
3
6
3
30
15
mA
4H
8
4
8
4
40
20
mA
5H
10
5
10
5
50
25
mA
6H
12
6
12
6
60
30
mA
7H
14
7
14
7
70
35
mA
8H
16
8
16
8
80
40
mA
9H
18
9
18
9
90
45
mA
AH
20
10
20
10
100
50
mA
BH
22
11
22
11
110
55
mA
CH
24
12
24
12
120
60
mA
DH
26
13
26
13
130
65
mA
EH
28
14
28
14
140
70
mA
FH
30
15
30
15
150
75
mA
Note. “H”: Hexadecimal
Note. Target values only. Current rating accuracy is not guaranteed.
SEIKO NPC CORPORATION —13
SM8133B
LDO (Low Dropout Voltage Regulator)
Operation is controlled using the LDO register (LSB in address “5H”). When the LDO register is set to 1, a
regulated stable voltage is output from LDOUT. If the overcurrent protection circuit connected to LDOUT
detects a continuous overcurrent condition for approximately 200µs, the LDO output stops and then restarts
after a delay of approximately 1.4 seconds. At this point, if an overcurrent condition is detected again, the LDO
output stops. If the overcurrent condition is detected a total of 12 successive times (approximately 16.8 seconds), the LDO load is deemed to be abnormal and the LDO output stops completely. The abnormal load condition is released only by selecting reset mode operation.
Thermal Shutdown Circuit (Overheating Protection)
The thermal shutdown circuit operates whenever the IC temperature exceeds approximately 180°C for whatever reason. VOUT output recommences when the IC temperature falls below approximately 160°C.
RESETB Input (Internal Circuit Reset Signal)
If the microcontroller, which drives the serial data inputs, stops, the SM8133B logic-level signal inputs are left
floating and the SM8133B will most likely not transfer to standby mode normally. However, the RESETB pin
can be connected to the microcontroller supply pin, so that the SM8133B is reset automatically whenever the
voltage on RESETB drops. A pull-down resistor should be connected between RESETB and GND to avoid a
floating RESETB input with voltage applied to the VIN pin.
VOUT Output Circuit Mode Switching
The SM8133B switches between 3 output states: power-save 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.
SEIKO NPC CORPORATION —14
SM8133B
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 5.0V. 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 7-channel LED drive circuits, thus it is recommended that LEDs
have small “VF” variation to optimize the total efficiency.
VIN
input voltage
1.0
Low ILED
detector
1.5 threshold
(1)
Low ILED
detected
VOUT mode
(2)
1.0 mode
1.5 mode
5.0V
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 5.0V 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 —15
SM8133B
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 SM8133B 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
5.0V (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 —16
SM8133B
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)
5.0V
VOUT
output voltage
Low ILED detector
(H: low ILED)
VOUT drop due to the mode reset single
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SM8133B
STARTUP SEQUENCE
After power is applied to the SM8133B or when a reset input occurs (active-LOW input on RESETB or 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 LED6 to 30mA drive without group setting
Set EN HIGH, input “2FH” using the serial interface, set EN LOW (A group current setting 30mA), set EN
HIGH, input “58H”, set EN LOW (A group ON), LED1 to LED6 turn ON after the soft start ends.
Set A group current: 30mA (2FH)
A group ON (58H)
EN
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
SCK
SDA
Approx. 30mA
Soft start time
ILED1 to 6
Example 1 input waveform
Example 2. Set LED1 to LED4 to A group, LED5 and LED6 to B group, and individual
group brightness
Input “13H” using the serial interface (group setting), input “25H” (A group current setting 10mA), input
“3AH” (B group current setting 20mA), input “5CH” (A and B groups ON) on successive EN cycles. LED1 to
LED6 turn ON after the soft start ends.
Set grouping (13H)
LED1 to LED4 A group
LED5 to LED6 B group
Set A group current: 10mA (25H)
Set B group current: 20mA (3AH)
A group, B group ON (5CH)
EN
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
SCK
SDA
Soft start time Approx. 10mA
ILED1 to 4
Approx. 20mA
ILED5 to 6
Example 2 input waveform
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SM8133B
Example 3. Set LED1 to LED6 to 30mA drive, temporarily turn OFF, turn ON again,
and reset using RESETB input without group setting
Input “2FH”(A group current setting 30mA) and “58H” (A group ON) from the serial interface. LED1 to
LED6 turn ON after the soft start ends. While the LEDs are ON, input “50H” (A group OFF) to turn the LEDs
OFF and transfer the SM8133B to standby mode. The internal register setting “2FH” (A group current setting
30mA) data is retained during standby mode, so you need to input “58H” (A group ON) only to turn the LEDs
ON again. At this point, the charge pump soft start circuit operates again, taking a soft start time of approximately 1.3ms from when the data is input to when the LEDs turn ON. If RESETB is connected to the microcontroller power supply and the supply goes LOW, the SM8133B is reset, the LEDs turn OFF, and operation
transfers to standby mode.
RESETB
Reset
Reset mode
LED mode
LED ON mode
Set A Group current : 30mA (2FH)
Reset mode
A group ON (58H)
A group OFF (50H)
A group ON (58H)
EN
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
SCK
SDA
ILED1 to 6
Soft start time
Approx. 30mA
Soft start time
Approx. 30mA
Example 3 input waveform
SEIKO NPC CORPORATION —19
SM8133B
TYPICAL APPLICATION CIRCUIT
If the RESETB input is connected to the microcontroller power supply, the SM8133B is reset when microcontroller power supply stops, and operation transfers to standby mode. In circuits where the SM8133B 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
C1M C1P
VIN
2.7 to 4.6V
Battery
C4
2.2µF
C2
1.0µF
C2M C2P
VOUT
Charge pump
1/ 1.5
C3
2.2µF
Back Light
Max 30mA
6ch
DIN1
Mode control
&
Output voltage control
&
Protection
LDO for
microcontroller
power source
DIN2
DIN3
Current
control
&
Under
current
detector
Thermal
shut down
DIN4
DIN5
RESETB
DIN6
Pull down
VDD
SCK
Microcontroller
SDA
Control
logic
DIN7
EN
Pull down
Flash
Max 150mA
LDO 3V
&
Protection
GND
LDOUT
3V ± 2% (VIN ≥ 3.2V)
Max 100mA
C5
1.0µF
PGND
Note. If the driving LEDs are less than 7 pcs, the unused DIN pins should be connected to GND.
If the LDO is not used, LDOUT pin should be left open circuit.
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SM8133B
PERIPHERAL PARTS
About the External Capacitors
The best capacitors for use with the SM8133B 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.
QFN-20 Package
Package corner metals are not IC I/O pins. Don’t connect any lines to these corner metals.
Bottom view
SEIKO NPC CORPORATION —21
SM8133B
FOOTPRINT PATTERN
The optimum footprint varies depending on the board material, soldering paste, soldering method, and equipment accuracy, all of which need to be considered to meet design specifications.
(Unit: mm)
HE
HD
e
b3
l1
l2
QFN-20
4.2
4.2
0.5
0.30 ± 0.05
0.20 ± 0.05
0.70 ± 0.05
HE /2
Package
b3
HE
e
b3
l1
e
l2
l2
l1
HD /2
HD
SEIKO NPC CORPORATION —22
SM8133B
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]
NC0503CE
2006.04
SEIKO NPC CORPORATION —23