SM8136A
White LED Driver IC
OVERVIEW
The SM8136A is a charge pump type white LED driver. It can drive 1 to 3 backlight white LED connected in
parallel, making it ideal for portable devices with small LCD. The charge pump switches between
×1
bypass
mode to
×1.5
boost mode in response to LED drive current requirements. The boost switching occurs in
response to the drive current of all the connected LED and thus supports variations in LED forward-bias volt-
age drop (VF). Besides, the detection of switching is repeated in approx. 1sec-cycle by mode reset action, the
SM8136A can respond to temporary variation of supply voltage. These ingenuities on switching detection can
prolong the battery life to the fullest extent. Each LED drive current is controlled by a 3-channel LED drive
current control circuit.
FEATURES
I
PINOUT
(Top view)
DIN1
DIN2
DIN3
NC
GND
VIN
C1M
C2M
C2P
EN
VOUT
C1P
I
I
I
I
I
I
I
I
I
I
I
2.00
±
0.07
A
B
1.00
0.40
×
2 = 0.80
±
0.05
0.60
I
12
8−C0.08
1
1
12
I
I
I
I
I
I
I
I
I
Cellular phone
PDA
Portable games
Portable audio equipment
Handy terminal
Digital still camera
Digital video camera
LCD panel back light
White LED driving
C0.30
0.60
0.70
±
0.05
0.10 S A B
0.05 max
0.75 max
0.18
±
0.05
φ0.05
M S A B
0.10 S
S
0.05 S
0.40
ORDERING INFORMATION
Device
SM8136AB
Package
12-pin QFN
SEIKO NPC CORPORATION —1
1.00
APPLICATIONS
2.00
±
0.07
0.25
±
0.07
Top view
Bottom view
0.40
×
2 = 0.80
±
0.05
Battery life extension by automatic charge pump
switch between
×1
to
×1.5
according to the detec-
tion of the LED drive current
Controlling 1 to 3 lights of white LED connected
in parallel
1-wire input controlling
ON/OFF and brightness control by signal control-
ling of EN pin
Soft start circuit built-in
Input voltage range
No-load current (I
OUT
= 0mA): 2.7 to 4.6V
Load current (I
OUT
= 60mA): 3.0 to 4.6V
Maximum output voltage: 5.0V (typ)
Maximum output current: 60mA (typ)
Quiescent current
Not-switching (×1 mode): 0.3mA (typ)
Switching (
×
1.5 mode): 1.0mA (typ)
Standby current: 0.01µA (typ)
Operating frequency (boost mode): 1.0MHz (typ)
LED drive current accuracy between channel:
± 5.0%
Package: 12-pin QFN
PACKAGE DIMENSIONS
(Unit: mm)
SM8136A
BLOCK DIAGRAM
C1M C1P C2M C2P
VIN
Charge pump
1/ 1.5
VOUT
Mode control
&
Output voltage control
&
Protection
Current
control
&
Current
detect
DIN1
DIN2
DIN3
EN
Control
logic
NC
GND
(open at any time)
PIN DESCRIPTION
Number
1
2
3
4
5
6
7
8
9
10
11
12
Name
C1M
C2M
C2P
C1P
VOUT
EN
DIN3
DIN2
DIN1
NC
PGND
VIN
I/O
–
–
–
–
O
I
O
O
O
–
–
–
Description
Charge pump boost capacitor connection 1M
Charge pump boost capacitor connection 2M
Charge pump boost capacitor connection 2P
Charge pump boost capacitor connection 1P
LED drive voltage output
Enable/LED drive current setting (High active)
LED drive current control output 3
(connect
to ground when not used)
LED drive current control output 2
(connect
to ground when not used)
LED drive current control output 1
(connect
to ground when not used)
No connection
Ground
Supply voltage input
SEIKO NPC CORPORATION —2
SM8136A
SPECIFICATIONS
Absolute Maximum Ratings
GND = 0V
Parameter
VIN voltage range
Input voltage range
Output voltage range
VOUT output current
Power dissipation
Junction temperature
Storage ambient temperature range
*1. When mounted on a 4-layer board.
Note. The device may suffer breakdown if any one of these parameter ratings is exceeded.
Symbol
V
IN
V
EN
V
DIN1 to 3
V
OUT
I
OUT
P
D
T
JMAX
T
stg
Rating
−0.3
to 6.0
–0.3 to V
IN
+ 0.3
–0.3 to V
IN
+ 0.3
6.0
500
800
(Ta
= 25°C)
*1
+125
−55
to +125
Unit
V
V
V
V
mA
mW
°C
°C
1000
Power dissipation [mW]
800
600
400
200
0
25
35
45
55
65
Operating temperature [°C]
75
85
Package power dissipation when mounted on 4-layer board
Recommended Operating Conditions
GND = 0V
Rating
Parameter
Pin
Symbol
V
IN0
V
IN
Input voltage range
Ambient temperature range
EN
−
V
ES
Ta
Conditions
min
Supply voltage range
VIN
I
OUT
= 0mA
I
OUT
= 60mA
Logic-level inputs
2.7
3.3
0
−40
typ
3.6
3.6
−
−
max
4.6
4.6
V
IN
+85
V
V
V
°C
Unit
SEIKO NPC CORPORATION —3
SM8136A
Electrical Characteristics
V
IN
= 3.6V, GND = 0V, Ta = 25°C unless otherwise noted.
Rating
Parameter
Standby current
Quiescent current 1
VIN
Quiescent current 2
Output voltage
Maximum output current
Operating frequency
Internal power-ON reset time
*1
Power-ON rise time
Soft start time
LED drive pin leakage current
LED drive current
LED drive current accuracy
LED drive pin voltage
×1.0 ↔ ×1.5
mode switching
threshold voltage
EN hold time
*1*2
EN HIGH-level input time
*1
EN LOW-level input time
*1*2
VOUT
VOUT
C1M
EN
EN, VIN
DIN1 to 3
DIN1 to 3
DIN1 to 3
DIN1 to 3
DIN1 to 3
VIN
EN
EN
EN
Pin
VIN
Symbol
I
STB
I
DD1
I
DD2
V
OUT
I
OUT
f
OSC
T
POR
T
PR
T
SS
I
Leak1 to 3
I
LED1 to 3
∆I
LED
V
DIN1 to 3
V
TH1.0 to 1.5
T
CEH
T
ENH
T
ENL
V
IH
V
IL
Logic input current
*1. Design guaranteed value
*2.
When shutdown
EN
When dimming
EN
> 1.5msec
4µsec to 500µsec
Condition
min
Standby mode
×1.0
mode, I
OUT
= 0mA
×1.5
mode, I
OUT
= 0mA
×1.5
mode, V
IN
= 3.6V, I
OUT
= 0mA
×1.5
mode, V
IN
= 3.0V, I
OUT
= 60mA
×1.5
mode
×1.5
mode switching frequency
Rest time from when power is applied
EN = VIN, time from 0.3V to 2.7V
EN startup
→
I
LED
rising edge
Standby mode, DIN pin = 5.0V
×1.0
mode (3-channel average value)
×1.0
mode, relative accuracy between
channels at I
LED
maximum settings
×1.0
mode, I
LED
= 20mA
VF (LED) = 3.3V, I
LED
= 20mA
Time from when EN = LOW until
shutdown
EN input pulse HIGH-level minimum
pulsewidth
EN input pulse LOW-level pulsewidth
range
HIGH-level input voltage range
LOW-level input voltage range
Pull-down pin, EN pin = 3.6V
EN pin = 0V
–
–
–
4.5
–
60
800
–
–
–
–
18.0
–5.0
–
–
0.50
4.0
4.0
1.4
–
–
–1.0
typ
0.01
0.3
1.0
5.0
3.5
–
1000
0.05
–
2.00
0.01
20.0
–
120
3.46
1.00
–
–
–
–
5.0
–
max
1.00
1.0
2.0
5.5
–
–
1200
1.00
50
3.00
1.00
22.0
+5.0
–
–
1.50
–
500
–
0.3
10.0
–
Unit
µA
mA
mA
V
V
mA
kHz
ms
µs
ms
µA
mA
%
mV
V
ms
µs
µs
V
V
µA
µA
Logic input voltage
EN
EN
I
IH
I
IL
SEIKO NPC CORPORATION —4
SM8136A
FUNCTIONAL DESCRIPTION
LED Drive Current Setting
The SM8136A LED drive current can be set using the EN pin. The EN input is used to enable/disable circuit
operation. It also is used by a built-in counter that counts the number of input pulses in order to set the LED
current value. The built-in counter is a 4-bit counter for 16-step adjustment (DATA = 1 to 16). On the 16th
pulse (DATA = 16), the LED current drive circuit shuts down and LED current is zero. On the 17th pulse
(DATA = 1), the current returns to the maximum value. As the initial pulse (DATA = 1) sets the current to the
maximum value, the device can also be used in applications that do not support pulsed input.
Table 1. EN input pulse count and LED current setting values
DATA
EN
pulse
count
I
LED
[mA]
1
1
17
20.00
2
2
18
18.7
3
3
19
17.3
4
4
20
16.0
5
5
21
14.7
6
6
22
13.3
7
7
23
12.0
8
8
24
10.7
9.3
8.0
6.7
5.3
4.0
2.7
1.3
0
9
9
10
10
11
11
12
12
13
13
14
14
15
15
16
16
EN Input Signal and LED Current Setting (Initialization)
On the first rising edge of EN, the internal startup signal goes HIGH and LED current will start to flow after the
soft start time has elapsed. As the LED current setting is adjusted by counting the number of input pulses on
EN, the EN input voltage must be switched HIGH
→
LOW
→
HIGH repeatedly to set the current to a lower
value. After the desired value is achieved, the EN input voltage is held HIGH to maintain the LED current set-
ting. If the EN input goes LOW, the LED current does not flow. The EN data input circuit operates even though
the LED current does not flow during the soft start interval, but as long as the current value is set during the soft
start interval the LED drive circuits will start to drive the LEDs with that constant current setting. However,
note that the setting is valid only after the power-ON reset when the VIN supply is applied. Accordingly, allow
1ms or more after connecting the VIN supply before setting the current value using the EN input.
1
EN input
signal
1
I
LED1-3
2
3
4
5
6
7
8
2
3
4
5
6
7
8
EN input signal and LED current setting
I
LED current setting is determined by the number of EN input signal rising edges. Furthermore, no LED cur-
rent flows until the soft start time has elapsed.
SEIKO NPC CORPORATION —5
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