SM8135A
White LED Driver IC
OVERVIEW
The SM8135A is a charge pump type white LED driver. It can drive 1 to 4 backlight white LED connected in
parallel, making it ideal for portable devices with small LCD. The charge pump switches between
×1
bypass
mode,
×1.5
and
×2
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
SM8135A 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 4-channel LED drive
current control circuit. The LED drive current per channel is setup by external resistor. Moreover, the PWM
signal control of EN pin can realize nonstep brightness control (10% to 100%). The IC ON/OFF is controlled
by EN pin.
FEATURES
I
PINOUT
(Top view)
GND
NC
DIN3
DIN4
DIN2
DIN1
VOUT
C2P
C2M
PGND
C1P
C1M
ISET
EN
GND
VIN
I
I
I
I
I
I
I
I
I
I
A
3.0 ± 0.08
0.3 ± 0.1
0.5
I
1.8
C 0.3
0.22 ± 0.05
I
0.1 ± 0.05
I
3 = 1.5 ± 0.05
I
Battery life extension by automatic charge pump
switch between
×1, ×1.5
and
×2
according to the
detection of the LED drive current
Controlling 1 to 4 lights of white LED connected
in parallel
Set up LED drive current value by external resistor
(120k
Ω
: 20mA/ch)
1-wire input controlling
ON/OFF and brightness control by PWM signal
controlling of EN pin (10 to 100%)
Soft start circuit built-in
Thermal shut down circuit built-in
Input voltage range
No-load current (I
OUT
= 0mA): 2.7 to 4.6V
Load current (I
OUT
= 80mA): 3.0 to 4.6V
Maximum output voltage: 4.9V (typ)
Maximum output current: 80mA (typ)
Quiescent current
Not-switching (×1 mode): 0.3mA (typ)
Switching (×1.5 mode): 1.5mA (typ)
Switching (×2 mode): 1.5mA (typ)
Standby current: 0.01µA (typ)
Operating frequency: 1MHz (typ)
LED drive current accuracy between channel
(REST = 120k
Ω
): ± 5% (max)
Package: 16-pin QFN
PACKAGE DIMENSIONS
(Unit: mm)
TOP VIEW
3.0 ± 0.08
B
BOTTOM VIEW
1.8
0.02 S A B
S
0.2 S
φ
0.05 M
S A B
APPLICATIONS
I
I
I
I
I
I
I
I
0.2 ± 0.05
Cellular phone
PDA
Portable games
Handy terminal
Digital still camera
Digital video camera
LCD panel back light
White LED driving
0.05 S
0.5
ORDERING INFORMATION
Device
SM8135AB
Package
16-pin QFN
0.7 ± 0.05
SEIKO NPC CORPORATION —1
SM8135A
BLOCK DIAGRAM
C1M C1P C2M C2P
VIN
Charge pump
1/ 1.5/ 2
VOUT
Mode control
&
Output voltage control
&
Protection
Current
control
&
Current
detect
DIN1
DIN2
TSD
DIN3
DIN4
Control
logic
ISET
EN
NC
(open at any time)
GND
GND
PGND
PIN DESCRIPTION
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Name
C2M
PGND
C1P
C1M
VIN
GND
EN
ISET
DIN4
DIN3
NC
GND
DIN2
DIN1
VOUT
C2P
I/O
–
–
–
–
–
–
I
I
O
O
–
–
O
O
O
–
Description
Charge pump boost capacitor connection 2M
Charge pump ground
Charge pump boost capacitor connection 1P
Charge pump boost capacitor connection 1M
Supply voltage input
Ground
Enable/PWM dimming pulse input (High active)
LED drive current setting resistor connection
LED drive current control output 4
(
connect to ground when not used)
LED drive current control output 3
(
connect to ground when not used)
No connection (leave open circuit for normal operation)
Ground
LED drive current control output 2
(
connect to ground when not used)
LED drive current control output 1
(
connect to ground when not used)
LED drive voltage output
Charge pump boost capacitor connection 2P
SEIKO NPC CORPORATION —2
SM8135A
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 PCB.
Note. The device may suffer breakdown if any one of these parameter ratings is exceeded.
Symbol
V
IN
V
EN
V
DIN1 to 4
V
OUT
I
OUT
P
D
T
JMAX
T
stg
Rating
−0.3
to 5.5
–0.3 to V
IN
+ 0.3
–0.3 to V
IN
+ 0.3
5.5
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
= 80mA
Logic-level pin
2.7
3.3
0
−30
typ
3.6
3.6
−
−
max
4.6
4.6
V
IN
+85
V
V
V
°C
Unit
SEIKO NPC CORPORATION —3
SM8135A
Electrical Characteristics
V
IN
= 3.6V, GND = 0V, Ta = 25°C unless otherwise noted.
Rating
Parameter
Standby current
Pin
VIN
Symbol
I
STB
I
DD1
Quiescent current
VIN
I
DD2*1
I
DD3
Output voltage
Maximum output current
Operating frequency
Internal power-ON reset time
*1
Soft start time
LED drive pin leakage current
LED drive current
LED drive current matching
LED drive pin voltage
LED drive current
setting resistance
*1
EN hold time
*1
PWM input pulse frequency
*1
PWM input pulse duty
*1
Logic input voltage
VOUT
VOUT
C1M
EN
DIN1 to 4
DIN1 to 4
DIN1 to 4
DIN1 to 4
DIN1 to 4
ISET
EN
EN
EN
EN
V
OUT
I
OUT
f
OSC
T
POR
T
SS
I
Leak1 to 4
I
LED1 to 4
∆I
LED
V
DIN1 to 4
RSET
T
CEH
f
PWM
D
PWM
V
IH
V
IL
Logic input current
*1. Design guaranteed value
EN
I
IH
I
IL
×1.5/×2.0
mode
×1.5/×2.0
mode switching frequency
Rest time from when power is applied
EN startup
→
I
LED
rising edge
Standby mode, DIN pin = 4.9V
×1.0
mode
×1.0
mode,
relative accuracy between channels
at I
LED
maximum setting
×1.0
mode
RSET minimum value
Time from when EN = LOW until
shutdown
PWM dimming signal frequency
PWM dimming signal duty range
HIGH-level input voltage range
LOW-level input voltage range
Pull-down pin, EN pin = 3.6V
EN pin = 0V
Condition
min
Standby mode
×1.0
mode, I
OUT
= 0mA
×1.5
mode, I
OUT
= 0mA
×2.0
mode, I
OUT
= 0mA
–
–
–
–
4.4
80
750
–
0.70
–
18.0
–5.0
–
60
0.50
10
10
1.4
–
–
–1.0
typ
0.01
0.3
1.5
1.5
4.9
–
1000
0.05
1.43
0.01
20.0
–
200
–
1.00
–
–
–
–
5.0
–
max
1.00
1.0
4.5
4.5
5.4
–
1250
1.00
3.00
1.00
22.0
+5.0
–
–
1.50
100
100
–
0.3
10.0
–
µA
mA
mA
mA
V
mA
kHz
ms
ms
µA
mA
%
mV
kΩ
ms
kHz
%
V
V
µA
µA
Unit
SEIKO NPC CORPORATION —4
SM8135A
FUNCTIONAL DESCRIPTION
LED Drive Current Setting
The SM8135A LED drive current can be set using a combination of 2 methods: (1) current setting resistance
connected to ISET, and (2) PWM signal input control on the EN pin.
(1) Setting LED drive current using RSET
The LED drive maximum current value per LED (I
LED MAX
) is determined by the resistor (RSET) connected
to the ISET pin. The relationship between RSET and I
LED MAX
is given by the following equation.
I
LED MAX
[mA] = 2400/RSET [kΩ]
(For example, I
LED MAX
= 20mA when RSET = 120kΩ.)
The RSET resistance has a minimum rating of 60kΩ. At this value of resistance, the I
LED MAX
has a maximum
rating of 40mA/LED. However, note that the total LED drive current for all LEDs must not exceed 80mA.
50
ISET
I
LED MAX
[mA]
40
30
20
10
0
RSET
GND
0
100
200
300
400
500
RSET [kΩ]
RSET vs. I
LED MAX
SEIKO NPC CORPORATION —5
单片机
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