SM8150A

SEIKO NPC CORPORATION —7

11-2. White LED Driver

Charge Pump Operating Mode Switching

The SM8150A switches between 3 charge pump operating modes;

×1 mode (VIN through mode), ×1.5 mode

(

×1.5 charge pump boost), and ×2 mode (×2 charge pump boost), reducing the total power dissipation. These

selecting occurs automatically in internal circuits, and cannot be controlled by external signals. If the LED

current drops below the setting value while operating in

×1 or ×1.5 mode, each LED drive circuit detects the

undercurrent and the operating mode is automatically selected

×1 → ×1.5, ×1.5 → ×2. This occurs even if only

one LED undercurrent condition is detected among the 7-channel LED drive circuits, thus it is recommended

that LED has small VF variation to optimize the total efficiency. In

×1.5 or ×2 mode operating, the SM8150A

generates "a mode reset signal" internally once every 1 second. This signal forces to select the mode

×1.5 →

×1, ×2 → ×1.5.

Reference Data

Parameter

Pin

Symbol

Condition

Rating

Unit

min

typ

max

*1. LDOUT1 to 2 and the DC/DC converter is disabled.

VIN

×1 mode, no load

–

0.3

1

mA

–

4

8

mA

×2 mode, no load

–

5

10

mA

*2. Over voltage protection threshold.

VOUT

Boost ON, no load

4.6

4.9

5.2

V

Output current

Boost ON

–

–

450

mA

Charge pump frequency

C1M

0.85

1.0

1.15

MHz

*3. The time from when one of the DIN1 to 7 outputs is enabled until the LED turns ON.

DIN1 to 7

–13

ms

LED drive pin leakage current

–

0.01

1.0

µA

LED current (max) 1

DIN1 to 6

23.5

25.0

26.5

mA

LED current relative accuracy

–3.0

–

+3.0

%

LED current (max) 2

DIN7

280

300

320

mA

Current consumption (No load)

0

1

2

3

4

5

6

7

2.7

3

3.3

3.6

3.9

4.2

4.5

VIN [V]

×1

×2

×1.5

Efficiency (DIN1 to 6: 25mA, DIN7: 155mA)

0

20

40

60

80

100

3.0

3.3

3.6

3.9

4.2

4.5

VIN [V]