Datasheet

SH1107
21
DC-DC Voltage Converter
It is a switching voltage generator circuit, designed for hand held applications. In SH1107, built-in DC-DC voltage converter
accompanied with an external application circuit (shown in Figure 12) can generate a high voltage supply VPP from a low
voltage supply input AVDD. VPP is the voltage supply to the OLED driver block
DC-DC
AVDD
(2.4~3.5)
C1
VSS
VBREF
VSS
VSS
VSS
L
D
Q
C2
C3
C4
C5
AVDD
(2.4~3.5)
R1
R2
R3
R4
Vpp
SENSE
FB
SW
Figure 12
VPP= (1+
2R
1R
) X VBREF, (R2: 80 - 120kΩ )
Note: R4&C5 are optional; they can increase the efficiency of inductance
Current Control and Voltage Control
This block is used to derive the incoming power sources into different levels of internal use voltage and current. VPP and VDD
are external power supplies. IREF is a reference current source for segment current drivers, it can change the brightness of the
screen and the value depends on the resistance of R
ref
and Vpp:
When Vpp=15V, contrast = 0xff, the value of resistor R
ref
can be found as Table 9:
Table 9
IREF
15.625µA 11.25µA 6.25µA
I
seg
(Max)
500µA 360µA 200µA
R
ref
750 KΩ 1MΩ 1.8MΩ
Common Drivers/Segment Drivers
Segment drivers deliver 128 current sources to drive OLED panel. The driving current can be adjusted up to 500µA with 256
steps. Common drivers generate voltage scanning pulses.