ST7637 datasheet(59/210 Pages) SITRONIX

59 / 210 page

ST7637

Ver 1.6

59/210

2009/03

7.10.1.3. V0 fine tuning

ST7637 has 2 commands for fine tuning V0. These commands are VopOfsetInc (see section 9.1.47) and

VopOfsetDec (see section 9.1.48). When writing VopOfsetInc into IC for each time, V0 would increase 40mV; when writing

VopOfsetDec into IC for each time, V0 would decrease 40mV.

Example:

Vop[8:0]=011010010

EV[6:0]=0111111

VopOfsetInc x2

→ V0=3.6 + { 210 + (63-63) } x 0.04 + 0.04x2 =12.08 (V)

7.10.2. Voltage Follower Circuits

There is a build-in voltage follower circuits in ST7637 for generating Vg and Vm. These voltages are decided by bias

ratio selection circuitry which is set by users with software to control 1/5 to 1/12 bias ratios to match the optimum display

performance of LCD panel. Bias driving rule is listed below:

LCD bias

1/N bias

(2/N) x V0

(1/N) x V0

N=5 to 12

7.10.3. OTP Setting Flow

ST7637 provides the Write and Read function to write the electronic control value and built-in resistance

ratio into built-in OTP, and then read them from it. Using the Write and Read functions, you can store these

values appropriate to each LCD panel. This function is very convenient for user in setting from some different

panel’s voltage. But using this function must attention the setting procedure. Please see the following diagram.

Figure 7.10-5

V0 value control for different modules by loading Vop offset

Note1: This setting flow is used for LCM assembler.

Note2: OTP shouldn’t be written without preceding loading correctly from OTP in order to avoid some errors

during IC operation.

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