NT7502H-TABF1 Ver la hoja de datos (PDF) - Novatek Microelectronics
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NT7502H-TABF1 Datasheet PDF : 54 Pages
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NT7502
VSS
C1
VOUT
CAP3+
C1
CAP1-
C1
CAP1+
CAP2+
C1
CAP2-
4x step-up voltage circuit
VOUT = 4 X VDD2 = 12V
VDD2 = 3V
VSS = 0V
4x step-up voltage relationships
VSS
C1
VOUT
CAP3+
CAP1-
C1
CAP1+
CAP2+
C1
CAP2-
3x step-up voltage circuit
VOUT = 3 X VDD2 = 9V
VDD2 = 3V
VSS = 0V
3x step-up voltage relationships
VSS
C1
VOUT
CAP3+
CAP1-
C1
CAP1+
CAP2+
CAP2-
2x step-up voltage circuit
VOUT = 2 X VDD2 = 6V
VDD2 = 3V
VSS = 0V
2x step-up voltage relationships
Figure. 7
The Voltage Regulator Circuit
The step-up voltage generated at VOUT outputs the liquid
crystal driver voltage V0 through the voltage regulator circuit
Because the NT7502 chips have an internal high-accuracy
fixed voltage power supply with a 64-level electronic volume
function and internal resistors for the V0 voltage regulator,
systems can be constructed without having to include
high-accuracy voltage regulator circuit components.
Moreover, in the NT7502, three types of thermal gradients
have been prepared as VREG options: (1)
approximately –0.05%/℃ (2) approximately –0.2%/℃, and
(3) external input (supplied to the VEXT terminal).
When the V0 Voltage Regulator Internal Resistors Are
Used
Through the use of the V0 voltage regulator internal resistors
and the electronic volume function the liquid crystal power
supply voltage V0 can be controlled by commands alone
(without adding any external resistors), making it possible to
adjust the liquid crystal display brightness. The V0 voltage
can be calculated using equation A-1 over the range where
V0 < VOUT .
V0 = ( 1+Rb/Ra)*VEV = ( 1+Rb/Ra)* (1-(63-α)/162)*VREG (Equation A-1)
Ra
Vss
Rb
Vout
-
+
Vo
VEV
VEV (constant voltage
supply + electronic volume)
18
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