50.7.2 LCD Voltage Regulator and LCD Output Buffers

The LCD Voltage Regulator is a complete solution to drive an LCD display. It integrates a low-power LDO regulator with programmable output voltage and buffers to drive the LCD lines. A capacitor is required at the LDO regulator output (VDDLCD). This regulator can be set in Active (Normal) mode, in Bypass mode (HiZ mode), or in OFF mode.

In Normal mode, the VDDLCD LDO regulator output can be selected from 2.4V to 3.5V using LCDVROUT bits in the Supply Controller Mode Register (SUPC_MR), with the conditions:
- VDDLCD ≤ VDD3V3 - 100 mV.
In Bypass mode (HiZ mode), the VDDLCD is set in high impedance (through the LCDMODE bits in SUPC_MR register), and can be forced externally. This mode can be used to save the LDO operating current.
In OFF mode, the VDDLCD output is pulled down.

Important: When using an external or the internal voltage regulator, VDD3V3 must be still supplied with the conditions: 2.4V≤ VDDLCD ≤ VDD3V3 and VDD3V3 ≥ 2.5V.

Table 50-18. LCD Voltage Regulator Characteristics
Symbol	Parameter	Conditions	Min	Max	Unit
V_VDD3V3	Input supply voltage range	–	2.5	3.6	V
V_DDLCD	Programmable output range	Refer to Table 50-19			V
V_ACC	V_DDLCD accuracy	With respect to programmed output range	-50	+50	mV
I_VDD3V3	Current consumption	–	–	7	μA
C_OUT	Output capacitor on VDDLCD⁽¹⁾	ESR for 1 μF capacitor ESR for 10 μF capacitor	1 5 1	10 20 10	μF mΩ mΩ
t_ON	Start-up time⁽¹⁾	C_OUT= 1 μF, VDDLCD max	–	2.5	ms

Note:

Simulation data.

Table 50-19. VDDLCD Voltage Selection at VDD3V3 = 3.6V
VROUT	0	1	2	3	4	5	6	7	8	9	10	11	12	13	12	13
V_DDLCD	2.375	2.45	2.525	2.60	2.675	2.75	2.825	2.90	2.975	3.05	3.125	3.20	3.275	3.35	3.425	3.50

Table 50-20. LCD Analog Buffers Bias Generation Characteristics
Symbol	Parameter	Conditions	Min	Max	Unit
I_DDIN	Current consumption (VDD3V3)	Buffered	–	52	μA
I_DDIN	Current consumption (VDD3V3)	Unbuffered	–	5	μA
Z_OUT	Buffer output impedance⁽¹⁾	Buffered	500	1300	Ω
Z_OUT	Buffer output impedance⁽¹⁾	Unbuffered	300k	1Meg	Ω
C_LOAD	Capacitive output load⁽¹⁾	–	10p	50n	F

Note:

Simulation data.