1021
SAM4CP [DATASHEET]
43051E–ATPL–08/14
45.5.3 Automatic Power Switch
45.5.4 LCD Voltage Regulator and LCD Output Buffers
The LCD Voltage Regulator is a complete solution to drive a LCD display. It integrates a low-power LDO regulator with
programmable output voltage and some buffers to drive the LCD lines. A 1
μ
F capacitor is required at the LDO regulator
output (VDDLCD). This regulator can be either set in active (normal) mode, or 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
VDDIO and,
VDDLCD
VDDIN - 150mV.
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 (4
μ
A).
In OFF mode, the VDDLCD Output is pulled down.
IMPORTANT: When using an external or the internal voltage regulator, VDDIO and VDDIN must be still supplied with the
conditions: 2.4V
VDDLCD
VDDIO/VDDIN and VDDIO/VDDIN
≥
2.5V.
Table 45-12. Automatic Power Switch Characteristics
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
V
IT+
V
IT-
V
IT_HYS
Positive-going input threshold voltage (VDDIO)
1.9
—
2.2
V
Negative-going input threshold voltage (VDDIO)
1.8
—
2.1
V
Threshold Hysteresis
—
100
—
mV
Table 45-13. LCD Voltage Regulator Characteristics
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
V
VDDIN
Supply Voltage Range (VDDIN)
2.5
—
3.6
V
V
VDDLCD
Programmable Output Range
See
Table 45-14
.
2.4
—
3.5
V
Output voltage Accuracy
-10
—
10
%
I
VDDIN
d
VOUT
/ d
VDDIN
Current Consumption (VDDIN)
LDO Enabled
—
—
4
μ
A
VDDLCD variation with VDDIN
—
-50
-70
mV/V
I
LOAD
Output Current
DC or transient load averaged by
the external decoupling capacitor
—
—
2
mA
C
OUT
t
ON
Output Capacitor on VDDLCD
1
—
10
μ
F
Startup Time
C
OUT
= 1
μ
F
—
—
1
ms
Table 45-14. VDDLCD Voltage Selection at VDDIN = 3.6V
LCD
VROUT
VDDLCD
(V)
LCD
VROUT
VDDLCD
(V)
LCD
VROUT
VDDLCD
(V)
LCD
VROUT
VDDLCD
(V)
0
2.86
4
2.57
8
3.45
12
3.16
1
2.79
5
2.50
9
3.38
13
3.09
2
2.72
6
2.43
10
3.31
14
3.02
3
2.64
7
2.36
11
3.23
15
2.95