4 monitoring voltage on the vp pin—vpmon, 5 data transmission out of the cs35l32, 6 error conditions – Cirrus Logic CS35L32 User Manual

Page 21: 9 led driver, Section 4.8.4, Section 4.9, Led driver, Cs35l32

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4.9 LED Driver

4.8.4

Monitoring Voltage on the VP Pin—VPMON

Monitoring of the voltage present on the VP pin is integrated internally to the CS35L32. The operating specifications for
this ADC path are given in

Table 3-7

. To determine the voltage present on VP, the following equation must be used:

OUT

is the digital output word (see

VPMON

p. 38

) in signed decimal format (–128 to +127), and VA is the voltage on the

VA pin. If VA = 1.8 V, VPMON can report values from 2.8 V (D

OUT

= –77 decimal) to 5.52 V (D

OUT

= 0 decimal).

4.8.5

Data Transmission out of the CS35L32

The ADSP, described in

Section 4.11

, can transmit all signals monitored in the CS35L32 to the system processor. The

data is presented on these outputs simultaneously.

4.8.6

Error Conditions

The CS35L32 monitors each monitoring ADC for overflow conditions.

Table 4-4

lists signal monitoring error conditions and

provides links to their associated register field descriptions.

If an overflow occurs, the appropriate xMON_OVFL bit is set, and, if the respective mask bit is cleared, an interrupt occurs.
Exiting the error occurs when the signal is no longer overflowing. No release bit needs to be toggled.

• Overflow for VPMON and VMON signals. Due to the analog prescaling applied to the analog input signals, which

are sampled to make the VPMON and VMON signals, overflow conditions are unlikely on these ADCs. This is
because the operating specifications for maximum and minimum voltage constrain the voltage on these pins to a
level far below that required to make the ADC overflow.
For VPMON, because a spurious overflow error can occur when the block is taken out of power down, it is advised
to read the error status registers after PDN_xMON has been cleared to clear the spurious error status bit.

• Overflow for the IMON signal. As

(see

) control allows the

greatest possible sample resolution over a wide range of output currents and sense resistors. If IMON_SCALE is
set too low for either the output current being monitored or the sense resistor being used, overflow of this ADC can
occur. When this error occurs, increasing the IMON_SCALE value can prevent the sampled signal from overflowing.

4.9 LED Driver

The CS35L32 includes a high-current flash LED driver (see

Fig. 4-6

), featuring two channels, FLOUT1 and FLOUT2, and

a boost converter and current regulator designed to power LEDs with up to 0.75 A per channel. Both channels can be
combined to drive an LED with 1.5 A by tying FLOUT1 and FLOUT2 together.

Figure 4-6. LED Driver Block Diagram

Table 4-4. Signal Monitoring Error Status Conditions

Error

Cross-Reference to Description

xMON overflow. Indicates the overrange
status in the VMON, IMON, or VPMON
ADC signal paths.

VMON_OVFL p. 42
IMON_OVFL p. 42
VPMON_OVFL p. 42

DOUT 128





255

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