L9800 datasheet(32/55 Pages) STMICROELECTRONICS

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Four parameters can be set:

1. Duty cycle (bits PWM_LED_DC.DUTY_CYCLE)

8 bits are available to achieve 0.39% duty cycle resolution.

When the microcontroller programs a new duty cycle, the PWM LED generator waits until the previous cycle is

completed before using the new duty cycle (this happens also when the duty cycle is 100%) - the new duty

cycle is taken with the next PWM cycle, while the new duty cycle is immediately taken if the previous DC was

0%).

Maximum duty cycle achievable is 100% (PWM_LED_DC.DUTY_CYCLE set to “11111111B”)

2. Frequency (bits CFG_2.PWM_DIV_LED)

Using 2 bits it is possible to select the divider for fINT to achieve the needed duty cycle:

–

00B = PWM frequency is 122.5 Hz

–

01B = PWM frequency is 245.1 Hz

–

10B = PWM frequency is 490.2 Hz

–

11B = PWM frequency is 980.4 Hz

3. Mapping registers (PWM_SEL and PWM_MAP)

To correctly use the PWM LED generator:

•

Configure the channel output control and mapping register (PWM_SEL and PWM_MAP).

•

Write the duty cycle control register (PWM_LED_DC) to enable the PWM LED generation.

7.4

Electrical parameters

3 V < VBATT < 18 V, 3 V < VDDIO < 5.5 V, T J = -40 °C to 150 °C, unless otherwise noticed.

Table 14. Power stages electrical parameters

Symbol

Description

Test condition

Min.

Typ.

Max.

Unit

Power stage

RDS(ON)

On-state resistance

TJ = 25 °C

0.77

Ω

TJ = 150 °C, IL= 100 mA

1.7

Ω

IL(NOM)

Nominal load current (all channels active) TJ ≤ 150 °C, design info

260

500

IL(EAR)

Load current for maximum energy

dissipation–repetitive (all channels active)

TJ ≤ 150°C, design info

220

VLS_DS(CL) Drain to source output clamping voltage

IL = 10mA

IL(OFF)_LS

Output leakage current (each channel) TJ

= 150 °C

VBATT = 0 V, VDDIO = 0 V,

VSOURCE= 0 V, VDS = 28 V (with at

least another channel’s VDS= 29 V),

TJ up to 150°C

-4

µA

E AR

Maximum energy dissipation repetitive

pulses - 2*IL(EAR) (two channels in

parallel)

TJ(0) = 85 °C, IL(0) = 2*IL(EAR), 2*106

cycles

EAS

Maximum energy dissipation single pulse

T = 25 °C, IL = 2 * 200 mA

Maximum energy dissipation single pulse

T = 150 °C, IL = 400 mA

EAR

Maximum energy dissipation repetitive

pulses - IL(EAR)

T = 85 °C, 2*106 cycles

Timings

tDELAY(ON)

Turn-ON delay (from INn pin or bit to

VOUT = 90% VBATT)

RL = 50 Ω, VBATT = 14 V,

Active or limp-home mode

1.5

µs

tDELAY(OFF)

Turn-OFF delay (from INn pin or bit to

VOUT = 10% VBATT)

RL = 50 Ω, VBATT = 14 V,

Active or limp-home mode

2.5

µs

L9800

Power stages

DS14041 - Rev 2

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