SSM3515CCBZ-R7 datasheet(26/41 Pages) AD

26 / 41 page

SSM3515

Data Sheet

Rev. A| Page 26 of 41

The VBAT_INF point is defined as the battery voltage at which

the limiter either activates or deactivates depending on the

LIM_EN mode (see Table 19). When the battery voltage is

greater than VBAT_INF, the limiter is not active. When it

battery voltage is less than VBAT_INF, the limiter is activated.

The VBAT_INF bits can be set from 3.8 V to 16.2 V. The 8-bit

value for the voltage can be calculated using the following

equation.

Voltage = 3.8 + 12.4 × Decimal Value/255

Convert the decimal value to an 8-bit hex value and use it to set

the VBAT_INF bits.

The rate at which the limiter threshold is lowered relative to

the amount change in VBAT below the VBAT_INF point is

determined by the slope bits (Register 0x08, Bits[1:0]).

The slope is the ratio of the limiter threshold reduction to the

VBAT voltage reduction.

Slope = ΔLimiter Threshold/ΔVBAT

The slope ratio can be set from 1:1 to 4:1. This function is useful

to prevent early shutdown under low battery conditions. As the

VBAT voltage falls, the limiter threshold is lowered. This results in

the lower output level and therefore helps to reduce the current

drawn from the battery and in turn helps prevent early shutdown

due to low VBAT.

The limiter offers various active modes which can be set using the

LIM_EN bits (Register 0x07, Bits[1:0]) and the VBAT_TRACK bit,

as shown in Table 19.

When LIM_EN = 01, the limiter is enabled. When LIM_EN = 10,

the limiter mutes the output if VBAT falls below VBAT_INF. When

LIM_EN = 11, the limiter engages only when the battery voltage

is lower than VBAT_INF. When VBAT is above VBAT_INF, no

limiting occurs. Note that there is hysteresis on VBAT_INF for the

limiter disengaging.

The limiter, when active, reduces the gain of the amplifier. The rate

of gain reduction or attack rate is determined by the LIM_ATR bits

(Register 0x07, Bits[5:4]). Similarly, when the signal level drops

below the limiter threshold, the gain is restored. The gain release

rate is determined by the LIM_RRT bits (Register 0x07, Bits[7:6]).

INPUT LEVEL

AMPLIFIER CLIPPING LEVEL

LIM_EN = 00

VBAT_TRACK = 0

Figure 67. Limiter Example (LIM_EN = 0b0, VBAT_TRACK = 0bx)

VBAT

LIM_THRES

LIMITER THRESHOLD FIXED AT SET VALUE

AND DOES NOT TRACK VBAT

Figure 68. Limiter Fixed (LIM_EN = 0b01, VBAT_TRACK = 0b0)

Table 19. Limiter Modes

LIM_EN

VBAT_TRACK

Limiter

VBAT < VBAT_INF

VBAT > VBAT_INF

Comments

0/1

Not applicable

See Figure 67

Fixed

Use the set threshold

See Figure 68

Variable

Lowers the threshold

Use the set threshold

See Figure 69 and Figure 70

0/1

Fixed

Mutes the output

Use the set threshold

Fixed

Use the set threshold

No limiting

See Figure 71 and Figure 72

Variable

Lowers the threshold

No limiting

See Figure 73 and Figure 74

SSM3515CCBZ-R7 数据表(PDF) 26 Page - Analog Devices

SSM3515CCBZ-R7 数据表(HTML) 26 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

数据表下载

链接网址

SSM3515CCBZ-R7 数据表(PDF) 26 Page - Analog Devices

SSM3515CCBZ-R7 数据表(HTML) 26 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

数据表 下载

链接网址

数据表下载