LTC3370 datasheet(21/44 Pages) LINER

21 / 44 page

LTC3372

Rev. A

For more information www.analog.com

Table 1. Master Slave Program Combinations (Each Letter

Corresponds to a Low Voltage Power Stage)

PROGRAM

CODE

C3C2C1

BUCK 1

BUCK 2

BUCK 3

BUCK 4

000

001

ABC

010

ABC

FGH

011

ABCH

100

ABC

Not Used

FGH

101

ABCD

Not Used

110

ABCD

Not Used

FGH

111

ABCD

Not Used

EFGH

Power Failure Reporting via RST Pin

Power failure conditions of all LV buck regulators are

reported by the single RST pin. Each LV regulator has an

internal power good signal. If LV Buck 1 output voltage

falls below 98%, or any of the Buck 2-4 outputs falls below

95%, of its programmed value, or if any LV regulator’s

output rises above 107.5% of its programmed value, its

internal power good signal is pulled low. If any internal

power good signal stays low for greater than 100μs, then

the RST pin is pulled low. The RST low signal indicates to

a microprocessor that a power failure fault has occurred.

The 100μs filter time prevents a false fault indication low

due to a output/load transient.

The internal power good comparators have hysteresis, so

the regulated output voltage of an enabled regulator has

to move back into the power good window by more than

the hysteresis for its power good signal to transition high.

Once all enabled LV regulator outputs are power good for

202ms (typical, CT = 10nF), the RST output goes high

impedance (pulled high by external resistor/current). If

all LV buck regulators are disabled, RST pulls low.

Temperature Monitoring and Overtemperature

Protection

To prevent thermal damage to the IC and its surrounding

components, the LV regulators have an overtemperature

(OT)function.Whenthe LTC3372dietemperaturereaches

170°C (typical) all LV buck switching regulators are shut

down and remain in shutdown until the die temperature

falls to 160°C (typical).

Thetemperaturemaybereadbackbytheuserbysampling

the TEMP pin analog voltage. The temperature, T, indicated

by the TEMP pin voltage is given by:

T =

VTEMP − 45mV

7mV

• 1°C

To reduce quiescent current (IQ), if all the LV buck regula-

tors are shut down, the temperature monitor also shuts

down and the TEMP pin becomes high impedance. The

temperature monitor can be disabled by tying the TEMP

pin to INTVCC to save IQ.

Programming the Operating Frequency

Selection of the operating frequency is a trade-off between

efficiency and component size. High frequency operation

allows the use of smaller inductor and capacitor values.

Operation at lower frequencies improves efficiency by

reducing internal gate charge losses but requires larger

inductance values and/or capacitance to maintain low

output voltage ripple.

The frequency of the internal oscillator (system clock)

is determined by an external resistor that is connected

between the RT pin and ground. The operating frequency

can be calculated using the following equation:

fOSC =

8 • 1011 • ΩHz

The oscillator is designed to function with operating fre-

quencies between 1MHz and 3MHz, it has safety clamps

that prevent the oscillator from running faster than 4MHz

(typical) or slower than 250kHz (typical). Tying the RT pin

to INTVCC sets the oscillator to the default internal operat-

ing frequency of 2MHz (typical).

The internal oscillator can be synchronized through an

internal PLL circuit to an external frequency by applying

a square wave clock signal to the PLL/MODE pin. During

synchronization, the top MOSFET turn-on of LV buck regu-

lator 1 is phase-locked to the rising edge of the external

frequency source. All other LV regulators are locked to

the appropriate phase of the external frequency source.

OPERATION

LTC3370 数据表(PDF) 21 Page - Linear Technology

LTC3370 数据表(HTML) 21 Page - Linear Technology

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 42 43 44

数据表下载

链接网址

LTC3370 数据表(PDF) 21 Page - Linear Technology

LTC3370 数据表(HTML) 21 Page - Linear Technology

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 42 43 44

数据表 下载

链接网址

数据表下载