MAX8743(2004) Просмотр технического описания (PDF) - Maxim Integrated

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MAX8743
(Rev.:2004)

Dual, High-Efficiency, Step-Down Controller with High Impedance in Shutdown

Maxim Integrated 

Dual, High-Efficiency, Step-Down

Controller with High Impedance in Shutdown

PIN

QSOP TQFN

7

3

8

4

9

5

10

7

11

8

12

11

13

12

14

13

15

14

16

15

17

16

18

18

19

19

20

20

21

21

22

22

23

—

Pin Description (continued)

NAME

FUNCTION

PGOOD

OVP

UVP

REF

ON1

ON2

ILIM2

FB2

OUT2

CS2

LX2

DH2

BST2

DL2

VDD

VCC

GND

Power-Good Open-Drain Output. PGOOD is low when either output voltage is more than 10%

above or below the normal regulation point, and during the 1.7ms soft-start time.

Overvoltage Protection Threshold. An overvoltage fault occurs if the voltage on FB1 or FB2 is

greater than the programmed overvoltage trip threshold. Adjustment range is 1V (100%) to 1.8V

(180%). Connect OVP to GND to set the default overvoltage threshold of 114% of nominal.

Connect to VCC to disable OVP and clear the OVP latch.

Undervoltage Protection Threshold. An undervoltage fault occurs if the voltage on FB1 or FB2 is less

than the undervoltage trip threshold (70% of nominal). Connect UVP to VCC to enable undervoltage

protection. Connect to GND to disable undervoltage protection and clear the UVP latch.

+2.0V Reference Voltage Output. Bypass to GND with 0.22µF (min) capacitor. Can supply 50µA

for external loads.

OUT1 ON/OFF Control Input. Connect to AGND to turn OUT1 off. Connect to VCC to turn OUT1 on.

OUT2 ON/OFF Control Input. Connect to AGND to turn OUT2 off. Connect to VCC to turn OUT2 on.

Current-Limit Threshold Adjustment for OUT2. The current-limit threshold at CS2 is 0.1 times the

voltage at ILIM2. Connect a resistor-divider network from REF to set the current-limit threshold

between 25mV and 250mV (with 0.25V to 2.5V at ILIM). Connect to VCC to assert 50mV default

current-limit threshold.

Feedback Input for OUT2. Connect to GND for 2.5V fixed output, or connect to a resistor-divider

network from OUT2 for an adjustable output between 1V and 5.5V.

Output Voltage Connection for the OUT2 PWM. Connect directly to the junction of the external

inductor and output filter capacitors. OUT2 senses the output voltage to determine the on-time

and also serves as the feedback input in fixed-output modes.

Current-Sense Input for OUT2. CS2 is the input to the current-limiting circuitry for valley current

limiting. For lowest cost and highest efficiency, connect to LX2. For highest accuracy, use a sense

resistor. See the Current-Limit Circuit (ILIM_) section.

External Inductor Connection for OUT2. Connect to the switched side of the inductor. LX2 serves

as the internal lower supply voltage rail for the DH2 high-side gate driver.

High-Side Gate-Driver Output for OUT2. Swings from LX2 to BST2.

Boost Flying Capacitor Connection for OUT2. Connect to an external capacitor and diode

according to the standard application circuit in Figure 1. See the MOSFET Gate Drivers (DH_,

DL_) section.

Low-Side Gate-Driver Output for OUT2. DL2 swings from PGND to VDD.

Supply Input for the DL Gate Drivers. Connect to system supply voltage, +4.5V to +5.5V. Bypass

to PGND with a low-ESR 4.7µF capacitor.

Analog Supply Input. Connect to system supply voltage, +4.5V to +5.5V, with a 20Ω series

resistor. Bypass to AGND with a 1µF capacitor.

Ground. Combined analog and power ground. Serves as negative input for CS_ amplifiers.

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