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MAX1980

Quick-PWM Slave Controller with Driver Disable for Multiphase DC-DC Converter

Maxim Integrated 

Quick-PWM Slave Controller with

Driver Disable for Multiphase DC-DC Converter

Pin Description (continued)

PIN

NAME

DESCRIPTION

17

V+

Battery Voltage Sense Connection. Connect V+ to the input power source. V+ is used only for PWM one-

shot timing (see the On-Time Control and Active Current Balancing section).

Open-Drain Current-Limit Output. Connect to the master controller’s adjustable current-limit input (ILIM)

18

LIMIT

according to the Standard Application Circuit (Figure 1). When the voltage across the master controller’s

current-sense resistor (VCM+ - VCM-) exceeds the current-limit threshold (VILIM/10), the MAX1980 pulls

LIMIT low.

Dual-Mode Current-Limit Adjustment and Standby Input. The current-limit threshold voltage is 1/10 the

19

ILIM

voltage seen at ILIM (VILIM) over a 400mV to 1.5V range. If VILIM drops below 250mV, the slave

controller enters a low-power standby mode, forcing DL low and DH low.

Trigger Input. Connect to the master controller’s low-side gate driver. The trigger input’s polarity is pin

20

TRIG selectable: POL = VCC or floating triggers on the rising edge (out-of-phase operation), and POL = GND

triggers on the falling edge (in-phase operation).

Table 1. Component Selection for Standard

Applications

COMPONENT

Output Voltage

Input Voltage Range

Maximum Load Current

Inductor (each phase)

Frequency

High-Side MOSFET

(NH, each phase)

Low-Side MOSFET

(NL, each phase)

Input Capacitor (CIN)

Output Capacitor (COUT)

Current-Sense Resistors

(RCS and RCM)

Voltage Positioning Gain

(AVPS)

CIRCUIT OF FIGURE 1

0.6V to 1.75V

7V to 24V

40A

0.6µH

Sumida CDEP134H-0R6 or

Panasonic ETQP6F0R6BFA

300kHz (TON = float)

International Rectifier

(2) IRF7811W

International Rectifier

(2) IRF7822 or

Fairchild (3) FDS7764A or

(6) 10µF, 25V

Taiyo Yuden

TMK432BJ106KM or

TDK C4532X5R1E106M

(8) 270µF, 2.0V

Panasonic EEFUE0E271R

1.5mΩ

1

Detailed Description

The MAX1980 step-down slave controller is intended for

low-voltage, high-current, multiphase DC-DC applica-

tions. The MAX1980 slave controller can be combined

with any of Maxim’s Quick-PWM step-down controllers to

form a multiphase DC-DC converter. When compared to

single-phase operation, multiphase conversion lowers the

peak inductor current by distributing the load current

between parallel power paths. This simplifies component

selection, power distribution to the load, and thermal lay-

out. Existing Quick-PWM controllers, such as the

MAX1718, function as the master controller, providing

accurate output-voltage regulation, fast transient

response, and multiple fault-protection features.

Synchronized to the master’s low-side gate driver, the

MAX1980 includes a constant on-time controller, syn-

chronous rectifier gate drive, active current balancing,

and precision current-limit circuitry.

On-Time Control and Active

Current Balancing

The MAX1980 slave controller uses a constant on-time,

voltage feed-forward architecture similar to Maxim’s

Quick-PWM controllers (Figure 2). The control algorithm

is simple: the high-side switch on-time is determined

solely by a one-shot whose period is inversely propor-

tional to input voltage and directly proportional to the

compensation voltage (VCOMP). Another one-shot sets a

minimum off-time (130ns typical). The on-time one-shot

is triggered when the following conditions are satisfied:

The slave detects a transition on the TRIG input, the

slave controller’s inductor current is below its current-

limit threshold, and the minimum off time has expired.

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