ZL1505

10

FN6845.3

February 25, 2011

ZL1505 Overview

Theory of Operation

The ZL1505 is a synchronous N-channel MOSFET driver that is

intended for use with Zilker Labs Digital-DC PWM controllers to

enable a high-efficiency DC/DC conversion scheme. The

patented Digital-DC control scheme utilizes a closed-loop

algorithm to optimize the dead-time applied between the gate

drive signals for the high-side and low-side MOSFETs. By

monitoring the duty cycle of the resulting DC/DC converter

circuit, this dynamic routine continuously varies the MOSFET

dead times to optimize conversion efficiency in response to

varying circuit conditions. The ZL1505’s dual PWM input

configuration enables this optimization scheme to be applied

while minimizing the complexity within the driver device. Please

refer to the ZL2004 data sheet for details on the dynamic

dead-time optimization routine.

The ZL1505 integrates two powerful gate drivers that have been

optimized for step-down DC/DC conversion circuit configurations

whose output current can exceed 40A per phase. The ZL1505

also integrates a 30V bootstrap Schottky diode to minimize the

external components and provide a high drive voltage to the

high-side driver device.

Variable Gate Drive Current

The ZL1505 incorporates an innovative variable drive current

scheme that enables the user to optimize the gate drive current

levels to the requirements of the external MOSFETs used over a

wide range of operating frequencies. Each of the gate drivers

incorporates a logic input (HSEL and LSEL) that allows the user to

select the gate drive strength to 50% or 100% of the total rated

drive current.

With the HSEL pin connected to the BST pin, the high-side driver

can deliver the full rated gate drive current; with the HSEL pin

connected to the SW pin, the output current will be limited to

50% of the full rated output capability. With the LSEL pin

connected to VDD, the low-side driver can deliver the full rated

gate drive current; with the LSEL pin connected to GND, the

+85°C, +25°C, and -25°C.

(Continued)

4.5

7.5

7.0

6.5

6.0

5.5

5.0

17.5

11.5

13.5

15.5

5.5

9.5

7.5

3.5

HSEL = SW

HSEL = BST

4.5

7.5

7.0

6.5

6.0

5.5

5.0

8.5

5.5

6.5

7.5

3.5

4.5

-25

°C

+25

°C

+85

°C

4.5

7.5

7.0

6.5

6.0

5.5

5.0

11.5

5.5

7.5

9.5

3.5

HSEL = SW

HSEL = BST

4.5

7.5

7.0

6.5

6.0

5.5

5.0

7.5

4.5

5.5

6.5

3.5

-25

°C

+25

°C

+85

°C