CS1615/16

2

DS961F1

1. INTRODUCTION

Figure 1. CS1615/16 Block Diagram

A typical schematic using the CS1615/16 IC is shown on the

previous page.

Startup current is provided from a patent-pending, external, high-

voltage source-follower network. In addition to providing startup

current, this unique topology is integral in providing compatibility

to the IC. During normal operation, an auxiliary winding on the

flyback transformer or buck-boost inductor back-biases the

source-follower circuit and provides steady-state operating

current to the IC to improve system efficiency.

and is used to control the adaptive dimmer-compatibility

algorithm and to extract the phase of the input voltage for output

dimming control. The SOURCE pin is used to provide a control

signal for the high-voltage source-follower circuit during Leading-

edge Mode and Trailing-edge Mode; it also provides the current

during startup.

The digital dual-mode controller is implemented with peak-

current mode primary-side regulation, which eliminates the need

for additional components to provide feedback from the

secondary and reduces system cost and complexity. Voltage

across a user-selected resistor is sensed through pin FBSENSE

to control the peak current of the primary-side inductor. Leading-

edge and trailing-edge blanking on pin FBSENSE prevents false

triggering. The required target LED current and average flyback

transformer and buck-boost inductor input current are set by

CTRL2, respectively. The controller ensures half line-cycle

averaged constant output current.

Pin FBAUX is used for zero-current detection to ensure

quasi-resonant switching of the single stage output. When an

external negative temperature coefficient (NTC) thermistor is

connected to pin eOTP, the CS1615/16 monitors the system

temperature, allowing the controller to reduce the output current

of the system. If the temperature reaches a designated high set

point, the IC is shut down and stops switching.

2

IAC

SGND

15k

ADC

11

FBSENSE

+

-

DAC

+

-

Peak

Control

12

GND

OLP

+

-

OCP

Blank

3

CLAMP

+

-

MUX

9

+

-

V

CONNE CT(th)

10

CTRL2

8

CTRL1

eOTP

FBAUX

16

+

-

Zero-current

Detect

+

-

Output

Overvoltage

14

VDD

+

-

Voltage

Regulator

V

Z

POR

13

GD

VDD

VDD

VDD

4

+

-

V

FS TA RT(th )

3