CS1680

DS1055F1

3

2. PIN DESCRIPTION

Pin Name

Pin #

I/O

Description

CTRL2

1IN

Peak Current — Connect a resistor to this pin to set

the comparator threshold to

reflect the desired boost peak current in Trailing Edge Electronic Trans-

former Mode (Mode 2).

eOTP

2IN

External Overtemperature Protection — Connect an external NTC thermistor to

this pin, allowing the internal A/D converter to sample the change to NTC resistance.

BSTSENSE

3IN

Boost Stage Current Sense — The current flowing in the boost stage FET is

sensed across a resistor. The resulting voltage is applied to this pin and digitized for

use by the boost stage computational logic to determine the FET duty cycle.

GND

4PWR

Ground — Common reference. Current return for both the input signal portion of the

IC and the gate driver.

BSTGD

5OUT

Boost Gate Driver — Gate drive for the boost stage power FET.

VDD

6PWR

IC Supply Voltage — Connect a storage capacitor to this pin to serve as a reservoir for

operating current for the device, including the gate drive current to the power transistor.

GPIO

7IN/OUT

General Purpose Input/Output — Used to drive the FET gate for the startup circuit.

NC

8IN

No Connect — Leave pin not connected.

BUCKZCD

9IN

Buck Stage Zero-current Detect — Buck stage inductor sensing input. The pin is

connected to the drain of the buck stage power FET with a capacitor.

NC

10

IN

No Connect — Leave pin not connected.

CLAMP

11

OUT

Voltage Clamp Current Source — Connect to a voltage clamp circuit on the output

of the boost stage.

BUCKGD

12

OUT

Buck Gate Driver — Gate drive for the buck stage power FET.

BUCKSENSE

13

IN

Buck Stage Current Sense — The current flowing in the buck stage FET is sensed

across a resistor. The resulting voltage is applied to this pin and digitized for use by

the buck stage computational logic to determine the FET duty cycle.

VAC

14

IN

Rectifier Voltage Sense — A current proportional to the rectified line voltage is fed

into this pin. The current is measured with an A/D converter.

BSTOUT

15

IN

Boost Output Voltage Sense — A current proportional to the boost output is fed

into this pin. The current is measured with an A/D converter.

CTRL1

16

IN

Boost Stage Constant — Connect a resistor to this pin to set the constant ratio for

the boost stage current calculations in Leading Edge Electronic Transformer Mode

(Mode 3).

General Purpose Input/Output

Boost Gate Driver

Ground

Peak Current

External Overtemperature Protection

No Connect

GPIO

VDD

IC Supply Voltage

BSTGD

GND

CTRL2

NC

CLAMP

BUCKGD

BUCKSENSE

VAC

BSTOUT

CTRL1

eOTP

BSTSENSE

Boost Stage Current Sense

16-lead TSSOP

NC

BUCKZCD

7

6

5

4

3

2

1

10

11

12

13

14

15

16

8

9

No Connect

Voltage Clamp Current Source

Buck Gate Driver

Buck Stage Current Sense

Rectifier Voltage Sense

Boost Output Voltage Sense

Boost Stage Constant

Buck Stage Zero-current Detect

Figure 2. CS1680 Pin Assignments