
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
xternal Overtemperature Protection
No Connect
GPIO
VDDIC Supply Voltage
BSTGD
GND
CTRL2
NC
CLAMP
BUCKGD
BUCKSENSE
VAC
BSTOUT
CTRL1
eOTP
BSTSENSEBoost Stage Current Sense
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
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