Package Lead Description
FUNCTION
PACKAGE LEAD #
16 Lead SO Wide
1
LEAD SYMBOL
SYNC
A pulse train on this lead will synchronize the oscillator. Sync threshold level
is 2.4V. Synchronization frequency should be at least 10% higher than the reg-
ular operating frequency. The sync feature is level sensitive.
2
3
4
CT
RT
The oscillator integrating capacitor is connected to this lead.
The oscillator charge current setting resistor is connected to this lead.
VFB1
The inverting input of the channel 1 error amplifier is brought out to this lead.
The lead is connected to a resistor divider which provides a measure of the
output voltage. The input is compared to a 1.275V reference, and channel 1
2ª
error amp output is used as the V
PWM control voltage.
5
6
7
COMP1
VFFB1
Channel 1 error amp output and PWM comparator input.
This lead connects to the non-inverting input of the channel 1 PWM comparator.
GATE1
This lead is the gate driver for the channel 1 FET. It is capable of providing
nearly 1A of peak current.
8
9
LGND
PGND
GATE2
This lead provides a ÒquietÓ ground for low power circuitry in the IC. This
lead should be shorted to the PGND lead as close as possible to the IC for best
operating results.
This lead is the power ground. It provides the return path for the FET gate dis-
charge. It should be shorted to the LGND lead as close as possible to the IC for
best operating results.
10
This lead is the gate driver for the channel 2 FET. See GATE1 lead description
for more details.
11
12
13
14
VFFB2
COMP2
VFB2
This lead connects to the non-inverting input of the channel 2 PWM comparator.
Channel 2 error amp output and PWM comparator input.
Inverting input for the channel 2 error amp. See VFBI for more details.
ENABLE
The regulator controlled by channel 2 may be turned on and off selectively by
the user. Pulling the ENABLE lead above 3.5V will turn channel 2 on. Setting
the ENABLE lead voltage below 1.5V guarantees that channel 2 is off.
15
16
VREF
This lead is the output of a ± 3% reference. This reference drives most of the
on-chip circuitry, but will provide a minimum of 10 mA to external circuitry if
needed. The reference is inherently stable and does not require a compensa-
tion capacitor, but use of a decoupling capacitor will reduce noise in the IC.
VIN
This lead is the power supply input to the IC. The maximum input voltage
that can be withstood without damage to the IC is 20V.
4
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
