Package Lead Description
LEAD SYMBOL
PACKAGE LEAD #
24 Lead SO Wide
FUNCTION
1
VIN
Supply Voltage.
No connection.
2, 3
NC
4
VSW
Collector of NPN power switch for switching regulator section.
Connected to the heat removing leads.
5,6,7,8,17,18,19,20
Gnd
VFB1
VFB2
SELECT
9
Feedback input voltage 1 (referenced to 1.25V)
10
11
Feedback input voltage 2 (referenced to 1.25V)
Logic level input that selects either VFB1 or VFB2. An open selects
VFB2. Connect to Gnd to select VFB1
.
12
13
COMP
COSC
Output of the transconductance error amplifier.
A capacitor connected to Gnd sets the switching frequency.
Refer to Figure 1d.
14
15
WDI
Watchdog input. Active on falling edge.
CDelay
A capacitor connected to Gnd sets the Power On Reset and
Watchdog time.
RESET
IBIAS
RESET
output. Active low if VLIN is below the regulation limit.
If watchdog timeout is reached, a reset pulse train is issued.
16
21
A resistor connected to Gnd sets internal bias currents as well as
the COSC and CDelay charge currents.
22
23
VLIN
VREG
Regulated 5V output from the linear regulator section.
Input voltage to the linear regulator and the internal supply cir-
cuitry.
ENABLE
24
Logic level input to shut down the switching regulator.
Typical Performance Characteristics
4.5mA
0A
-10mA
-20mA
4.0mA
-30mA
-40mA
3.5mA
0A
20mA
40mA
60mA
80mA
100mA
0A
0.5A
1.0A
1.5A
2.0A
I
SW
I
LIN
Figure 1a. 5V Regulator Bias Current vs. Load Current.
Figure 1b. Supply Current vs. Switch Current.
180
160
1.4V
1.2V
1.0V
140
120
100
80
0.8V
0.6V
60
40
20
0.4V
0.2V
0.0V
0
0
500
1000
1500
2000
2500
3000
0A
0.5A
1.0A
SW
1.5A
2.0A
C
(pF)
OSC
I
Figure 1d. Oscillator Frequency (kHz) vs. COSC (pF), assuming RBIAS
64.9kΩ.
=
Figure 1c. Switch Saturation Voltage.
4
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
