NCP1508 Datasheet, PDF (2/15 Pages) ON Semiconductor – Up to 500 mA, 1 MHz, High Efficiency Synchronous Step−Down DC−DC Converter in DFN Package

NCP1508
COMPENSATION
RAMP
6
FB
GNDA ¹
CB0 ⁷
CB1 ⁸
SELECT
LOGIC
ISENS
SENFET
5
4
VCCA
VCCP
−
−
CMP
OA
+
+
−
CMP
+
PWM
OVP
PM
ILIM
+
CMP
−
−
CMP
+
CONTROL
BLOCK
(PWM,PM)
ISENS
DVR
DAMPING
Q1
3 _LX
SWITCHING
CONTROL
ZCL
−
CMP
+
6
FB
Q2
DVR
9
SHD
BANDGAP
REFERENCE
AND SOFT
START
ENABLE
DETECT
THERMAL
SHUTDOWN
MODE SELECTION
SYNC DETECT
AND
TIMING BLOCK
2
GNDP
10
SYNC
Figure 3. Simplified Block Diagram
PIN FUNCTION DESCRIPTION
Pin No.
Symbol
Type
1
GNDA
Analog Ground
2
GNDP
Power Ground
3
LX
Analog Output
4
VCCP
Analog Input
5
VCC
Analog Input
6
FB
Analog Input
7
CB0
Analog Input
8
CB1
Analog Input
9
SHD
Analog Input
10
SYNC
Analog Input
Description
Ground connection for the Analog Section of the IC. This is the GND for the FB,
REF, SYNC, CB, and SHD pins.
Ground Connection for the N−FET Power Stage.
Connection from Power Pass Elements to the Inductor.
Power Supply Input for the Switching P−FET.
Power Supply Input for Power and Analog V_CC.
Feedback Voltage from the Output of the Power Supply.
Selects V_out. This pin contains an internal pulldown resistor.
Selects V_out. This pin contains an internal pullup resistor.
Enable for Switching Regulator. This pin is Active High to enable the NCP1508.
The SHD Pin has an internal pulldown resistor to force the converter off if this pin
is not connected to the external circuit.
Synchronization input for the PWM converter. If a clock signal is present, the
converter uses the rising edge for the turn on. If this pin is low, the converter is in
the Pulsed mode. If this pin is high, the converter uses the internal oscillator for
the PWM mode. This pin contains an internal pulldown resistor.
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