5 Pin Configuration and Functions

Figure 5-1 LM25088-1 16-PinPWP Package (Dither Version)(Top View)

Figure 5-2 LM25088-2 16-PinPWP Package (Restart Version)(Top View)

Table 5-1 Pin Functions

PIN		DESCRIPTION	APPLICATION INFORMATION
NUMBER	NAME	DESCRIPTION	APPLICATION INFORMATION
1	VIN	Input supply voltage	IC supply voltage. The operating range is 4.5 V to 42 V.
2	EN	Enable input	If the EN pin voltage is below 0.4 V, the regulator is in a low power state. If the EN pin voltage is between 0.4 V and 1.2 V, the controller is in standby mode. If the EN pin voltage is above 1.2 V, the controller is operational. An external voltage divider can be used to set a line undervoltage shutdown threshold. If the EN pin is left open, a 5-µA pullup current forces the pin to the high state and enables the controller.
3	SS	Soft-start	When SS is below the internal 1.2-V reference, the SS voltage controls the error amplifier. An internal 11-µA current source charges an external capacitor to set the start-up rate of the controller. The SS pin is held low in the standby, VCC UV, and thermal shutdown states. The SS pin can be used for voltage tracking by connecting this pin to a controller voltage supply less than 1.2 V. The applied voltage acts as the reference for the error amplifier.
4	RAMP	Ramp control signal	An external capacitor connected between this pin and the GND pin sets the ramp slope used for emulated current mode control. The recommended capacitor range is 100 pF to 2000 pF. See the Application and Implementation section for a selection of capacitor values.
5	RT/SYNC	Internal oscillator frequency set input and synchronization input	The internal oscillator is programmed with a single resistor between this pin and the GND pin. The recommended frequency range is 50 kHz to 1 MHz. An external synchronization signal that is higher in frequency than the programmed frequency can be applied to this pin through a small coupling capacitor. The RT resistor to ground is required even when using external synchronization.
6	GND	Ground	Ground return
7	COMP	Output of the internal error amplifier	The loop compensation network must be connected between this pin and the FB pin.
8	FB	Feedback signal from the regulated output	This pin is connected to the inverting input of the internal error amplifier. The regulation threshold is 1.205 V.
9	OUT	Output voltage connection	Connect directly to the regulated output voltage.
10	DITH	Frequency Dithering (LM25088-1 Only)	A capacitor connected between the DITH pin and GND is charged and discharged by 27-µA current sources. As the voltage on the DITH pin ramps up and down, the oscillator frequency is modulated between –5% to +5% of the nominal frequency set by the RT resistor. Grounding the DITH pin disables frequency dithering mode.
10	RES	Hiccup Mode Restart (LM25088-2 Only)	The RES pin is normally connected to an external capacitor that sets the timing for hiccup mode current limiting. In normal operation, a 25-µA current source discharges the RES pin capacitor to ground. If the cycle-by-cycle current limit threshold is exceeded during any PWM cycle, the current sink is disabled and RES capacitor is charged by an internal 50-µA current. If the RES voltage reaches 1.2 V, the HG pin gate drive signal is disabled and the RES pin capacitor is discharged by a 1-µA current sink. Normal operation resumes when the RES pin falls below 0.2 V.
11	CSG	Current sense ground	Low-side reference for the current sense resistor
12	CS	Current sense	Current measurement connection for the re-circulating diode. An external sense resistor and an internal sample or hold circuit sense the diode current at the conclusion of the buck switch off time. This current measurement provides the DC offset level for the emulated current ramp.
13	SW	Switching node	Connect to the source terminal of the external MOSFET switch.
14	HG	High Gate	Connect to the gate terminal of the external MOSFET switch.
15	BOOT	Input for bootstrap capacitor	An external capacitor is required between the BOOT and the SW pins to provide bias to the MOSFET gate driver. The capacitor is charged from VCC through an internal diode during the off time of the buck switch.
16	VCC	Output of the bias regulator	VCC tracks VIN up to the regulation level (7.8 V typical). A 0.1-µF to 10-µF ceramic decoupling capacitor is required. An external voltage between 8.3 V and 13 V can be applied to this pin to reduce internal power dissipation.
17	EP	Exposed Pad	Exposed pad of the package. Electrically isolated. Must be soldered to the ground plane to reduce thermal resistance.