SN6505B

The SN6505B is an electronic component from Texas Instruments. View the full SN6505B datasheet below including electrical characteristics, absolute maximum ratings.

Manufacturer

Texas Instruments

Overview

When Q2 conducts, Q1 goes high-impedance and the voltage polarities at the primary and secondary reverse. Now the lower end of the primary presents the open end with a 2×VIN potential against ground. In this case CR2 is forward biased while CR1 is reverse biased and current flows from the lower secondary end through CR2, charging the capacitor and returning through the load to the center-tap.

Pin Configuration

Pin Functions

Pin Functions

PIN	PIN	PIN	DESCRIPTION
NAME	NO.	TYPE	DESCRIPTION
D1	1	O	Open drain output of the first power MOSFETs. Typically connected to the outer terminals of the center tap transformer. Because large currents flow through these pins, their external traces should be kept short.
V CC	2	P	This is the device supply pin. It should be bypassed with a 4.7 μ F or greater, low ESR capacitor. When V CC ≤ 2.25 V, an internal undervoltage lockout circuit trips and turns both outputs off.
D2	3	O	Open drain output of the second power MOSFETs. Typically connected to the outer terminals of the center tap transformer. Because large currents flow through these pins, their external traces should be kept short.
GND	4	P	GND is connected to the source of the power MOSFET switches via an internal sense circuit. Because large currents flow through it, the GND terminals must be connected to a low-inductance quality ground plane.
EN	5	I	The EN pin turns the device on or off. Grounding or leaving this pin floating disables all internal circuitry. If unused this pin should be tied directly to V CC .
CLK	6	I	This pin is used to run the SN6505 with external clock. Internally it is pulled down to GND . If valid clock is not detected on this pin, the SN6505 shifts automatically to internal clock.

Electrical Characteristics

over full-range of recommended operating conditions, unless otherwise noted. All typical values are at TA = 25°C, VCC = 5 V.

PARAMETER	PARAMETER	TEST CONDITIONS	MIN	TYP	MAX	UNIT
VOLTAGE SUPPLY	VOLTAGE SUPPLY	VOLTAGE SUPPLY	VOLTAGE SUPPLY	VOLTAGE SUPPLY	VOLTAGE SUPPLY	VOLTAGE SUPPLY
I (VCC)	Supply Current (2.8 V < VC C < 5.5) (SN6505A)	R L = 50 Ω		1	1.4	mA
I (VCC)	Supply Current (2.8 V < VC C < 5.5) (SN6505B)			1.56	2.3	mA
I IH	Leakage Current on EN and CLK pin	EN / CLK = V CC		10	20	μA
I DIS	V CC current for EN = 0			0.1		μA
I LKG(D1) I LKG(D2)	Leakage Current on D1,D2 for EN=0	Voltage of D1,D2 = V CC		0.1		μA
V CC+ (UVLO)	Positive-going UVLO threshold				2.25	V
V CC- (UVLO)	Negative-going UVLO threshold		1.7			V
V HYS (UVLO1)	UVLO threshold hysteresis			0.3		V
V IN(ON)	EN, CLK pin logic high threshold				0.7	V CC
V IN(OFF)	EN, CLK pin logic low threshold		0.3			V CC
V IN(HYS)	EN, CLK pin threshold hysteresis			0.2		V CC
CLK	CLK	CLK	CLK	CLK	CLK	CLK
F SW	D1, D2 average switching Frequency (SN6505A)	R L = 50 Ω to V CC ; Refer to Figure 12	138	160	203	Khz
F SW	D1, D2 average switching Frequency (SN6505B)	R L = 50 Ω to V CC ; Refer to Figure 12.	363	424	517	kHz
F (EXT)	External clock frequency on CLK pin (SN6505A)		100		600	kHz
F (EXT)	External clock frequency on CLK pin (SN6505B)		100		1600	kHz
OUTPUT STAGE	OUTPUT STAGE	OUTPUT STAGE	OUTPUT STAGE	OUTPUT STAGE	OUTPUT STAGE	OUTPUT STAGE
DMM	Average ON time mismatch between D1 and D2	R L = 50 Ω		0%
R (ON)	Output switch on resistance	V CC = 4.5 V, ID1,ID2 = 1 A		0.16	0.25	Ω
		V CC = 2.8 V, ID1,ID2 = 1 A		0.19	0.31	Ω
		V CC = 2.25 V, ID1,ID2 = 0.5 A		0.21	0.45	Ω

Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted) (1) .All typical values are at TA = 25°C, VCC = 5 V.

		MIN	MAX	UNIT
Supply voltage (2)	V CC	-0.5	6	V
Voltage	EN, CLK	-0.5	V CC + 0.5 (3)
Output switch voltage	D1, D2		16	V
Peak output switch current	I (D1)Pk , I (D2)Pk		2.4	A
Junction temperature, T J	Junction temperature, T J	-55	150	°C
Storage temperature range, T stg	Storage temperature range, T stg	-65	150	°C

(2) All voltage values except differential I/O bus voltages are with respect to the local ground terminal (GND) and are peak voltage values.

(3) Maximum voltage of 6V.

Recommended Operating Conditions

			MIN	MAX	UNIT
V CC	Supply voltage		2.25	5.5	V
I D1 , I D2	Output switch current - Primary side	2.25 V < V CC < 2.8 V		0.75	A
	Ambient temperature	2.8 V < V CC < 5.5 V		1	A
T A			-55	125	°C

Thermal Information

THERMAL METRIC (1)	THERMAL METRIC (1)	DW (SOIC) 16 PINS	UNIT
R θ JA	Junction-to-ambient thermal resistance	137.7	°C/W
R θ JC(top)	Junction-to-case (top) thermal resistance	57.7	°C/W
R θ JB	Junction-to-board thermal resistance	46.0	°C/W
ψ JT	Junction-to-top characterization parameter	13.4	°C/W
ψ JB	Junction-to-board characterization parameter	44.9	°C/W
R θ JC(bottom)	Junction-to-case(bottom) thermal resistance	N/A	°C/W

Typical Application

The SN6505 is a transformer driver designed for low-cost, small form-factor, isolated DC-DC converters utilizing the push-pull topology. The device includes an oscillator that feeds a gate-drive circuit. The gate-drive, comprising a frequency divider and a break-before-make (BBM) logic, provides two complementary output signals which alternately turn the two output transistors on and off.

Figure 16. SN6505 Block Diagram And Output Timing With Break-Before-Make Action

The output frequency of the oscillator is divided down by an asynchronous divider that provides two complementary output signals, S and S, with a 50% duty cycle. A subsequent break-before-make logic inserts a dead-time between the high-pulses of the two signals. The resulting output signals, G1 and G2, present the gatedrive signals for the output transistors Q1 and Q2. As shown in Figure 17, before either one of the gates can assume logic high, there must be a short time period during which both signals are low and both transistors are high-impedance. This short period, known as break-before-make time, is required to avoid shorting out both ends of the primary.

Figure 17. Detailed Output Signal Waveforms

Figure 16. SN6505 Block Diagram And Output Timing With Break-Before-Make Action

Related Variants

The following components are covered by the same datasheet.

Part Number	Manufacturer	Package
SN6505	Texas Instruments	—
SN6505A	Texas Instruments	—
SN6505ADBVR	Texas Instruments	—
SN6505ADBVT	Texas Instruments	—
SN6505BDBVR	Texas Instruments	SOT-23-6
SN6505BDBVT	Texas Instruments

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