ST ALTAIR05T-800 User Manual

ALTAIR05T-800

Off-line all-primary-sensing switching regulator

Features

■Constant voltage and constant current output regulation (CV/CC) with no optocoupler

■Tight regulation also in presence of heavy load transients

■800 V avalanche rugged internal power section

■Quasi-resonant (QR) operation

■Low standby power consumption

■Automatic self-supply

■Input voltage feedforward for mainsindependent cc regulation

■Output cable drop compensation

■SO16 package

SO16N

Applications

■AC-DC chargers for mobile phones and other hand-held equipments

■Compact SMPS that requires a precise current and/or voltage regulation

Description

ALTAIR05T-800 is a high-voltage all-primary sensing switcher intended for operating directly from the rectified mains with minimum external parts. It combines a high-performance lowvoltage PWM controller chip and an 800 V avalanche-rugged power section in the same package.

Figure 1. Block diagram

										+Vout
								+Vin
	Vcc									Istart-up
						Internal supply bus	SUPPLY			DRAIN
		PROTECTION &
						Vref
		FEEDFORWARD					& UVLO
			LOGIC						UVLO
			Prot	IFF		BLANKING
						TIME
	CDC		Iout	Vc	3.3 V		STARTER			Intern.
										supply
		ESTIMATE
	Rcdc					TURN-ON				bus
								S
Rzcd						LOGIC
	ZCD/FB
			DEMAG			Vc			Q
						-
			LOGIC		R		LEB	R
						+
				S					S	UVLO
	Rfb				Q
						Iref	1 V		Q
				R					R
								-
						+
		S/H	-				IFF
								+
						-
			+						Prot
		2.5V					RFF
			COMP		IREF	GND				SOURCE
				Rcomp		Cref
										Rsense
				Ccomp
October 2010						Doc ID 17957 Rev 1				1/28
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Contents	ALTAIR05T-800

Contents

1	Device description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		. 3
2	Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		4
3	Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		6
	3.1	Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
	3.2	Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
4	Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		7
5	Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		11
	5.1	Power section and gate driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	12
	5.2	High-voltage start-up generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	12
	5.3	Zero current detection and triggering block . . . . . . . . . . . . . . . . . . . . . . .	13
	5.4	Constant voltage operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	15
	5.5	Constant current operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	15
	5.6	Voltage feedforward block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	17
	5.7	Cable drop compensation (CDC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	18
	5.8	Burst-mode operation at no load or very light load . . . . . . . . . . . . . . . . . .	20
	5.9	Soft-start and starter block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	20
	5.10	Hiccup mode OCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	21
	5.11	Layout recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	21
6	Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		23
7	Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		24
8	Order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		26
9	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		27

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ALTAIR05T-800	Device description

1 Device description

The device combines two silicon in the same package: a low voltage PWM controller and an 800 V avalanche rugged power section.

The controller chip is a current-mode specifically designed for offline quasi-resonant flyback converters.

The device features a unique characteristic: it is capable of providing constant output voltage (CV) and constant output current (CC) regulation using primary-sensing feedback. This eliminates the need for the optocoupler, the secondary voltage reference, as well as the current sensor, still maintaining quite accurate regulation also in presence of heavy load transients. Additionally, it is possible to compensate the voltage drop on the output cable, so as to improve CV regulation on the external accessible terminals.

Quasi-resonant operation is guaranted by means of a transformer demagnetization sensing input that turns on the power section. The same input serves also the output voltage monitor, to perform CV regulation, and the input voltage monitor, to achieve mainsindependent CC regulation (line voltage feedforward).

The maximum switching frequency is top-limited below 166 kHz, so that at medium-light load a special function automatically lowers the operating frequency still maintaining the valley switching operation. At very light load, the device enters a controlled burst-mode operation that, along with the built-in high-voltage start-up circuit and the low operating current, helps minimize the standby power.

Although an auxiliary winding is required in the transformer to correctly perform CV/CC regulation, the chip is able to power itself directly from the rectified mains. This is useful especially during CC regulation, where the flyback voltage generated by the winding drops below UVLO threshold. However, if ultra-low no-load input consumption is required to comply with the most stringent energy-saving recommendations, then the device needs to be powered via the auxiliary winding.

In addition to these functions that optimize power handling under different operating conditions, the device offers protection features that considerably increase end-product’s safety and reliability: auxiliary winding disconnection - or brownout – detection and shorted secondary rectifier - or transformer’s saturation – detection. All of them are auto restart mode.

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Pin connection	ALTAIR05T-800

2 Pin connection

Figure 2. Pin connection (top view)

SOURCE	1	16	DRAIN
SOURCE	2	15	DRAIN
Vcc	3	14	DRAIN
GND	4	13	DRAIN
IREF	5	12	N.C.
ZCD/FB	6	11	N.A.
COMP	7	10	N.A.
CDC	8	9	N.A.

	Note:	The copper area for heat dissipation has to be designed under the drain pins
	Table 1.	Pin functions
	N.	Name	Function
			Power section source and input to the PWM comparator. The current flowing in the MOSFET
			is sensed through a resistor connected between the pin and GND. The resulting voltage is
	1, 2	SOURCE	compared with an internal reference (0.75V max.) to determine MOSFET’s turn-off. The pin
			is equipped with 250 ns blanking time after the gate-drive output goes high for improved
			noise immunity. If a second comparison level located at 1V is exceeded the IC is stopped and
			restarted after Vcc has dropped below 5V.
			Supply Voltage of the device. An electrolytic capacitor, connected between this pin and
			ground, is initially charged by the internal high-voltage start-up generator; when the device is
	3	Vcc	running the same generator keeps it charged in case the voltage supplied by the auxiliary
			winding is not sufficient. This feature is disabled in case a protection is tripped. Sometimes a
			small bypass capacitor (0.1 µF typ.) to GND might be useful to get a clean bias voltage for
			the signal part of the IC.
			Ground. Current return for both the signal part of the IC and the gate drive. All of the ground
	4	GND	connections of the bias components should be tied to a trace going to this pin and kept
			separate from any pulsed current return.
			CC regulation loop reference voltage. An external capacitor has to be connected between
	5	IREF	this pin and GND. An internal circuit develops a voltage on this capacitor that is used as the
			reference for the MOSFET’s peak drain current during CC regulation. The voltage is
			automatically adjusted to keep the average output current constant.

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	ALTAIR05T-800		Pin connection
	Table 1.	Pin functions (continued)
	N.	Name	Function
			Transformer’s demagnetization sensing for quasi-resonant operation. Input/output voltage
			monitor. A negative-going edge triggers MOSFET’s turn-on. The current sourced by the pin
			during ON-time is monitored to get an image of the input voltage to the converter, in order to
			compensate the internal delay of the current sensing circuit and achieve a CC regulation
			independent of the mains voltage. If this current does not exceed 50µA, either a floating pin
	6	ZCD/FB	or an abnormally low input voltage is assumed, the device is stopped and restarted after Vcc
			has dropped below 5V. Still, the pin voltage is sampled-and-held right at the end of
			transformer’s demagnetization to get an accurate image of the output voltage to be fed to the
			inverting input of the internal, transconductance-type, error amplifier, whose non-inverting
			input is referenced to 2.5V. Please note that the maximum IZCD/FB sunk/sourced current has
			to not exceed ±2 mA (AMR) in all the Vin range conditions (85-265 Vac). No capacitor is
			allowed between the pin and the auxiliary transformer.
			Output of the internal transconductance error amplifier. The compensation network is placed
	7	COMP	between this pin and GND to achieve stability and good dynamic performance of the voltage
			control loop.
			Cable drop compensation input. During CV regulation this pin, capable of sinking current,
			provides a voltage lower than the internal reference voltage (2.5V) by an amount proportional
	8	CDC	to the dc load current. By connecting a resistor between this pin and ZCD/FB, the CV
			regulation setpoint is increased proportionally. This allows that the voltage drop across the
			output cable be compensated and, ideally, that zero load regulation at the externally available
			terminals be achieved. Leave the pin open if the function is not used.
	9-11	N.A	Not available. These pins must be left not connected
	12	N.C	Not internally connected. Provision for clearance on the PCB to meet safety requirements.
			Drain connection of the internal power section. The internal high-voltage start-up generator
	13 to 16	DRAIN	sinks current from this pin as well. Pins connected to the internal metal frame to facilitate
			heat dissipation.

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Maximum ratings	ALTAIR05T-800

3 Maximum ratings

3.1Absolute maximum ratings

Table 2.	Absolute maximum ratings
Symbol	Pin	Parameter	Value	Unit
VDS	1,2, 13-16	Drain-to-source (ground) voltage	-1 to 800	V
ID	1,2, 13-16	Drain current	1	A
Eav	1,2, 13-16	Single pulse avalanche energy (Tj = 25°C, ID = 1A)	50	mJ
Vcc	3	Supply voltage (Icc < 25mA)	Self limiting	V
IZCD/FB	6	Zero current detector current	±2	mA
---	7, 8	Analog inputs and outputs	-0.3 to 3.6	V
ICDC	8	Maximum sunk current	200	µA
Ptot		Power dissipation @TA = 50°C	0.9	W
Tj		Junction temperature range	-25 to 150	°C
Tstg		Storage temperature	-55 to 150	°C

3.2Thermal data

	Table 3.	Thermal data
	Symbol	Parameter	Max. value	Unit
	Rth j-pin	Thermal resistance, junction-to-pin	10	°C/W
	Rth j-amb	Thermal resistance, junction-to-ambient	110

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ALTAIR05T-800	Electrical characteristics

4 Electrical characteristics

(TJ = -25 to 125 °C, Vcc = 14 V; unless otherwise specified)

	Table 4.	Electrical characteristics
	Symbol	Parameter	Test condition	Min.	Typ.	Max.	Unit
	Power section
	V(BR)DSS	Drain-source breakdown	ID< 100 µA; Tj = 25 °C	800			V
	IDSS	Off state drain current	VDS = 750 V; Tj = 125 °C			80	µA
			(See Figure 4 and note)
	RDS(on)	Drain-source ON-state resistance	Id=100 mA; Tj = 25 °C		11	14	Ω
			Id=100 mA; Tj = 125 °C		22	28
	Coss	Effective (energy-related) output capacitance	(See Figure 3)
	High-voltage start-up generator
	VStart	Min. Drain start voltage	Icharge < 100 µA	40	50	60	V
	Icharge	Vcc startup charge current	VDRAIN> VStart; VCC<VCCOn	4	5.5	7	mA
			Tj = 25 °C
	VCCrestart	Vcc restart voltage (Vcc falling)	(1)	9.5	10.5	11.5	V
			After protection tripping		5
	Supply voltage
	Vcc	Operating range	After turn-on	11.5		23	V
	VccOn	Turn-on threshold	(1)	12	13	14	V
	VccOff	Turn-off threshold	(1)	9	10	11	V
	VZ	Zener voltage	Icc = 20 mA	23	25	27	V
	Supply current
	Iccstart-up	Start-up current	(See Figure 5)		200	300	µA
	Iq	Quiescent current	(See Figure 6)		1	1.4	mA
	Icc	Operating supply current @ 50 kHz	(See Figure 7)		1.4	1.7	mA
	Iq(fault)	Fault quiescent current	During hiccup and brownout		250	350	µA
			(See Figure 8)
	Start-up timer
	TSTART	Start timer period		100	125	175	µs
	TRESTART	Restart timer period during burst mode		400	500	700	µs
	Zero current detector
	IZCDb	Input bias current	VZCD = 0.1 to 3 V		0.1	1	µA
	VZCDH	Upper clamp voltage	IZCD = 1 mA	3.0	3.3	3.6	V

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Electrical characteristics								ALTAIR05T-800
Table 4.		Electrical characteristics (continued)
Symbol		Parameter				Test condition	Min.	Typ.	Max.	Unit
VZCDL		Lower clamp voltage		IZCD = - 1 mA			-90	-60	-30	mV
VZCDA		Arming voltage		positive-going edge			100	110	120	mV
VZCDT		Triggering voltage		negative-going edge			50	60	70	mV
IZCDON		Min. source current during MOSFET ON-time					-25	-50	-75	µA
TBLANK		Trigger blanking time after MOSFET’s turn-off		VCOMP ≥ 1.3V				6		µs
				VCOMP = 0.9V				30
Line feedforward
RFF		Equivalent feedforward resistor		IZCD = 1mA				45		Ω
Transconductance error amplifier
				Tj = 25°C (1)			2.46	2.5	2.54
VREF		Voltage reference								V
				Tj = -25 to 125°C and			2.42		2.58
				Vcc=12V to 23V (1)
gm		Transconductance		∆ICOMP = ±10 µA			1.3	2.2	3.2	mS
				VCOMP = 1.65 V
Gv		Voltage gain		Open loop				73		dB
GB		Gain-bandwidth product						500		KHz
ICOMP		Source current		VZCD = 2.3V, VCOMP = 1.65V			70	100		µA
		Sink current		VZCD = 2.7V, VCOMP = 1.65V			400	750		µA
VCOMPH		Upper COMP voltage		VZCD = 2.3 V				2.7		V
VCOMPL		Lower COMP voltage		VZCD = 2.7 V				0.7		V
VCOMPBM		Burst-mode threshold						1		V
Hys		Burst-mode hysteresis						65		mV
CDC function
VCDC		CDC voltage reference		VCOMP = 1.1V, ICDC = 1µA (1)			2.4	2.5	2.6	V
Current reference
VIREFx		Maximum value				(1)	1.5	1.6	1.7	V
				VCOMP = VCOMPL
VCREF		Current reference voltage					0.192	0.2	0.208	V
Current sense
tLEB		Leading-edge blanking					200	250	300	ns
td(H-L)		Delay-to-output						300		ns
V	CSx	Max. clamp value		dV	cs	/d = 200 mV/µs (1)	0.7	0.75	0.8	V
						t
VCSdis		Hiccup-mode OCP level		(1)			0.92	1	1.08	V

1. Parameters tracking each other

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ALTAIR05T-800	Electrical characteristics
Figure 3.	COSS output capacitance variation

COSS (pF)
500
400
300
200
100
0
0	25	50	75	100	125	150

VDS (V)

Figure 4. Off state drain and source current test circuit

14 V	A	Ids s

C D C		VD D		D R AI N
2. 5V	+		C U R R EN T	Vin
	-		C ON TR OL	75 0V
FB /ZC D
	C OMP	IR E F	GN D	SOU R C E

Note: The measured IDSS is the sum between the current across the start-up resistor and the effective MOSFET’s off state drain current.

Figure 5. Start-up current test circuit

Ic cstart-up A							1 1.8 V

CD C		V D D		D R AIN
2. 5V	+		C U R R EN T
	-		C ON TR OL
FB/ ZC D
	C OMP	IR EF	GN D	SOU RC E

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