ES1022SI datasheet(7/14 Pages) ALTERA

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Enpirion Power Datasheet ES1022SI Adjustable Quad Sequencer

May 2014

Altera Corporation

reference voltage, (VTIME_VTH) the EN_A output is released out of its reset state. The capacitor value for a desired delay (±10%)

to EN_A once VIN and SEQ_EN where applicable has been satisfied is determined by:

CTIME = tVINSEQpd/770kΩ

Once EN_A reaches VTIME_VTH, the TIME pin is pulled low in preparation for a sequenced off signal via SEQ_EN. At this

time, the sequencing of the subsequent outputs is started. EN_B is released out of reset after a programmable time, then

EN_C, then EN_D, all with their own programmed delay times.

The subsequent delay times are programmed with a single external resistor for each EN output providing maximum

flexibility to the designer through the choice of the resistor value connected from TDLY_AB, TDLY_BC and TDLY_CD pins

to GND. The resistor values determine the charge and discharge rate of an internal capacitor comprising an RC time

constant for an oscillator whose output is fed into a counter generating the timing delay to EN output sequencing.

The RTX value for a given delay time is defined as:

RTX = tdel/1667nF

An Advanced Tutorial on Setting UV and OV Levels

This section discusses in additional detail the nuances of setting the UV and OV levels, providing more insight into the

ES1022SI than the earlier text.

The following equation set can alternatively be used to work out ideal values for a 3 resistor divider string of Ru, Rm and Rl.

These equations assume that VREF is the center point between VUVRvth and VUVFvth (i.e. (VUVRvth + VUVFvth)/2 = 1.17V), Iload

is the load current in the resistor string (i.e. VIN /(Ru + Rm + Rl)), VIN is the nominal input voltage and Vtol is the acceptable

voltage tolerance, such that the UV and OV thresholds are centered at VIN ± Vtol. The actual acceptable voltage window will

also be affected by the hysteresis at the UV and OV pins. This hysteresis is amplified by the resistor string such that the

hysteresis at the top of the string is:

Vhys = VUVhys x VOUT/VREF

This means that the VIN ± Vtol thresholds will exhibit hysteresis resulting in thresholds of VIN + Vtol ± Vhys/2 and VIN

- Vtol ± Vhys/2.

There is a window between the VIN rising UV threshold and the VIN falling OV threshold where the input level is

guaranteed not to be detected as a fault. This window exists between the limits VIN ± (Vtol - Vhys/2). There is an

extension of this window in each direction up to VIN ± (Vtol + Vhys/2), where the voltage may or may not be detected

as a fault, depending on the direction from which it is approached. These two equations may be used to determine the

required value of Vtol for a given system. For example, if VIN is 12V, Vhys = (0.1 x 12)/1.17 = 1.03V. If VIN must remain

within 12V ± 1.5V, Vtol = 1.5 - 1.03/2 = 0.99V. This will give a window of 12 ±0.48V where the system is guaranteed not

to be in fault and a limit of 12 ±1.5V beyond which the system is guaranteed to be in fault.

It is wise to check both these voltages, for if the latter is made to tight, the former will cease to exist. This point comes when

Vtol < Vhys/2 and results from the fact that the acceptable window for the OV pin no longer aligns with the acceptable

window for the UV pin. In this case, the application will have to be changed such that UV and OV are provided separate

resistor strings. In this case, the UV and OV thresholds can be individually controlled by adjusting the relevant divider.

The previous example will give voltage thresholds of:

with VIN rising

UVr = VIN - Vtol + Vhys/2 = 11.5V and

OVr = VIN + Vtol + Vhys/2 = 13.5V

with VIN falling

Ovf = VIN + Vtol - Vhys/2 = 12.5V and

UVf = VIN - Vtol - Vhys/2 = 10.5V.

So with a single three resistor string, the resistor values can be calculated as:

Rl = (VREF/Iload) (1 - Vtol/VIN)

Rm = 2(VREF x Vtol)/(VIN x Iload)

Ru = 1/Iload x (VIN - VREF (1+Vtol/VIN))

10037

May 28, 2014

Rev A

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