lx1670 Microsemi Corporation, lx1670 Datasheet - Page 6

• Manufacturer Part Number: lx1670
• Description: 5 - Bit Programmable Votage Reference
• Manufacturer: Microsemi Corporation

LX1670
6
UNDER-VOLTAGE LOCKOUT
This function keeps order to the IC until the power supply voltage
reaches 85% of its nominal value. The output voltage is pulled low
and P
voltage crosses 85%, the output voltage, VIDO, is released, and
P
microprocessor's power supply) is within ±7% of VIDO, P
released. The comparator has hysteresis to prevent transient
oscillation.
4-BIT DAC and 5th-BIT SCALER
This function generates a precise voltage from a binary, 5-bit
digital word VID [0:4]. It uses a 4-bit, binary weighted current
DAC, driving a precise current to voltage converter. This voltage
is then op-amp buffered and sent out. The scaling is accomplished
by multiplexing the buffer op-amp. The resulting transfer function
is:
The zero-scale output voltage, full-scale output voltage and the
scale factor are all trimmed on-chip using fusable links.
GOOD
VIDO (D0,D1,D2,D3) =
VIDO (D0,D1,D2,D3) =
for the code VIDO < 1.8V will be blocked and VIDO = 0.
(2.00 + 0.1 * (1 * D0 + 2 * D1 + 4 * D2 + 8 * D3))
(2.00 + 0.6 + 0.1 * (1 * D0 + 2 * D1 + 4 * D2 + 8 * D3)) * 0.5
GOOD
continues to be pulled low.
and OV
OUT
are pulled low. Once the power supply
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
5 - B
I T
P
R O D U C T I O N
P
When V
R O G R A M M A B L E
T H E O R Y O F O P E R A T I O N
for D4 = 1
for D4 = 0
SENSE
GOOD
(the
is
D
V
OVER- / UNDER-VOLTAGE COMPARATORS
This function generates an open collector Power Good signal
when V
OVER-VOLTAGE PROTECTION
This function generates an OV
higher than VIDO. This voltage can be used to drive an external
SCR.
CHIP ENABLE
This function disables the chip when low. VIDO, P
are all pulled low. When ENABLE is high, the chip's state is then
determined by the other functions.
BLANK ENABLE
This function will disable VIDO for codes with voltages below
1.80V when this pin is high. When pulled low, this function will
allow VIDO to accept codes for voltages of 1.30 to 3.50V.
A T A
O L T A G E
SENSE
S
is within ±7% of VIDO.
R
H E E T
E F E R E N C E
OUT
voltage signal when V
GOOD
SENSE
and OV
Copyright © 1997
Rev. 1.0
is 15%
OUT
7/97