參數(shù)資料
型號: LLTC1142HV
廠商: Linear Technology Corporation
元件分類: 基準(zhǔn)電壓源/電流源
英文描述: RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
中文描述: 抗輻射高效,5安培開關(guān)穩(wěn)壓器
文件頁數(shù): 8/20頁
文件大?。?/td> 261K
代理商: LLTC1142HV
8
LTC1142/LTC1142L/LTC1142HV
The LTC1142 series consists of two individual regulator
blocks, each using current mode, constant off-time archi-
tectures to synchronously switch an external pair of
complementary power MOSFETs. The two regulators are
internally set to provide output voltages of 3.3V and 5V for
the LTC1142. The LTC1142HV-ADJ/LTC1142L-ADJ are
configured to provide two user selectable output voltages,
each set by external resistor dividers. Operating fre-
quency is individually set on each section by the external
capacitors at C
T
, Pins 11 and 25.
The output voltage is sensed by an internal voltage divider
connected to Sense
, Pin 28 (14) (LTC1142) or external
divider returned to V
FB
, Pin 2 (16) (LTC1142-ADJ). A
voltage comparator V and a gain block G compare the
divided output voltage with a reference voltage of 1.25V.
To optimize efficiency, the LTC1142 series automatically
switches between two modes of operation, Burst Mode
and continuous mode. The voltage comparator is the
primary control element when the device is in Burst Mode
operation, while the gain block controls the output voltage
in continuous mode.
During the switch “ON” cycle in continuous mode, current
comparator C monitors the voltage between Pins 1 (15)
and 28 (14) connected across an external shunt in series
with the inductor. When the voltage across the shunt
reaches its threshold value, the PDrive output is switched
to V
IN
, turning off the P-channel MOSFET. The timing
capacitor connected to Pin 25 (11) is now allowed to
discharge at a rate determined by the off-time controller.
The discharge current is made proportional to the output
voltage [measured by Pin 28 (14)] to model the inductor
current, which decays at a rate that is also proportional to
the output voltage. While the timing capacitor is discharg-
ing, the NDrive output goes to V
IN
, turning on the N-channel
MOSFET.
When the voltage on the timing capacitor has discharged
past V
TH1
, comparator T trips, setting the flip-flop. This
causes the NDrive output to go low (turning off the
N-channel MOSFET) and the PDrive output to also go low
(turning the P-channel MOSFET back on). The cycle then
repeats.
Refer to Functional Diagram
Only one regulator block shown. Pin numbers are for 3.3V (5V) sections for LTC1142/LTC1142HV,
and V
OUT1
(V
OUT2
) for LTC1142L-ADJ/LTC1142HV-ADJ.
FU
W
OPERATIOU
+
+
REFERENCE
24(10)
23(9)
6(20)
4(18)
2(16)
PGND
NDRIVE
PDRIVE
V
IN
+
V
+
C
25mV TO 150mV
+
1(15)
V
OS
26(12)
2(16)
SHDN
INTV
CC
1.25V
5pF
G
27(13)
I
TH
Q
R
S
V
IN
SENSE
OFF-TIME
CONTROL
25(11)
C
T
13k
+
S
SLEEP
V
TH1
T
SENSE
+
V
TH2
PIN NUMBERS FOR
LTC1142, LTC1142HV
PIN NUMBERS
FOR LTC1142L-ADJ
LTC1142HV-ADJ
LTC1142-ADJ
3(17)
LTC1142L-ADJ
LTC1142HV-ADJ
4(18)
LTC1142L-ADJ
LTC1142HV-ADJ
2(16)
LTC1142L-ADJ, LTC1142HV-ADJ: 5(19)
LTC1142L-ADJ
LTC1142HV-ADJ
3(17)
3(17)
SGND
100k
28(14)
SENSE
1142 BD
NC/ADJ
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