Rainbow Electronics MAX769 - Manual (Page 8)

MAX769
2 or 3-Cell, Step-Up/Down,
Two-Way Pager System IC
8 _______________________________________________________________________________________
LB0
TO S1
AND S2
LBI
CH0
0.6V
CH0
RUN/
COAST
OV0–OV4
SERIAL
I/O
CH1
CH2
S1
7
DAC0–DAC7
RESET
CONTROL
V FEEDBACK
CHARGE
NICD
OR
BACKUP
REGULATOR
PWM
(PFM IN
COAST)
CHG/REG
+
–
CP LB
CP0
CP1
CP2
N
6
11
2 5 27
SDO SDI SCL
3 26
9
REF
0.6V
1 µ F
10 µ A
1.0V
REG3
1 µ F
8
5
RSIN 10
17 18 19 16 15
20
21
14
DR1 DR2IN DR2 AGND DRGND
N
1.8 Ω
1.8 Ω
REG2 ON
REG3 ON
N N
P
P
7
–
+
+
–
+
–
FROM
NICD
FROM
BATTERY
7-BIT
CH
DAC
S2
5
REG2
REG1
R2IN
C OFS
0.1 µ F
OFS
NICD
R OFS
15k
10 µ F
10 µ F
OUT
SYNC
FILT
PGND
LX2
LX1
BATT
P
N
N
P
2- OR 3-CELL
BATTERY IN
L1
68
µ H
22 µ F
47 µ F
-
+
A OUT
+
–
CS
1.28V
REFERENCE
1.0V
–
+
BACKUP
REGULATOR
CLAMP ON WHEN
OV4 = 1
3.3V
CLAMP
1mA/15mA
3.3V
P
–
+
–
+
A R1
A R2
A R3
22
23
24
25
13 1nF
22nF
10k
12
28
X7
PLL
LBO
RSO
MAX769
4
1
CP RS
Figure 1. MAX769 Block Diagram